Communication device and method therein for facilitating macsec communication

Abstract

The present disclosure provides a method (200) in a first communication device. The method (200) comprises: in response to a media access control security (MACsec) becoming unavailable in a secure MACsec key agreement (MKA) session, sending (210) MKA teardown information to a second communication device, the MKA teardown information indicating that the first communication device will tear down the MKA session with the second communication device; and receiving (220) unencrypted data from the second communication device.

Description

Technical Field

[0001] This disclosure relates to communication technologies, and more specifically, to communication devices and methods for facilitating Media Access Control Security (MACsec) communications. Background Technology

[0002] Media Access Control Security (MACsec) is an industry-standard security technology that provides secure communication for virtually all types of services over Ethernet links. MACsec provides point-to-point (P2P) security over Ethernet links between directly connected nodes and can identify and prevent most security threats, including denial-of-service, intrusion, man-in-the-middle attacks, spoofing, passive eavesdropping, and replay attacks.

[0003] MACsec is defined in IEEE standard 802.1AE-2018 "Media AccessControl (MAC) Security", which is incorporated herein by reference in its entirety. This standard defines secure channels and security associations, among other things.

[0004] - Secure Channel: A Secure Channel (SC) is a one-way point-to-point channel. This SC can only be used to apply MACsec to inbound or outbound traffic. When MACsec is enabled, a typical connection association using the Secure Association Key (SAK) security mode includes two secure channels: one for inbound traffic and another for outbound traffic. Each channel has an 8-byte Secure Channel Identifier (SCI). The first six bytes match the MAC address of the outbound port through which the transmission is made. The remaining two bytes are a port identifier used to distinguish multiple channels originating from the same port.

[0005] -Security Associations: Communication on each secure channel as a series of transient sessions is called a Security Association (SA). Each secure channel includes up to two SAs. Generally, a channel has one SA. However, if SA replacement is required, the channel must have two SAs. For example, when rotating a key, two SAs are needed to switch from one key to another. An SA contains two key pieces of information necessary for encrypting and protecting the frame.

[0006] • Secure Associated Key (SAK): An encryption key derived from a pre-shared key.

[0007] • Packet Number (PN) associated with the counter: The PN is used for encryption, authentication, and replay protection during transmission. At the transmitting end of the channel, the counter records the next PN, while at the receiving end, the SA keeps track of the next expected PN.

[0008] The IEEE standard 802.1X-2020 "Port Based Network Access Control" (which is incorporated herein by reference in its entirety) defines the MACsec Key Agreement (MKA) protocol. The MKA protocol allows Port Access Entities (PAEs), each associated with a port that is an authenticated member of a Secure Connection Association (CA) or a potential CA, to discover other PAEs attached to the same Local Area Network (LAN), confirm that they possess a Connection Association Key (CAK) to prove past mutual authentication, negotiate a Secret Key (SAK) used by MACsec for symmetric shared key encryption, and ensure that data protected by MACsec has not been delayed.

[0009] MKA provides secure point-to-point transmission between members of the same CA, suitable for transmitting constant information or information refreshed or acknowledged by MKA applications utilizing the transmission. The CAK is used to authenticate each protocol data unit (MACsec key protocol data unit, or MKPDU) sent, thus providing proof of the CA member's transmission, and each station includes its own randomly selected identifier and message number in the MKPDU. By sending an MKPDU containing the identifiers of other participants and the most recent message number, each member proves that it currently possesses the CAK and is actively participating in the protocol, demonstrating the "activity" of the MKPDU and distinguishing it from an MKPDU that an attacker might have captured and later played or replayed (aimed at disrupting the protocol or influencing its outcome). When the data to be transmitted changes in accordance with Clause 9 of IEEE Standard 802.1X-2020, and in accordance with the PAE Control Port (CP) state machine (setting the state machine variable newInfo, as specified in Clause 12 of IEEE Standard 802.1X-2020), the MKPDU transmits at fixed intervals of MKA Hello time or MKA bounded Hello time (if bounded reception delay is to be guaranteed). Summary of the Invention

[0010] According to Clause 9.14 of IEEE Standard 802.1X-2020, MKA participants should be removed for any of the following reasons:

[0011] h) The CAK lifetime (if specified) has expired.

