Security algorithm selection in communication network environment

Abstract

A method comprises sending, from UE 102 to a network entity such as AMF 106, a message indicating a set of security algorithms supported by the UE, a first and at least a second subset of the set being configured with a first and at least a second key length respectively. The UE receives a second message indicating an algorithm from the set, the algorithm having been selected by the network entity, and being one having the longest key length supported by the communication network among the first and the at least a second key length. In a further method, a radio access entity 104 (e.g. gNB) receives a message from the network entity indicating the set of algorithms supported by the UE, and the selecting the algorithm and the sending of the second message are done by the radio access entity. Further apparatus comprises means from coordinating with an entity or device to utilize an extended length message authentication code (MAC) when performing an access stratum security mode command procedure, and means for utilizing the code. In a first apparatus, coordination is with a radio access entity, and in a second apparatus it is with a UE.

Description

Field The field relates generally to communication networks, and more particularly, but not exclusively, to security management in such communication networks. Background This section introduces aspects that may be helpful in facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art. Fourth generation (4G) wireless mobile telecommunications technology, also known as Long Term Evolution (LTE) technology, was designed to provide high-capacity mobile multimedia with high data rates particularly for human interaction. Next generation or fifth generation (5G) technology is intended to be used not only for human interaction, but also for machine type communications in so-called Internet of Things (loT) networks. While 5G networks are intended to enable massive loT services (e.g., very large numbers of limited capacity devices) and mission-critical loT services (e.g., requiring high reliability), improvements over legacy mobile communication services are supported in the form of enhanced mobile broadband (eMBB) services providing improved wireless Internet access for mobile devices. In an example communication system, user equipment (5G UE in a 5G network or, more broadly, a UE) such as a mobile terminal (subscriber) communicates over an air interface with a base station or access point of an access network referred to as a 5G AN in a 5G network. The access point (e.g., gNB) is illustratively part of an access network of the communication system. For example, in a 5G network, the access network referred to as a 5G AN is described in 5G Technical Specification (TS) 23.501, entitled “Technical Specification Group Services and System Aspects; System Architecture for the 5G System,” and TS 23.502, entitled “Technical Specification Group Services and System Aspects; Procedures for the 5G System (5GS),” the disclosures of which are incorporated by reference herein in their entireties. In general, the access point (e.g., gNB) provides access for the UE to a core network (CN or 5GC), which then provides access for the UE to other UEs and / or a data network such as a packet data network (e.g., Internet). TS 23.501 goes on to define a 5G Service-Based Architecture (SBA) which models services as network functions (NFs) that communicate with each other using representational state transfer application programming interfaces (Restful APIs). Furthermore, 5G Technical Specification (TS) 33.501, entitled “Technical Specification Group Services and System Aspects; Security Architecture and Procedures for the 5G System,” the disclosure of which is incorporated by reference herein in its entirety, further describes security management details associated with a 5G network. Security management is an important consideration in any communication system. However, due to continuing attempts to improve the architectures and protocols associated with a 5G network in order to increase network efficiency and / or subscriber convenience, security management issues associated with user equipment can present a significant challenge. For example, implementing newer security algorithms in existing devices and networks is a technical challenge. Summary Illustrative embodiments provide techniques for security algorithm selection in a communication network environment. In one illustrative embodiment, a method comprises sending, from user equipment to a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length, The method further comprises receiving, at the user equipment, a second message indicating at least one security algorithm from the set of security algorithms, wherein the at least one security algorithm is one having the longest key length supported by the communication network among the first key length and the at least a second key length. In another illustrative embodiment, a method comprises receiving, from user equipment at a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length. The method further comprises selecting, by the network entity, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by a communication network to which the network entity belongs among the first key length and the at least a second key length. The method further comprises sending, from the network entity to the user equipment, a second message indicating the selected at least one security algorithm. In a further illustrative embodiment, a method comprises receiving, at a radio access entity from a network entity of a communication network, a first message indicating a set of security algorithms supported by user equipment with which the network entity has established a first security command mode context, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length. The method further comprises selecting, by the radio access entity for a second security command mode context, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by the communication network among the first key length and the at least a second key length. The method further comprises sending, from the radio access entity to the user equipment, a second message to the user equipment indicating the selected at least one security algorithm. In yet another illustrative embodiment, a method comprises coordinating with a radio access entity of a communication network to utilize an extended length message authentication code when performing an access stratum security mode command procedure. In still another illustrative embodiment, a method comprises coordinating with user equipment to utilize an extended length message authentication code when performing an access stratum security mode command procedure. Further illustrative embodiments are provided in the form of a non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to perform the above steps. Still further illustrative embodiments comprise an apparatus with a processor and a memory configured to perform the above steps. Advantageously, illustrative embodiments provide techniques for enabling selection among security algorithms with different key lengths (e.g., 128 bits, 256 bits) such that the most secure algorithm is selected based on the key length participants are configured to support. Still other illustrative embodiments enable selection of extended length message authentication codes (e.g., 32 bits, 64 bits). These and other features and advantages of embodiments described herein will become more apparent from the accompanying drawings and the following detailed description. Brief Description of the Drawings FIG. 1 illustrates a communication system with which one or more illustrative embodiments may be implemented. FIG. 2 illustrates user equipment and entities with which one or more illustrative embodiments may be implemented. FIG. 3 illustrates a procedure for security algorithm selection according to an illustrative embodiment. FIG. 4 illustrates non-access stratum information element data for user equipment security capabilities according to an illustrative embodiment. FIG. 5 illustrates further non-access stratum information element data associated with user equipment security capabilities according to an illustrative embodiment. FIGS. 6A through 6C illustrate non-access stratum security algorithm information element data associated according to an illustrative embodiment. FIG. 7 illustrates network-side key derivation for a selected security algorithm according to an illustrative embodiment. FIG. 8 illustrates user equipment-side key derivation for a selected security algorithm according to an illustrative embodiment. FIG. 9 illustrates message authentication code derivation for a non-access stratum integrity protection algorithm according to an illustrative embodiment. FIG. 10 illustrates data ciphering for a non-access stratum confidentiality algorithm according to an illustrative embodiment. FIG. 11 illustrates information element data for user equipment security capabilities according to another illustrative embodiment. FIG. 12 illustrates a procedure for security algorithm selection according to another illustrative embodiment. FIG. 13 illustrates a procedure for extended length message authentication code selection according to an illustrative embodiment. Detailed Description Embodiments will be illustrated herein in conjunction with example communication systems and associated techniques for security management in communication systems. It should be understood, however, that the scope of the claims is not limited to particular types of communication systems and / or processes disclosed. Embodiments can be implemented in a wide variety of other types of communication systems, using alternative processes and operations. For example, although illustrated in the context of wireless cellular systems utilizing the 3rd Generation Partnership Project (3GPP) system elements such as a 3GPP next generation system (5G), the disclosed embodiments can be adapted in a straightforward manner to a variety of other types of communication systems such as 6G communication systems. In accordance with illustrative embodiments implemented in a 5G communication system environment, one or more 3GPP technical specifications (TS) and technical reports (TR) may provide further explanation of network elements / functions and / or operations that may interact with parts of the inventive solutions, e.g., the above-referenced 3GPP TS 23.501, TS 23.502, and TS 33.501. Other 3GPP TS / TR documents may provide other details that one of ordinary skill in the art will realize, for example, TS 24.501 entitled “3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3,” TS 38.323 entitled “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Packet Data Convergence Protocol (PDCP) specification,” TS 38.331 entitled, “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification,” TS 35.215 entitled, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Specification of the 3GPP confidentiality and integrity Algorithms UEA2 & UIA2; Document 1: UEA2 and UIA2 specifications,” TS 35.221 entitled, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Specification of the 3 GPP confidentiality and integrity Algorithms EEA3 & EIA3; Document 1: EEA3 and EIA3 specifications,” and TR 33.841 “3rd Generation Partnership Project; Technical Specification Group Services and Systems Aspects; Security aspects; Study on the Support of 256-bit Algorithms for 5G,” the disclosures of which are incorporated by reference herein in their entireties. Note that 3GPP TS / TR documents are non-limiting examples of communication network standards (e.g., specifications, procedures, reports, requirements, recommendations, and the like). However, while well-suited for 5G-related 3GPP standards, embodiments are not necessarily intended to be limited to any particular standards. It is to be understood that the term 5G network, and the like (e.g., 5G system, 5G communication system, 5G environment, 5G communication environment etc.), in some illustrative embodiments, may be understood to comprise all or part of an access network and all or part of a core network. However, the term 5G network, and the like, may also occasionally be used interchangeably herein with the term 5GC network, and the like, without any loss of generality, since one of ordinary skill in the art understands any distinctions. Prior to describing illustrative embodiments, a general description of certain main components of a 5G network will be described below in the context of FIGS. 1 and 2. FIG. 1 shows a communication system 100 within which illustrative embodiments are implemented. It is to be understood that the elements shown in communication system 100 are intended to represent some main functions provided within the system, e.g., control plane functions, user plane functions, etc. As such, the blocks shown in FIG. 1 reference specific elements in 5G networks that provide some of these main functions. However, other network elements may be used to implement some or all of the main functions represented. Also, it is to be understood that not all functions of a 5G network are depicted in FIG. 1. Rather, at least some functions that facilitate an explanation of illustrative embodiments are represented. Subsequent figures may depict some additional elements / functions (i.e., network entities). Accordingly, as shown, communication system 100 comprises user equipment (UE) 102 that communicates via an air interface 103 with an access point 104. It is to be understood that UE 102 may use one or more other types of access points (e.g., access functions, networks, etc.) to communicate with the 5GC network other than a gNB. By way of example only, the access point 104 may be any 5G access network (gNB), an untrusted non-3GPP access network that uses an Non-3GPP Interworking Function (N3IWF), a trusted non-3GPP network that uses a Trusted Non-3GPP Gateway Function (TNGF) or wireline access that uses a Wireline Access Gateway Function (W-AGF) or may correspond to a legacy access point (e.g., eNB). Furthermore, access point 104 may be a wireless local area network (WLAN) access point as will be further explained in illustrative embodiments described herein. The UE 102 may be a mobile station, and such a mobile station may comprise, by way of example, a mobile telephone, a computer, anloT device, or any other type of communication device. The term “user equipment” as used herein is therefore intended to be construed broadly, so as to encompass a variety of different types of mobile stations, subscriber stations or, more generally, communication devices, including examples such as a combination of a data card inserted in a laptop or other equipment such as a smart phone. Such communication devices are also intended to encompass devices commonly referred to as access terminals. In one illustrative embodiment, UE 102 is comprised of a Universal Integrated Circuit Card (UICC) part and a Mobile Equipment (ME) part. The UICC is the user-dependent part of the UE and contains at least one Universal Subscriber Identity Module (USIM) and appropriate application software. The USIM securely stores a permanent subscription identifier and its related key, which are used to uniquely identify and authenticate subscribers to access networks. The ME is the user-independent part of the UE and contains terminal equipment (TE) functions and various mobile termination (MT) functions. Alternative illustrative embodiments may not use UICC-based authentication, e.g., a Non-Public (Private) Network (NPN). Note that, in one example, the permanent subscription identifier is an International Mobile Subscriber Identity (IMSI) unique to the UE. In one embodiment, the IMSI is a fixed 15-digit length and consists of a 3-digit Mobile Country Code (MCC), a 3-digit Mobile Network Code (MNC), and a 9-digit Mobile Station Identification Number (MSIN). In a 5G communication system, an IMSI is referred to as a Subscription Permanent Identifier (SUPI). In the case of an IMSI as a SUPI, the MSIN provides the subscriber identity. Thus, only the MSIN portion of the IMSI typically needs to be encrypted. The MNC and MCC portions of the IMSI provide routing information, used by the serving network to route to the correct home network. When the MSIN of a SUPI is encrypted, it is referred to as Subscription Concealed Identifier (SUCI). Another example of a SUPI uses a Network Access Identifier (NAI). NAI is typically used for loT communication. The access