[0012] i) CAK originates from the Extensible Authentication Protocol (EAP) exchange, but failed to identify active peers with acceptable MACsec capabilities during the MKA lifetime (see Table 9-3 of IEEE Standard 802.1X-2020, which summarizes the timer usage and timeout values ​​for each MKA participant).

[0013] MKA participants may be removed for any of the following reasons:

[0014] j) The last key server used to distribute keys using that CAK is no longer in the participant's active peer list, but (as identified by its SCI) in the active peer list of another participant using the same public port.

[0015] k) Otherwise, the number of participants will exceed the number that the system can support.

[0016] The MKA lifetime is defined as 6 seconds. In most implementations, the lifetime is a configurable value ranging from 6 to 18 seconds. The MKA protocol maintains the participant's activity state based on the configured lifetime. If a participant does not receive any MKA packets from its peer within the lifetime, the participant can remove the established secure session.

[0017] MACsec supports a "should be secure" policy, which allows unencrypted traffic even when the MKA session is insecure. During MKA negotiation, communication devices (e.g., routers) attempt to establish an MKA session.

[0018] • If an MKA session is not established, the service is sent in plaintext without MACsec encryption and decryption.

[0019] • If an MKA session is successfully established, the service will send data using MACsec encryption and decryption.

[0020] Figure 1A and Figure 1B Each illustrates an exemplary scenario of P2P MACsec communication between router A and router B. Initially, as... Figure 1A As shown, after successful MKA negotiation, services are transmitted between router A and router B using MACsec encryption and decryption. Then, as... Figure 1B As shown, MACsec is disabled at router B, and router B stops sending MKAs to router A. According to the "should be secure" policy, router B begins sending unencrypted traffic to router A. At router A, the MKA session is maintained until its time-to-live expires. During the period after MACsec is disabled at router B and before its time-to-live expires at router A, router A still sends encrypted traffic to router B, but router B, due to its disabled MACsec, may be unable to decrypt the traffic. On the other hand, during this period, router A cannot decrypt traffic from router B because the traffic is effectively unencrypted. This will result in service interruption.

[0021] The purpose of this disclosure is to provide communication devices and methods therein that can solve or mitigate the aforementioned problems.

[0022] According to a first aspect of this disclosure, a method is provided in a first communication device. The method includes: in response to MACsec becoming unavailable in a secure MKA session, sending an MKA teardown message to a second communication device, the MKA teardown message instructing the first communication device to tear down the MKA session with the second communication device. The method further includes: receiving unencrypted data from the second communication device.

[0023] In this embodiment, the MKA removal information can be carried in the SAK USE parameter set or the removal parameter set in the MKPDU.

[0024] In an embodiment, the teardown parameter set may include an Advanced Encryption Standard (AES) key wrapper for the SAK associated with the MKA session.

[0025] In an embodiment, the method may further include: dismantling the MKA session and sending unencrypted data to a second communication device.

[0026] In an embodiment, the operation of dismantling an MKA session may include: deleting the MKA participants associated with the first communication device and the second communication device respectively, and deleting the SAK associated with the MKA session.

[0027] In an embodiment, MACsec becoming unavailable may include MACsec being disabled at the first communication device.

[0028] According to a second aspect of the invention, a method is provided in a second communication device. The method includes: receiving MKA teardown information from a first communication device, the MKA teardown information instructing the first communication device to tear down its MKA session with the second communication device. The method further includes sending unencrypted data to the first communication device.

[0029] In this embodiment, the MKA removal information can be carried in the SAK USE parameter set or the removal parameter set in the MKPDU.