point 104 is illustratively part of a radio access network or RAN of the communication system 100. Such a radio access network may comprise, for example, a 5G System having a plurality of base stations. Components of a radio access network may, more generally, be considered “radio access entities.” Further, the access point 104 in this illustrative embodiment is operatively coupled to an Access and Mobility Management Function (AMF / SEAF) 106. In a 5G network, the AMF / SEAF supports, inter alia, mobility management (MM) and security anchor (SEAF) functions. AMF / SEAF 106 in this illustrative embodiment is operatively coupled to (e.g., uses the services of) other network functions 108. As shown, some of these other network functions 108 include, but are not limited to, an Authentication Server Function (AUSF) and a Unified Data Management (UDM) function. These listed network function examples are typically implemented in the home network of the UE subscriber, further explained below. Note that, in a 5GC network, the 4G function of the HSS (home subscriber server) is split into the AUSF, UDM, and a Unified Data Repository (UDR, not expressly shown) functions. Typically, AUSF authenticates UEs and provides any needed cryptographic keys, while UDR stores the user data and UDM manages the user data. Other network functions 108 may include network functions that can act as service producers (NFp) and / or service consumers (NFc). Note that any network function can be a service producer for one service and a service consumer for another service. Further, when the service being provided includes data, the data-providing NFp is referred to as a data producer, while the data-requesting NFc is referred to as a data consumer. A data producer may also be an NF that generates data by modifying or otherwise processing data produced by another NF. Note thatNFs may, more generally, be considered “network entities.” Note that a UE, such as UE 102, is typically subscribed to what is referred to as a Home Public Land Mobile Network (HPLMN) in which some or all of the functions 106 and 108 reside. Alternatively the UE, such as UE 102, may receive services from an NPN where these functions may reside. The HPLMN is also referred to as the Home Environment (HE). If the UE is roaming (not in the HPLMN), it is typically connected with a Visited Public Land Mobile Network (VPLMN) also referred to as a visited network, while the network that is currently serving the UE is also referred to as a serving network. In the roaming case, some of the network functions 106 and 108 can reside in the VPLMN, in which case, functions in the VPLMN communicate with functions in the HPLMN as needed. However, in a non-roaming scenario, mobility management functions 106 and the other network functions 108 reside in the same communication network, i.e. HPLMN. Embodiments described herein, unless otherwise specified, are not necessarily limited by which functions reside in which PLMN (i.e., HPLMN or VPLMN). The access point 104 is also operatively coupled (via one or more of functions 106 and / or 108) to a Session Management Function (SMF) 110, which is operatively coupled to a User Plane Function (UPF) 112. UPF 112 is operatively coupled to a Packet Data Network, e.g., Internet 114. Note that the thicker solid lines in this figure denote a user plane (UP) of the communication network, as compared to the thinner solid lines that denote a control plane (CP) of the communication network. It is to be appreciated that network (e.g., Internet) 114 in FIG. 1 may additionally or alternatively represent other network infrastructures including, but not limited to, cloud computing infrastructure and / or edge computing infrastructure. Further typical operations and functions of such network elements are not described here since they are not the focus of the illustrative embodiments and may be found in appropriate 3GPP 5G documentation. Note that functions shown in 106, 108, 110 and 112 are examples of network functions (NFs). It is to be appreciated that this particular arrangement of system elements is an example only, and other types and arrangements of additional or alternative elements can be used to implement a communication system in other embodiments. For example, in other embodiments, the communication system 100 may comprise other elements / functions not expressly shown herein. Accordingly, the FIG. 1 arrangement is just one example configuration of a wireless cellular system, and numerous alternative configurations of system elements may be used. For example, although only single elements / functions are shown in the FIG. 1 embodiment, this is for simplicity and clarity of description only. A given alternative embodiment may of course include larger numbers of such system elements, as well as additional or alternative elements of a type commonly associated with conventional system implementations. It is also to be noted that while FIG. 1 illustrates system elements as singular functional blocks, the various subnetworks that make up the 5G network are partitioned into so-called network slices. Network slices (network partitions) are logical networks that provide specific network capabilities and network characteristics that can support a corresponding service type, optionally using network function virtualization (NFV) on a common physical infrastructure. With NFV, network slices are instantiated as needed for a given service, e.g., eMBB service, massive loT service, and mission-critical loT service. A network slice or function is thus instantiated when an instance of that network slice or function is created. In some embodiments, this involves installing or otherwise running the network slice or function on one or more host devices of the underlying physical infrastructure. UE 102 is configured to access one or more of these services via access point 104. FIG. 2 is a block diagram illustrating computing architectures for various participants in methodologies according to illustrative embodiments. More particularly, system 200 is shown comprising user equipment (UE) 202 and a plurality of entities 204-1, ...., 204-N. For example, in illustrative embodiments and with reference back to FIG. 1, UE 202 can represent UE 102, while entities 204-1, ..., 204-N can represent functions 106 and 108 (i.e., network entities), as well as access point 104 (i.e., radio access entity). It is to be appreciated that the UE 202 and entities 204-1, ...., 204-N are configured to interact to provide security management and other techniques described herein. The user equipment 202 comprises a processor 212 coupled to a memory 216 and interface circuitry 210. The processor 212 of the user equipment 202 includes a security management processing module 214 that may be implemented at least in part in the form of software executed by the processor. The security management processing module 214 performs security management described in conjunction with subsequent figures and otherwise herein. The memory 216 of the user equipment 202 includes a security management storage module 218 that stores data generated or otherwise used during security management operations. Each of the entities (individually or collectively referred to herein as 204) comprises a processor 222 (222-1, ..., 222-N) coupled to a memory 226 (226-1, ..., 226-N) and interface circuitry 220 (220-1, ..., 220-N). Each processor 222 of each entity 204 includes a security management processing module 224 (224-1, ..., 224-N) that may be implemented at least in part in the form of software executed by the processor 222. The security management processing module 224 performs security management operations described in conjunction with subsequent figures and otherwise herein. Each memory 226 of each entity 204 includes a security management storage module 228 (228-1, ..., 228-N) that stores data generated or otherwise used during security management operations. The processors 212 and 222 may comprise, for example, microprocessors such as central processing units (CPUs), application-specific integrated circuits (ASICs), digital signal processors (DSPs) or other types of processing devices, as well as portions or combinations of such elements. The memories 216 and 226 may be used to store one or more software programs