[0030] In an embodiment, the teardown parameter set may include an AES key wrapper for the SAK associated with the MKA session.

[0031] In an embodiment, the method may further include: verifying MKA teardown information by wrapping an AES key based on SAK. Unencrypted data may be sent in response to successful verification of the MKA teardown information.

[0032] In one embodiment, the first communication device may act as a key server, and the second communication device may act as a client. The method may also include dismantling the MKA session in response to MKA teardown information.

[0033] In this embodiment, the first communication device may act as a client, and the second communication device may act as a key server. The method may further include: dismantling the MKA session in response to MKA teardown information when no other active clients exist in the MKA session; or deleting the MKA participants associated with the first and second communication devices respectively in response to MKA teardown information when at least one other active client exists in the MKA session.

[0034] In an embodiment, the operation of dismantling an MKA session may include: deleting the MKA participants associated with the first communication device and the second communication device respectively, and deleting the SAK associated with the MKA session.

[0035] In an embodiment, the method may further include: receiving unencrypted data from a first communication device after receiving MKA teardown information.

[0036] According to a third aspect of this disclosure, a first communication device is provided. The first communication device includes a communication interface, a processor, and a memory. The memory contains instructions executable by the processor, thereby enabling the first communication device to perform the method according to the first aspect described above.

[0037] According to a fourth aspect of this disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer-readable instructions stored thereon. When executed by a processor of a first communication device, the computer-readable instructions configure the first communication device to perform the method according to the first aspect described above.

[0038] According to a fifth aspect of this disclosure, a second communication device is provided. The second communication device includes a communication interface, a processor, and a memory. The memory contains instructions executable by the processor, thereby enabling the second communication device to perform the method according to the second aspect described above.

[0039] According to a sixth aspect of this disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer-readable instructions stored thereon. When executed by a processor of a second communication device, the computer-readable instructions configure the second communication device to perform the method according to the second aspect described above.

[0040] Through embodiments of this disclosure, when MACsec becomes unavailable at the communication device in a secure MKA session, the communication device can send an MKA teardown message to its peer device, instructing the communication device to tear down the MKA session with the peer device. In this case, the MKA session between the two devices can be torn down without waiting for the MKA's lifetime to expire. Therefore, unencrypted services can be transmitted between the two devices according to this security policy, and service interruptions due to inconsistencies in the MKA session states of the two devices can be avoided. Attached Figure Description

[0041] The above and other objects, features and advantages will become more apparent from the following description of embodiments with reference to the accompanying drawings, in which:

[0042] Figure 1A and Figure 1B These are schematic diagrams illustrating exemplary scenarios of P2P MACsec communication;

[0043] Figure 2 This is a flowchart illustrating a method in a first communication device according to an embodiment of the present disclosure;

[0044] Figure 3 This is a schematic diagram illustrating the MKPDU format;

[0045] Figure 4 This is a schematic diagram illustrating the format of the SAK USE parameter set according to an embodiment of the present disclosure;

[0046] Figure 5 This is a schematic diagram illustrating the format of a set of demolition parameters according to an embodiment of the present disclosure;

[0047] Figure 6 This is a flowchart illustrating a method in a second communication device according to an embodiment of the present disclosure;

[0048] Figure 7 This is a sequence diagram illustrating an example of the MKA session teardown process;

[0049] Figure 8 This is a block diagram illustrating a first communication device according to an embodiment of the present disclosure; and

[0050] Figure 9 This is a block diagram illustrating a second communication device according to an embodiment of the present disclosure. Detailed Implementation

[0051] References to "embodiment," "example," "exemplary embodiment," etc., in this specification indicate that the described embodiments may include specific features, structures, or characteristics, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Additionally, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be assumed that implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) is within the knowledge of those skilled in the art.

[0052] It should be understood that although the terms “first” and “second” may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish elements from one another. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms.