that are executed by the respective processors 212 and 222 to implement at least a portion of the functionality described herein. For example, security management operations and other functionality as described in conjunction with subsequent figures and otherwise herein may be implemented in a straightforward manner using software code executed by processors 212 and 222. A given one of the memories 216 and 226 may therefore be viewed as an example of what is more generally referred to herein as a computer program product or still more generally as a processor-readable storage medium that has executable program code embodied therein. Other examples of processor-readable storage media may include disks or other types of magnetic or optical media, in any combination. Illustrative embodiments can include articles of manufacture comprising such computer program products or other processor-readable storage media. Further, the memories 216 and 226 may more particularly comprise, for example, electronic random-access memory (RAM) such as static RAM (SRAM), dynamic RAM (DRAM) or other types of volatile or non-volatile electronic memory. The latter may include, for example, non-volatile memories such as flash memory, magnetic RAM (MRAM), phasechange RAM (PC-RAM) or ferroelectric RAM (FRAM). The term “memory” as used herein is intended to be broadly construed, and may additionally or alternatively encompass, for example, a read-only memory (ROM), a disk-based memory, or other type of storage device, as well as portions or combinations of such devices. The interface circuitries 210 and 220 illustratively comprise transceivers or other communication hardware or firmware that allows the associated system elements to communicate with one another in the manner described herein. It is apparent from FIG. 2 that user equipment 202 and plurality of entities 204 are configured for communication with each other as security management participants via their respective interface circuitries 210 and 220. This communication involves each participant sending data to and / or receiving data from one or more of the other participants. The term “data” as used herein is intended to be construed broadly, so as to encompass any type of information that may be sent between participants including, but not limited to, identity data, key pairs, key indicators, tokens, secrets, security management messages, registration request / response messages and data, request / response messages, authentication request / response messages and data, metadata, control data, audio, video, multimedia, consent data, other messages, etc. It is to be appreciated that the particular arrangement of components shown in FIG. 2 is an example only, and numerous alternative configurations may be used in other embodiments. For example, any given network element / function and / or access point can be configured to incorporate additional or alternative components and to support other communication protocols. Other system elements such as access point 104, SMF 110, and UPF 112 may each be configured to include components such as a processor, memory and network interface. These elements need not be implemented on separate stand-alone processing platforms, but could instead, for example, represent different functional portions of a single common processing platform. More generally, FIG. 2 can be considered to represent processing devices configured to provide respective security management functionalities and operatively coupled to one another in a communication system. As mentioned above, the 3GPP TS 23.501 defines the 5GC network architecture as service-based, e.g., Service-Based Architecture (SBA). It is realized herein that in deploying different NFs, there can be many situations where an NF may need to interact with an entity external to the SBA-based 5GC network (e.g., including the corresponding PLMN(s), e.g., HPLMN and VPLMN). Thus, the term “internal” as used herein illustratively refers to operations and / or communications within the SBA-based 5GC network (e.g., SBA-based interfaces) and the term “external” illustratively refers to operations and / or communications outside the SBA-based 5GC network (non-SBA interfaces). Given the above general description of some features of a 5GC network, problems with existing security approaches in the context of security algorithm selection, and solutions proposed in accordance with illustrative embodiments, will now be described herein below. It is realized herein that communication networks should be adapted for Access Stratum (AS) and Non-Access Stratum (NAS) procedures with respect to enhanced key length security algorithms. By way of example, it is realized herein that existing AS and NAS procedures should be extended to support 256-bit algorithms in a seamless manner. However, it is further realized herein that current 128-bit algorithms should still be supported while the roll-out of 256-bit algorithms is completed on the network side as well as on the UE side. The global rollout, though, may take several years to complete. During the roll-out phase, both key length algorithms should co-exist. Illustrative embodiments address the above and other security algorithm support goals by expanding UE security capability information element (IE) data to indicate the support for longer key length algorithms, e.g., 256-bit algorithms, to the communication network. Then, to ensure the highest security in the choice of algorithms, a rule is introduced on the network side and the UE side to select the most secure algorithm, e.g., one of the 256-bit algorithms, during the negotiation, if the UE indicates support for 256-bit algorithms. FIG. 3 illustrates a procedure 300 for security algorithm selection according to an illustrative embodiment. As shown, procedure 300 involves a UE 302, a radio access network (RAN) 304, an AMF 306, and a home network (HN) 308. In step 1, UE 302 establishes a Radio Resource Control (RRC) connection with RAN 304. RRC is a layer within the 5G New Radio (NR) protocol stack that operates in the control plane between UE 302 and in RAN 304 (e.g., gNB). In step 2, UE 302 sends an initial NAS message (e.g., registration request message) to the communication network, i.e., AMF 306, with indication of UE security capabilities including support for 256-bit integrity protection algorithms and 256-bit encryption algorithms. In step 3, a further authentication and key agreement (AKA) challenge among UE 302, AMF 306, and HN 308 is performed similar to the AKA challenge described in the abovereferenced TS 33.501. In step 4 (i.e., NAS security mode command (SMC) procedure), after successful authentication of UE 302, AMF 306 selects and starts the integrity protection using a 256-bit algorithm, i.e., sub-step 4a. AMF sends the NAS security mode command, in sub-step 4b, with replayed UE security capabilities received initially from UE (in step 2) and also the selected 256-bit integrity algorithm and 256-bit encryption algorithm towards UE 302. In sub-step 4c, once the MAC is verified at UE 302, a NAS security mode complete message is sent to AMF 306 and the message is both integrity-protected and ciphered using the respective 256-bit algorithms selected by AMF 306. In step 5, the AS SMC procedure is performed. The AS SMC procedure is for RRC and UP security algorithm negotiation and RRC security activation. When the AS security context is to be established in the RAN 304 (i.e., gNB), in sub-step 5a, AMF 306 sends the complete UE 5G security capabilities to RAN 304 (i.e., all bits for every capability defined in the above-referenced TS 24.501 and received in NAS signaling). Extended IE security capabilities with 256-bit integrity protection algorithm and ciphering algorithm are received in RAN 304. RAN 304 chooses the 256-bit ciphering algorithm which has the highest priority from its configured list and is also present in the UE 5G security capabilities. The gNB also chooses the 256-bit integrity algorithm which has the highest priority from its configured list and is also present in the UE 5G security capabilities (sub-step 5b). The chosen algorithms are indicated by RAN 304 to UE 302 in the AS SMC message (sub-step 5c) and this message is integrity protected. Once the message authentication code (MAC) is verified at UE 302, in sub-step 5d, AS security mode complete message is sent to RAN 304 and the message is both integrity-protected and ciphered using the selected 256-bit algorithms. Note that AS SMC negotiation between UE 302 and RAN 304 (i.e., gNB) may result in increased MAC-I based on the UE security capabilities. FIGS. 4 and 5 respectively show NAS information element data 400 and 500 (i.e., showing extended information element (IE) / information element identifiers (IEI) adapted from the above-referenced TS 24.501) that indicate that UE 302 is configured to support 256-bit integrity protection algorithms and 256-bit encryption algorithms, i.e., UE security capabilities. Note that in FIG. 4, octet 3 to 6 is mainly for 32-bit MAC generation or the current configuration of MAC generation. Octet 7 to 10 is now extended with 256-bit algorithms and 64-bit MAC generation support, which will be described herein in further illustrative embodiments. Furthermore, FIGS. 6A through 6C illustrate 5GNAS security algorithm information element data (IE / IEI data 600, 610, and 620, respectively) indicating communication network security capabilities including support for 256-bit integrity protection algorithms and 256-bit encryption algorithms according to an illustrative embodiment. With respect to the impact of security capability extension in the AS context (e.g., the above-referenced TS 38.331), illustrative embodiments provide the following approach. The IE SecurityAlgorithmConfig is used to configure the AS integrity-protection algorithm and the AS ciphering algorithm for Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs) as follows: SecurityAlgorithmConfig information element - ASN1 START - TAG-SECURITYALGORITHMCONFIG-START Security AlgorithmConfig ::= SEQUENCE { cipheringAlgorithm CipheringAlgorithm, integrityProtAlgorithm IntegrityProtAlgorithm OPTIONAL, — Need R } IntegrityProtAlgorithm ::= ENUMERATED { niaO, nial, nia2, nia3, nia4, nia5,nia6, nia7, nia8,nia9,sparel, ...} CipheringAlgorithm ::= ENUMERATED {neaO, neal, nea2, nea3, nea4, nea5,nea6, nea7, nea8,nea9, sparel, ...} - TAG-SECURITYALGORITHMCONFIG-STOP - ASN1STOP Note: nia4, nia5 and nia6 corresponds to 256 integrity bit algorithm with existing MAC-I generation (example: 32-bit MAC-I). Note: nea4, nea5 and nea6 corresponds to 256 encryption bit algorithm with existing MAC-I generation (example 32-bit MAC-I). Note: nia7, nia8 and nia9 corresponds to 256 integrity bit algorithm with new extension of MAC-I generation (example: 64-bit MAC-I). Note: nea7, nea8 and nea9 corresponds to 256 encryption bit algorithm with new extension of MAC-I generation (example 64-bit MAC-I). With respect to the impact of security capability extension in the SA3 context (e.g., the above-referenced TS 33.501), illustrative embodiments provide the following approach. Each encryption (ciphering) algorithm is assigned a 4-bit identifier. The following values for ciphering algorithms are defined: "00002" NEAO Null ciphering algorithm. "00012" 128-NEA1 128-bit SNOW 3Gbased algorithm. "00102" 128-NEA2 128-bit AES based algorithm; and "00112" 128-NEA3 128-bit ZUC based algorithm. "01002" 256-NEA1 256-bit SNOW 3Gbased algorithm. "01012" 256-NEA2 256-bit AES based algorithm; and "01102" 256-NEA3 256-bitZUC based algorithm. 128-NEA1 is based on SNOW 3G (see TS 35.215). 128-NEA2 is based on 128-bit AES in CTR mode. 128-NEA3 is based on 128-bit ZUC (see TS 35.221). 256-NEA1 is based on SNOW 256-bit algo (see TS 35.215 to be adapted). 256-NEA2 is based on 256-bit AES in CTR mode. 256-NEA3 is based on 256-bit ZUC (see TS 35.221 to be adapted). Each integrity algorithm used for 5G will be assigned a 4-bit identifier. The following values for integrity algorithms are defined: "00002" NIA0 Null Integrity Protection algorithm. "00012" 128-NIA1 128-bit SNOW 3G based algorithm. "00102" 128-NIA2 128-bit AES based algorithm; and "00112" 128-NIA3 128-bit ZUC based algorithm. "01002" 256-NIA1 256-bit SNOW 3G based algorithm. "01012" 256-NIA2 256-bit AES based algorithm; and "01102" 256-NIA3 256-bit ZUC based algorithm. 128-NIA1 is based on SNOW 3G (see TS 35.215). 128-NIA2 is based on 128-bit AES in CMAC mode. 128-NIA3 is based on 128-bit ZUC (see TS 35.221). 256-NIA1 is based on SNOW 256-bit algo (see TS 35.215 to be adapted). 256-NIA2 is based on 256-bit AES in CMAC mode. 256-NIA3 is based on 256-bit ZUC (see TS 35.221 to be adapted). Referring now to FIG. 7, a network-side key derivation 700 for a selected 256-bit security algorithm I illustrated, while FIG. 8 illustrates a user equipment-side key derivation 800 for a selected 256-bit security algorithm according to an illustrative embodiment. Further, for an NAS integrity algorithm, it is to be appreciated that the input parameters to the integrity algorithm are a 256-bit integrity key named KEY, a 32-bit COUNT, a 5-bit bearer identity called BEARER, the 1 -bit direction of the transmission, i.e., DIRECTION, and the message itself, i.e., MESSAGE. In an illustrative embodiment, the DIRECTION bit is 0 for uplink and 1 for downlink. The bit length of the MESSAGE is LENGTH. FIG. 9 illustrates a process 900 using the integrity algorithm NIA to authenticate the integrity of messages. More particularly, process 900 illustrates derivation of MAC-I / NAS-MAC (or XMAC-I / XNAS-MAC). That is, based on these input parameters, the sender computes a 32-bit or 64-bit message authentication code (MAC-I / NAS-MAC) using the integrity algorithm NIA. The message authentication code is then appended to the message when sent. For integrity protection algorithms, the receiver computes the expected message authentication code (XMAC-I / XNAS-MAC) on the message received in the same way as the sender computed its message authentication code on the message sent and verifies the data integrity of the message by comparing it to the received message authentication code, i.e., MAC-I / NAS-MAC. With respect to NAS input parameters to the integrity algorithm, the input parameters to the NAS 256-bit integrity algorithms are as follows: The KEY input shall be equal to the KNASint key. The BEARER input shall be equal to the NAS connection identifier. The DIRECTION bit shall be set to 0 for uplink and 1 for downlink. The COUNT input shall be constructed as follows: COUNT := 0x00 || NAS COUNT where NAS COUNT is the 24-bit NAS UL COUNT or the 24-bit NAS DL COUNT value, depending on the direction, that is associated to the current NAS connection identified by the value used to form the BEARER input. ANAS COUNT shall be constructed as follows: NAS COUNT := NAS OVERFLOW || NAS SQN where: NAS OVERFLOW is a 16-bit value which is incremented each time the NAS SQN is incremented from the maximum value, and NAS SQN is the 8-bit sequence number carried within each NAS message. Further, for the NAS ciphering (e.g., encryption / confidentiality) algorithm, it is to be appreciated that the input parameters to the algorithm are a 256-bit cipher key named KEY, a 32-bit COUNT, a 5-bit bearer identity BEARER, the 1-bit direction of the transmission i.e., DIRECTION, and the length of the keystream required i.e., LENGTH. The DIRECTION bit is 0 for uplink and 1 for downlink in one or more illustrative embodiments. FIG. 10 illustrates a process 1000 using a ciphering algorithm NE A to encrypt plaintext by applying a key stream using a bit per bit binary addition of the plaintext and the key stream. The plaintext may be recovered by generating the same keystream using the same input parameters and applying a bit per bit binary addition with the ciphertext. Based on the input parameters, the algorithm in process 1000 generates the output keystream block KEYSTREAM which is used to encrypt the input plaintext block PLAINTEXT to produce the output ciphertext block CIPHERTEXT. The input parameter LENGTH affects only the length of the KEYSTREAM BLOCK, not the actual bits in it. With respect to NAS input parameters, the input parameters for the NAS 256-bit ciphering algorithms are the same as the ones used for NAS integrity protection as described in the above-referenced TS 33.501, with the exception that a different key, KNASenc, is used as KEY, and there is an additional input parameter, namely the length of the key stream to be generated by the encryption algorithms. The use and mode of operation