[0053] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context clearly indicates otherwise. It will be further understood that, when used herein, the words “comprising,” “having,” and “including” indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0054] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0055] Figure 2 This is a flowchart illustrating a method 200 according to an embodiment of the present disclosure. Method 200 can be performed by a first communication device, which can be, for example, a router or any suitable device supporting the MKA protocol. The first communication device can act as a key server or a client.

[0056] At box 210, in response to MACsec becoming unavailable in a secure MKA session, the first communication device sends an MKA teardown message to the second communication device, instructing the first communication device to terminate its MKA session with the second communication device. This can occur when the administrator of the first communication device manually disables MACsec on the first communication device while the first communication device is in a secure MKA session with the second communication device.

[0057] In the example, MKA removal information can be carried in the SAK USE parameter set in the MKPDU.

[0058] Figure 3 The MKPDU format defined in IEEE standard 802.1X-2020 is shown. Some parameter sets are defined in IEEE standard 802.1X-2020:

[0059] 1. BASIC_PARAMETER_SET = 0

[0060] 2. LIVE_PEER_LIST = 1

[0061] 3. POTENTIAL_PEER_LIST = 2

[0062] 4.SAK_USE = 3

[0063] 5.DISTRIBUTED_SAK=4

[0064] 6.DISTRIBUTED_CAK=5

[0065] 7. KMD = 6

[0066] 8. ANNOUNCEMENT = 7

[0067] 9. ICV_INDICATOR=255.

[0068] Figure 4 The format of the SAK USE parameter set according to an embodiment of the present disclosure is shown. The "X" bit in the SAK USE parameter set can be used as MKA teardown information. For example, setting the "X" bit to "1" can indicate that the first communication device will tear down the MKA session with the second communication device.

[0069] For further details on the MKPDU format and SAK USE parameter set, please refer to IEEE standard 802.1X-2020.

[0070] In another example, a new set of parameters can be defined, called the "removal" parameter set. Figure 5 The format of a teardown parameter set according to an embodiment of this disclosure is shown. New parameter set types, such as 200, can be used. As shown, the two "teardown" bits in this parameter set can be used as MKA teardown information. For example, setting the "teardown" bit to "11" can instruct the first communication device to tear down the MKA session with the second communication device.

[0071] Here, the teardown parameter set may include the AES key wrapper of the SAK associated with the MKA session. According to IEEE standard 802.1X-2020, each distributed SAK should be protected by an AES key wrapper, as specified in Internet Engineering Task Force (IETF) Request for Comment (RFC) 3394, which is incorporated herein by reference in its entirety. The default initial value (IV) of the AES key wrapper as defined in RFC 3394 should be used. Upon receiving the teardown parameter set, participants should always verify the current SAK using the AES algorithm specified in the Basic parameter set. This prevents unauthorized denial-of-service attacks.

[0072] In the example, for instance, after box 210, the first communication device can terminate the MKA session and send unencrypted data to the second communication device. Here, the operation of terminating the MKA session may include: deleting the MKA participants associated with the MKA session respectively with the first and second communication devices, and deleting the SAK associated with the MKA session.

[0073] At box 220, the first communication device receives unencrypted data from the second communication device. This unencrypted data is sent by the second communication device in response to receiving MKA teardown information.

[0074] Figure 6 This is a flowchart illustrating a method 600 according to an embodiment of the present disclosure. Method 600 can be performed by a second communication device, which can be, for example, a router or any suitable device supporting the MKA protocol.

[0075] At box 610, the second communication device receives MKA teardown information from the first communication device, which instructs the first communication device to tear down the MKA session with the second communication device.

[0076] Here, the MKA removal information can be carried in the SAK USE parameter set or the removal parameter set in the MKPDU. For details, please refer to the above combination method 200 and... Figure 4 and Figure 5 The given description.

[0077] In the example, the parameter set to be removed may include an AES key wrapper around the SAK associated with the MKA session. For details, please refer to the combination of method 200 above. Figure 5 The given description. Therefore, the second communication device can verify the MKA teardown information based on the AES key wrapping of SAK.

[0078] In this example, the first communication device can act as a key server, and the second communication device can act as a client. In this case, the second communication device can terminate the MKA session in response to an MKA teardown message. The operation of terminating the MKA session may include: deleting the MKA participants associated with the first and second communication devices respectively, and deleting the SAK associated with the MKA session.

[0079] In another example, the first communication device can act as a client, and the second communication device can act as a key server. In this case, when no other active clients exist in the MKA session, the second communication device can terminate the MKA session in response to an MKA teardown message. Here, the operation of terminating the MKA session may include: deleting the MKA participants associated with the first and second communication devices respectively, and deleting the SAK associated with the MKA session. When at least one other active client exists in the MKA session, the second communication device can delete the MKA participants associated with the first and second communication devices respectively in response to the MKA teardown message (i.e., without deleting the SAK associated with the MKA session, as it will be used between the key server and the active clients). In this context, a participant is "active" when it demonstrates its "activity" by periodically sending MKPDUs during the MKA's lifetime and is thus identified as an active peer by another participant.

[0080] At box 620, the second communication device sends unencrypted data to the first communication device. In the example, unencrypted data can be sent in response to successful verification of the MKA teardown information.

[0081] In addition, after receiving the MKA removal information, the second communication device can receive unencrypted data from the first communication device.

[0082] The following will refer to Figure 7 To further explain methods 200 and 600 above, Figure 7 An example of the process for tearing down an MKA session between device A and device B is shown.

[0083] As shown in the figure, in step 1, device A and device B perform MKA session negotiation with each other. In step 2, after successful negotiation, an MKA session is established between device A and device B, and the MKA session is in a secure state. In step 3, device A and device B send encrypted data to each other.

[0084] At step 4, MACsec is disabled on device B, and device B begins tearing down the MKA session (e.g., by removing device A and device B from the MKA participants in the MKA session and deleting the SAK associated with the MKA session). At this point, at step 5, device B sends MKA teardown information to device A (see, for example...). Figure 4 or Figure 5 The MKA teardown message informs device A that device B will tear down the MKA session. Device A can, for example, wrap the MKA with an AES key based on SAK (see example...). Figure 5 To verify the MKA teardown information, in step 6, if device A is a client (in this case, device B is a key server), or if device A is a key server and there are no other active clients (other than device B) in the MKA session, then device A can tear down the MKA session (e.g., by removing device A and device B from the MKA participants of the MKA session and removing the SAK associated with the MKA session); or, if device A is a key server and there are at least one active client (other than device B) in the MKA session, then only device A and device B are removed from the MKA participants of the MKA session.

[0085] At step 7, a secure MKA session does not exist between device A and device B, or the MKA session between device A and device B becomes insecure. At step 8, device A and device B send encrypted data to each other.

[0086] The transmission and processing of MKA teardown information can take approximately 20 milliseconds, while the MKA lifetime may take 6 to 18 seconds to expire. According to this disclosure, by introducing MKA teardown information, service interruption time and / or business loss can be significantly reduced.

[0087] Figure 8 This is a block diagram of a first communication device 800 according to an embodiment of the present disclosure.

[0088] The first communication device 800 includes a communication interface 810, a processor 820, and a memory 830.

[0089] Memory 830 may contain instructions executable by processor 820, thereby enabling the first communication device 800 to perform, for example, previously combined... Figure 2 The described process involves actions. Specifically, memory 830 may contain instructions executable by processor 820, thereby enabling the first communication device 800 to: send an MKA teardown message to the second communication device in response to MACsec becoming unavailable in a secure MKA session, the MKA teardown message instructing the first communication device to tear down the MKA session with the second communication device; and receive unencrypted data from the second communication device.

[0090] In this embodiment, the MKA removal information can be carried in the SAK USE parameter set or the removal parameter set in the MKPDU.