of the 256-bit ciphering algorithms are further specified in the above-referenced TS 33.501. Note that in the context of the above-referenced TS 33.501, a message is considered ciphered also when the NULL encryption algorithm NEA0 is applied. With respect to RRC integrity algorithm and the confidentiality algorithm, RRC integrity protection is provided by the Packet Data Convergence Protocol (PDCP) layer between UE 302 and RAN 304 (i.e., gNB) and no layers below PDCP are integrity protected. Replay protection is activated when integrity protection is activated (except for when the selected integrity protection algorithm is NIA0). Replay protection ensures that the receiver accepts each particular incoming PDCP COUNT value only once using the same AS security context. The use and mode of operation of the 256-NIA algorithms are specified in the abovereferenced TS 33.501. The input parameters to the 256-bit NIA algorithms as described in the abovereferenced TS 33.501 are the RRC message as MESSAGE, an 256-bit integrity key KRRCint as KEY, a 5-bit bearer identity BEARER which value is assigned as specified by the abovereferenced TS 38.323, the 1-bit direction of transmission DIRECTION and a bearer specific direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. The RRC integrity checks are performed both in the ME of UE 302 and RAN 304 (i.e., gNB). In case a failed integrity check (i.e., faulty or missing MAC-I) is detected after the start of integrity protection, the concerned message is discarded. This can happen on the gNB side or on the ME side. UE 302 may trigger a recovery procedure as specified in the abovereferenced TS 38.331. Note that a failed integrity check does not always imply that the concerned message is silently discarded. RRC confidentiality protection is provided by the PDCP layer between UE 302 and RAN 304 (i.e., gNB). The use and mode of operation of the 256-NEA algorithms are specified in the above-referenced TS 33.501. The input parameters to the 256-bit NEA algorithms are a 256-bit cipher Key KRRCenc as KEY, a 5-bit bearer identity BEARER which corresponds to the radio bearer identity, the 1-bit direction of transmission DIRECTION, the length of the keystream required LENGTH and a bearer specific direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. With respect to the UP (user plane) integrity algorithm and confidentiality algorithm, the use and mode of operation of the 256-bit NIA algorithms are specified in the abovereferenced TS 33.501. The input parameters to the 256-bit NIA algorithms are the message packet, a 256-bit integrity key Kupint as KEY, a 5-bit bearer identity BEARER value of which is assigned as specified by the above-referenced TS 38.323, the 1-bit direction of transmission DIRECTION, and a bearer specific, and direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. If RAN 304 (i.e., gNB) or UE 302 receives a PDCP PDU which fails integrity check with a faulty or missing MAC-I after the start of integrity protection, the PDU is discarded. For UP integrity mechanisms between UE 302 and an ng-eNB (RAN 304), if UE 302 supports E-UTRA connected to 5GC, UE 302 indicates support of integrity protection by setting the EIA7 algorithm bit in 5G UE Security Capability IE (see the above-referenced TS 24.501) to indicate that UE 302 supports user plane integrity protection with an ng-eNB. While a gNB is the 5G radio base station that connects 5G NR devices to the 5GC using the NR radio interface, an ng-eNB is an upgraded version of a 4G LTE radio base station that connects 4G LTE devices to the 5GC network using the LTE radio interface. If the 256-NIA algorithm is signalled by the ng-eNB to UE 302, the above-referenced TS 33.501 applies. However, if the 256-EIA algorithm is signalled by the ng-eNB to UE 302, the following applies. The use and mode of operation of the 256-EIA algorithms are specified in the above-referenced TS 33.501. The input parameters to the 256-bit EIA algorithms as described in the above-referenced TS 33.401 are the message packet, a 256-bit integrity key KUPint as KEY, a 5-bit bearer identity BEARER value of which is assigned as specified by the above-referenced TS 38.323, the 1-bit direction of transmission DIRECTION, and a bearer specific, time and direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. Note that the ng-eNB decides whether to signal 256-NIA or 256-EIA algorithm. If the ng-eNB or UE 302 receives a PDCP PDU which fails integrity check with a faulty or missing MAC-I after the start of integrity protection, the PDU is discarded. UE 302 and the ng-eNB (or the ng-eNB acting as the MN) derive UP integrity key as specified in the abovereferenced TS 33.401 with the K6nb set to KgNB. The PDCP protocol, as specified in the above-referenced TS 38.323 between UE 302 and RAN 304 is responsible for UP data confidentiality protection. The use and mode of operation of the 256-bit NEA algorithms are specified in the above-referenced TS 33.501. The input parameters to the 256-bit NEA algorithms are the message packet, an 256-bit cipher key Kupenc as KEY, a 5-bit bearer identity BEARER which value is assigned as specified by the above-referenced TS 38.323, the 1-bit direction of transmission DIRECTION, the length of the keystream required LENGTH and a bearer specific, and direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. For N2 handover, (target) AMF 306 calculates a 64-bit NAS MAC over the parameters included in the NAS container (NASC) using the KNASint key. The input parameters to the NAS 256-bit integrity algorithms as described in the above-referenced TS 33.501 are set as follows when calculating NAS MAC. For step 3 of procedure 300 of FIG. 3, (target) AMF 306 constructs a mapped 5G security context from the EPS security context received from the source MME (mobility management entity, not expressly shown). AMF 306 derives a mapped Kamf key from the received Kasme and the next hop (NH) value in the Evolved Packet System (EPS) security context received from the source MME. If AMF 306 receives the UE 5G security capabilities, then AMF 306 selects the 5GNAS security algorithms (to be used in AMF 306 for encryption and integrity protection) which have the highest priority from its configured list. If AMF 306 does not receive the UE 5G security capabilities from the source MME, then AMF 306 assumes that the following default set of 5G security algorithms are supported by UE 302 (and sets the UE 5G security capabilities in the mapped 5GNAS security context according to this default set): (i) NEA0, 256-NEA1 and 256-NEA2 for NAS signaling ciphering, RRC signaling ciphering and UP ciphering; and (ii) 256-NIA1 and 256-NIA2 for NAS signaling integrity protection, RRC signaling integrity protection and UP integrity protection. In accordance with additional illustrative embodiments, an increased MAC length is introduced to indicate this as an additional field in the AS SMC, as only AS MAC needs the extension. So, the UE capability IE contains algorithm information (extended to 256-bit algorithm). However, the algorithm selection and MAC length negotiation occurs via AS SMC. For example, FIG. 11 illustrates information element data 1100 for UE security capabilities according to such an illustrative extended MAC length embodiment. Further, FIG. 12 illustrates a procedure 1200 which is similar in steps 1 through 5 of procedure 300 of FIG. 3 with the exceptions that step 2 specifies the UE support for the extended MAC feature, and sub-step 5c of FIG. 3 becomes sub-step 5b of FIG. 12 with the extended MAC feature. Lastly, FIG. 13 illustrates a procedure 1300 for extended length message authentication code selection according to an illustrative embodiment. More particularly, steps 1 and 2 show the registration procedure and NAS SMC procedure, respectively. Step 3 denotes the AS SMC procedure wherein step 4 (sub-steps 4a through 4c) depicts the AS SMC exchange. More particularly, when RAN 304 (i.e., gNB) initiates the AS SMC procedure in legacy mode, UE 302 indicates the request for increased MAC length (sub-steps 4a and 4b) and RAN 304 acknowledges with a separate RRC procedure (part of sub-step 4c). As explained in detail herein, illustrative embodiments provide for security algorithm selection functionalities implemented within user