[0091] In an embodiment, the teardown parameter set may include an AES key wrapper for the SAK associated with the MKA session.

[0092] In an embodiment, the memory 830 may also contain instructions executable by the processor 820, thereby enabling the first communication device 800 to: dismantle the MKA session and send unencrypted data to the second communication device.

[0093] In an embodiment, the operation of dismantling an MKA session may include: deleting the MKA participants associated with the first communication device and the second communication device respectively, and deleting the SAK associated with the MKA session.

[0094] In an embodiment, MACsec becoming unavailable may include MACsec being disabled at the first communication device.

[0095] Figure 9 This is a block diagram of a second communication device 900 according to an embodiment of the present disclosure.

[0096] The second communication device 900 includes a communication interface 910, a processor 920, and a memory 930.

[0097] Memory 930 may contain instructions executable by processor 920, thereby enabling the second communication device 900 to perform, for example, previously combined... Figure 6 The described process involves actions. Specifically, memory 930 may contain instructions executable by processor 920, thereby enabling the second communication device 900 to: receive MKA teardown information from the first communication device, the MKA teardown information instructing the first communication device to tear down the MKA session with the second communication device; and send unencrypted data to the first communication device.

[0098] In this embodiment, the MKA removal information can be carried in the SAK USE parameter set or the removal parameter set in the MKPDU.

[0099] In an embodiment, the teardown parameter set may include an AES key wrapper for the SAK associated with the MKA session.

[0100] In an embodiment, the memory 930 may further contain instructions executable by the processor 920, thereby enabling the second communication device 900 to verify MKA teardown information by wrapping an AES key based on SAK. Unencrypted data may be sent in response to successful verification of the MKA teardown information.

[0101] In this embodiment, the first communication device may act as a key server, and the second communication device may act as a client. The memory 930 may also contain instructions executable by the processor 920, thereby enabling the second communication device 900 to: terminate the MKA session in response to an MKA teardown message.

[0102] In this embodiment, the first communication device may act as a client, and the second communication device may act as a key server. The memory 930 may also contain instructions executable by the processor 920, thereby enabling the second communication device 900 to: terminate the MKA session in response to an MKA teardown message when no other active client exists in the MKA session; or delete the MKA participants associated with the first and second communication devices respectively in response to an MKA teardown message when at least one other active client exists in the MKA session.

[0103] In an embodiment, the operation of dismantling an MKA session may include: deleting the MKA participants associated with the first communication device and the second communication device respectively, and deleting the SAK associated with the MKA session.

[0104] Specifically, the memory 930 may contain instructions executable by the processor 920, thereby enabling the second communication device 900 to: receive unencrypted data from the first communication device after receiving MKA teardown information.

[0105] This disclosure also provides at least one computer program product in the form of non-volatile or volatile memory, such as a non-transitory computer-readable storage medium, electrically erasable programmable read-only memory (EEPROM), flash memory, and hard disk drive. The computer program product includes a computer program. The computer program includes, when executed by processor 820, causing the first communication device 800 to perform, for example, the above-described... Figure 2 The code / computer-readable instructions describing the actions of the process; or, when executed by processor 920, causing second communication device 900 to execute, for example, in combination with the above. Figure 6 The code / computer-readable instructions describing the actions of the process.

[0106] Computer program products can be configured as computer program code constructed from computer program modules. Computer program modules are essentially executable. Figure 2 or Figure 6 The actions of the process shown.

[0107] The processor may be a single CPU (Central Processing Unit), but may also include two or more processing units. For example, the processor may include a general-purpose microprocessor, an instruction set processor, and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)). The processor may also include onboard memory for caching purposes. The computer program may be carried in a computer program product connected to the processor. The computer program product may include a non-transitory computer-readable storage medium storing the computer program. For example, the computer program product may be flash memory, random access memory (RAM), read-only memory (ROM), or EEPROM, and in alternative embodiments, the aforementioned computer program modules may be distributed across different computer program products in the form of memory.