equipment (e.g., UE), one or more network entities (e.g., an AMF), and one or more radio access entities (e.g., a RAN node such as a gNB). As such, from a UE perspective, an apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: (i) send a first message to a network entity of a communication network indicating a set of security algorithms supported by the apparatus, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; and (ii) receive a second message indicating at least one security algorithm from the set of security algorithms, wherein the at least one security algorithm is one having the longest key length supported by the communication network among the first key length and the at least a second key length. In a first security mode command context, the second message may be received from the network entity of the communication network. The first security mode command context may comprise a non-access stratum security command mode procedure. In a second security mode command context, the second message may be received from a radio access entity associated with the network entity of the communication network. The second security mode command context may comprise an access stratum security command mode procedure. In the second security mode command context, the first message may further indicate support by the apparatus for use of an extended length message authentication code. The set of security algorithms may comprise one or more integrity protection algorithms and one or more encryption algorithms, wherein the first key length comprises 128 bits and the second key length comprises 256 bits. Further, a method may comprise: (i) sending, from user equipment to a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; and (ii) receiving, at the user equipment, a second message indicating at least one security algorithm from the set of security algorithms, wherein the at least one security algorithm is one having the longest key length supported by the communication network among the first key length and the at least a second key length. In another embodiment, a non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to perform the above-mentioned method. Still from a UE perspective, an apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to coordinate with a radio access entity of a communication network to utilize an extended length message authentication code when performing an access stratum security mode command procedure. From a network entity perspective (e.g., AMF), an apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: (i) receive a first message from user equipment indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; (ii) select at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by a communication network to which the apparatus belongs among the first key length and the at least a second key length; and (iii) send a second message indicating the selected at least one security algorithm. In a first security mode command context, the second message may be sent by the apparatus to the user equipment. The first security mode command context may comprise a non-access stratum security command mode procedure. In a second security mode command context, the second message may be sent by the apparatus to a radio access entity associated with the apparatus. The second security mode command context may comprise an access stratum security command mode procedure. In the second security mode command context, the first message may further indicate support by the user equipment for use of an extended length message authentication code. The set of security algorithms may comprise one or more integrity protection algorithms and one or more encryption algorithms, and the first key length comprises 128 bits and the second key length comprises 256 bits. Further, a method may comprises: (i) receiving, from user equipment at a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; (ii) selecting, by the network entity, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by a communication network to which the network entity belongs among the first key length and the at least a second key length; and (iii) sending, from the network entity to the user equipment, a second message indicating the selected at least one security algorithm. In another embodiment, a non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to perform the above-mentioned method. From a radio access entity perspective (e.g., RAN node such as a gNB), an apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: (i) receive a first message from a network entity of a communication network indicating a set of security algorithms supported by user equipment with which the network entity has established a first security command mode context, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; (ii) select, for a second security command mode context, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by the communication network among the first key length and the at least a second key length; and (iii) send a second message to the user equipment indicating the selected at least one security algorithm. The first security mode command context may comprise a non-access stratum security command mode procedure. The second security mode command context may comprise an access stratum security command mode procedure. In the second security mode command context, the first message may further indicate support by the user equipment for use of an extended message authentication code. The set of security algorithms may comprise one or more integrity protection algorithms and one or more encryption algorithms, wherein the first key length comprises 128 bits and the second key length comprises 256 bits. Further, a method may comprise: (i) receiving, at a radio access entity from a network entity of a communication network, a first message indicating a set of security algorithms supported by user equipment with which the network entity has established a first security command mode context, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; (ii) selecting, by the radio access entity for a second security command mode context, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by the communication network among the first key length and the at least a second key length; and (iii) sending, from the radio access entity to the user equipment, a second message to the user equipment indicating the selected at least one security algorithm. In another embodiment, a non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to perform the above-mentioned method. Still from a RAN perspective, an apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to coordinate with user equipment to utilize an extended length message authentication code when performing an access stratum security mode command procedure. As used herein, it is to be understood that the term “communication network” in some embodiments can comprise two or more separate communication networks. Further, the particular processing operations and other system functionality described in conjunction with the diagrams described herein are presented by way of illustrative example only and should not 5 be construed as limiting the scope of the disclosure in any way. Alternative embodiments can use other types of processing operations and messaging protocols. For example, the ordering of the steps may be varied in other embodiments, or certain steps may be performed at least in part concurrently with one another rather than serially. Also, one or more of the steps may be repeated periodically, or multiple instances of the methods can be performed in parallel with 10 one another. It should again be emphasized that the various embodiments described herein are presented by way of illustrative example only and should not be construed as limiting the scope of the claims. For example, alternative embodiments can utilize different communication system configurations, user equipment configurations, base station configurations, 15 provisioning and usage processes, messaging protocols and message formats than those described above in the context of the illustrative embodiments. These and numerous other alternative embodiments within the scope of the appended claims will be readily apparent to those skilled in the art.

Claims

1. An apparatus comprising:means for sending a first message to a network entity of a communication network indicating a set of security algorithms supported by the apparatus, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; andmeans for receiving a second message indicating at least one security algorithm from the set of security algorithms, wherein the at least one security algorithm is one having the longest key length supported by the communication network among the first key length and the at least a second key length.

2. The apparatus of claim 1, wherein, in a first security mode command context, the second message is received from the network entity of the communication network.

3. The apparatus of claim 2, wherein the first security mode command context comprises a non-access stratum security command mode procedure.

4. The apparatus of claim 1, wherein, in a second security mode command context, the second message is received from a radio access entity associated with the network entity of the communication network.

5. The apparatus of claim 4, wherein the second security mode command context comprises an access stratum security command mode procedure.

6. The apparatus of claim 4, wherein, in the second security mode command context, the first message further indicates support by the apparatus for use of an extended length message authentication code.

7. The apparatus of claim 1, wherein the set of security algorithms comprises one or more integrity protection algorithms and one or more encryption algorithms.

8. A method comprising:sending, from user equipment to a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length; andreceiving, at the user equipment, a second message indicating at least one security algorithm from the set of security algorithms, wherein the at least one security algorithm is one having the longest key length supported by the communication network among the first key length and the at least a second key length.

9. An apparatus comprising:means for coordinating with a radio access entity of a communication network to utilize an extended length message authentication code when performing an access stratum security mode command procedure; andmeans for utilizing the extended length message authentication code.

10. An apparatus comprising:means for receiving a first message from user equipment indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length;means for selecting at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by a communication network to which the apparatus belongs among the first key length and the at least a second key length; andmeans for sending a second message indicating the selected at least one security algorithm.

11. The apparatus of claim 10, wherein, in a first security mode command context, the second message is sent by the apparatus to the user equipment.

12. The apparatus of claim 11, wherein the first security mode command context comprises a non-access stratum security command mode procedure.

13. The apparatus of claim 10, wherein, in a second security mode command context, the second message is sent by the apparatus to a radio access entity associated with the apparatus.

14. The apparatus of claim 13, wherein the second security mode command context comprises an access stratum security command mode procedure.

15. The apparatus of claim 13, wherein, in the second security mode command context, the first message further indicates support by the user equipment for use of an extended length message authentication code.

16. The apparatus of claim 10, wherein the set of security algorithms comprises one or more integrity protection algorithms and one or more encryption algorithms.

17. A method comprising:receiving, from user equipment at a network entity of a communication network, a first message indicating a set of security algorithms supported by the user equipment, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length;selecting, by the network entity, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by a communication network to which the network entity belongs among the first key length and the at least a second key length; andsending, from the network entity to the user equipment, a second message indicating the selected at least one security algorithm.

18. An apparatus comprising:means for receiving a first message from a network entity of a communication network indicating a set of security algorithms supported by user equipment with which the networkentity has established a first security command mode context, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length;means for selecting, for a second security command mode context, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by the communication network among the first key length and the at least a second key length; andmeans for sending a second message to the user equipment indicating the selected at least one security algorithm.

19. The apparatus of claim 18, wherein the first security mode command context comprises a non-access stratum security command mode procedure.

20. The apparatus of claim 18, wherein the second security mode command context comprises an access stratum security command mode procedure.

21. The apparatus of claim 18, wherein, in the second security mode command context, the first message further indicates support by the user equipment for use of an extended message authentication code.

22. The apparatus of claim 18, wherein the set of security algorithms comprises one or more integrity protection algorithms and one or more encryption algorithms.

23. The apparatus of claim 18, wherein the first key length comprises 128 bits and the second key length comprises 256 bits.

24. A method comprising:receiving, at a radio access entity from a network entity of a communication network, a first message indicating a set of security algorithms supported by user equipment with which the network entity has established a first security command mode context, wherein a first subset of the set of security algorithms is configured with a first key length and at least a second subset of the set of security algorithms is configured with at least a second key length;selecting, by the radio access entity for a second security command mode context, at least one security algorithm from the set of security algorithms, wherein the selected at least one security algorithm is one with the longest key length supported by the communication network among the first key length and the at least a second key length; and5          sending, from the radio access entity to the user equipment, a second message to theuser equipment indicating the selected at least one security algorithm.

25. An apparatus comprising:means for coordinating with user equipment to utilize an extended length message 10 authentication code when performing an access stratum security mode command procedure; andmeans for utilizing the extended length message authentication code.

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