[0108] The present disclosure has been described above with reference to its embodiments. It should be understood that various modifications, substitutions, and additions can be made by those skilled in the art without departing from the spirit and scope of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific embodiments described above, but is defined only by the appended claims.

Claims

1. A method (200) in a first communication device, comprising: In response to the Media Access Control Security (MACsec) becoming unavailable in a secure MACsec Key Agreement (MKA) session, a (210) MKA teardown message is sent to a second communication device, the MKA teardown message instructing the first communication device to tear down the MKA session with the second communication device; and Receive (220) unencrypted data from the second communication device.

2. The method (200) according to claim 2, wherein, The MKA teardown information is carried in the secure associated key SAK USE parameter set or teardown parameter set in the MACsec key protocol data unit MKPDU.

3. The method (200) according to claim 2, wherein, The teardown parameter set includes an Advanced Encryption Standard (AES) key wrapper for the SAK associated with the MKA session.

4. The method (200) according to any one of claims 1 to 3, further comprising: Dismantle the MKA session; as well as Send unencrypted data to the second communication device.

5. The method (200) according to claim 4, wherein, The removal of the MKA session includes: Delete the MKA participants associated with the first communication device and the second communication device, respectively, in the MKA session; and Delete the SAK associated with the MKA session.

6. The method (200) according to any one of claims 1 to 5, wherein, The MACsec becoming unavailable includes the MACsec being disabled at the first communication device.

7. A method (600) in a second communication device, comprising: Receive (610) Media Access Control Security "MACsec" Key Agreement MKA teardown information (610) from the first communication device, the MKA teardown information instructing the first communication device to tear down the MKA session with the second communication device; and Send (620) unencrypted data to the first communication device.

8. The method (600) according to claim 7, wherein, The MKA teardown information is carried in the secure associated key SAK USE parameter set or teardown parameter set in the MACsec key protocol data unit MKPDU.

9. The method (600) according to claim 8, wherein, The teardown parameter set includes an Advanced Encryption Standard (AES) key wrapper for the SAK associated with the MKA session.

10. The method (600) according to claim 9, further comprising: The MKA teardown information is verified based on the AES key wrapping of the SAK. The unencrypted data is sent in response to the successful verification of the MKA removal information.

11. The method (600) according to any one of claims 7 to 10, wherein, The first communication device acts as a key server, and the second communication device acts as a client, wherein the method (600) further includes: In response to the MKA teardown message, the MKA session is torn down.

12. The method (600) according to any one of claims 7 to 10, wherein, The first communication device acts as a client, and the second communication device acts as a key server, wherein the method (600) further includes: When there are no other active clients in the MKA session, the MKA session is terminated in response to the MKA teardown information; or When at least one other active client exists in the MKA session, in response to the MKA teardown information, the MKA participants associated with the first communication device and the second communication device, respectively, are deleted from the MKA session.

13. The method (600) according to claim 11 or 12, wherein, The removal of the MKA session includes: Delete the MKA participants associated with the first communication device and the second communication device, respectively, in the MKA session; and Delete the SAK associated with the MKA session.

14. The method (600) according to any one of claims 7 to 13, further comprising: After receiving the MKA removal information Receive unencrypted data from the first communication device.

15. A first communication device (800) comprising a communication interface (810), a processor (820), and a memory (830), the memory (830) comprising instructions executable by the processor (820), thereby enabling the first communication device (800) to operate to perform the method according to any one of claims 1 to 6.

16. A computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions, when executed by a processor of a first communication device, configuring the first communication device to perform the method according to any one of claims 1 to 6.

17. A second communication device (900) includes a communication interface (910), a processor (920), and a memory (930), the memory (930) including instructions executable by the processor (920), thereby enabling the second communication device (900) to operate to perform the method according to any one of claims 7 to 14.

18. A computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions, when executed by a processor of a second communication device, configuring the second communication device to perform the method according to any one of claims 7 to 14.

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