System and method for managing communications between contactless devices

Abstract

Various embodiments of the present disclosure are directed to systems and methods for managing communications between contactless devices. The present disclosure is directed to modified NFC frames used by a reader and a selected device during at least a portion of the communication between the reader and the selected device. The reader and the selected device store modification rules for modifying the frames. Devices that do not store these modification rules will discard received modified frames.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of European Patent Application No. 21157687.1 filed on February 17, 2021, which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention relate to the field of contactless communications, such as Near Field Communications (NFC), and more particularly to frames used during communications between contactless devices. Background Art

[0004] Near Field Communication (better known to those skilled in the art as NFC) is a wireless connection technology that allows short-range (e.g. 10 cm) communication between electronic devices, such as a contactless smart card or tag or between a mobile device and a reader.

[0005] NFC technology is particularly well suited for connecting any type of user device and allows for quick and easy communication.

[0006] A contactless device is a device capable of exchanging information with a contactless reader via an antenna according to a contactless communication protocol.

[0007] An NFC device, which is a contactless device, is a device that is compatible with the NFC technology.

[0008] NFC technology is an open standard technology platform in ISO / IEC 18092, ISO / IEC 21481, NFC Forum and EMVCo, but combines many existing standards, such as Type A and Type B protocols defined in ISO-14443, ISO-15693 (Type V) or FeliCA JIS X6319-4 (Type F), which may be communication protocols that can be used for NFC technology.

[0009] Contactless technology can also be used with radio frequency identification (RFID) devices that are compatible with ISO 15693 and ISO 18000-3.

[0010] When information is transmitted between the reader and the device, the reader generates a magnetic field via its antenna, which in the commonly used standard is usually a 13.56 MHz sine wave (carrier wave).

[0011] To transmit information from the reader to the device, the reader uses amplitude modulation of the carrier wave.

[0012] The device includes a processor configured to demodulate a received carrier wave to obtain data transmitted from a reader.

[0013] For information transmission from the device to the reader, the reader generates a magnetic field (carrier wave) without modulation.

[0014] The device antenna then modulates the field generated by the reader according to the information to be transmitted. The frequency of this modulation corresponds to a subcarrier of the carrier. The frequency of this subcarrier depends on the communication protocol used and can be equal to 848kHz, for example.

[0015] This modulation is performed by modifying the load at the terminals connected to the device antenna.

[0016] Therefore, two operation modes are possible: passive mode or active mode.

[0017] In passive mode, the device inversely modulates the wave coming from the reader to transmit information and, in order to transmit the information, does not integrate a transmitter itself or a transmitter, such as a transmitter capable of generating its own magnetic field during broadcasting. Such a device without a transmitter is called a passive device, as opposed to an active device that includes a transmitter.

[0018] Typically, a passive device has no electrical power because it uses the waves from the reader to power its integrated circuit.

[0019] In the active mode of operation, both the reader and the active device generate an electromagnetic field. Typically, this mode of operation is used when the active device is equipped with a power source, such as a battery.

[0020] Each of the NFC devices (reader and device) uses a modulation scheme to transmit data. Here, again, the modulation results in an effect similar to load modification, and this is called Active Load Modulation (ALM) communication.

[0021] Compared to passive communication mode, a greater operating distance of up to 20 cm can be achieved, depending on the protocol used.

[0022] Furthermore, the use of active load modulation enables the use of very small antennas.

[0023] ALM is needed when the signal strength generated by passive load modulation is not strong enough to be detected by the reader. This can happen when the device has a small antenna or is located in a challenging environment.

[0024] The embodiments of the present invention are applicable to various contactless devices, passive devices or active devices.

[0025] As mentioned above, NFC is a ubiquitous technology based on standards that are well known in the industry. The NFC frames used during communication rely on a format that is clearly defined for each technology. Therefore, all devices that support the technology will receive and decode individual frames.

[0026] The open nature of NFC is key for applications that require interoperability but there are some drawbacks to deploying NFC in certain systems:

[0027] a) NFC communications can be easily eavesdropped and parsed because the payload format is common knowledge;

[0028] b) NFC systems without strong security mechanisms are vulnerable to replay attacks;

[0029] c) Since NFC frames rely on a format that is well defined for each technology, all devices supporting that technology will receive and decode individual frames, but frames that may not be suitable for certain recipients or devices of the NFC system will result in the reception and processing of frames that will later be discarded at the application layer.

[0030] Regarding a) and b), existing solutions based on advanced encryption and session mechanisms are robust but also expensive.

[0031] While such strong security levels may be necessary for certain high-cost / risk systems, they may not be justified for NFC systems addressing low-cost applications (e.g., disposable accessories).

[0032] Regarding c), processing the received payload requires energy, which is harvested from the reader's RF carrier.

[0033] Even when received frames are not intended for certain tags, the presence of multiple tags and their handling may negatively impact the reader's energy consumption and maximum communication range.

[0034] Therefore, another solution for improving security and communication distance is needed, especially when multiple tags are present. Summary of the invention

[0035] According to one embodiment, it is proposed to prevent replay attacks as much as possible.

[0036] According to one embodiment, it is also proposed to improve the communication range, especially in the presence of multiple tags.

[0037] According to one aspect, a method for managing communication between a first contactless device and a second contactless device is presented.

[0038] The devices exchange frames during communication having a frame format (or structure) that complies with a contactless communication standard and includes a frame start field, a frame end field, a payload field, and an error check field calculated from the payload field in a manner that complies with the communication standard.

[0039] The method according to this aspect includes storing modification rules in both devices, and for at least a part of the communication (or for the entire communication): causing the first device to modify the content of at least one frame element of each frame of at least a part of the communication according to the modification rule, so that the modified content of at least one frame element is different from the reference content of at least one frame element that complies with the communication standard, and at least one frame element includes a frame start field or a frame end field or a payload field or an error check field; causing the first device to send the modified frame to the second device; causing the second device to receive the modified frame and analyze the at least one modified frame element according to the modification rule; and if the second device identifies the at least one modified frame element, causing the second device to continue communicating.

[0040] Therefore, the method according to this aspect proposes to keep the standardized frame format or structure of the frame (keeping the same fields as included in the standardized frame) but modifying the content of, for example, at least one frame element (for example, one or more fields), such as the frame start field, resulting in such modified frames being processed only by (multiple) specific NFC systems, i.e. including, for example, readers and tags, all tags storing modification rules allowing modification of the content, while standard NFC devices, for example, should ignore these modified frames.

[0041] Attacks using common off-the-shelf tools can be prevented, and eavesdropping can be weakened using basic tools, as these tools support defined NFC technologies and standardized frames.

[0042] The increased complexity when manipulating tags, as the default reader tool may only support common NFC technologies (off-the-shelf tools, NFC-enabled smartphones, etc.), also helps prevent attacks.

[0043] Replay attacks can also be prevented on a large scale if individual systems use specific modification rules (one modification rule per system), or between each tag if each system uses individual modification rules (one modification rule per tag).

[0044] The method according to this aspect thus introduces a level of prevention mechanisms while keeping the system offline and without expensive and complex encryption and session mechanisms.

[0045] Additional frame acceptance / rejection (device addressing) is advantageously performed during actual reception. Thus, the application layer does not need to parse / digest the payload content.

[0046] Tags can reject unexpected frames, thereby eliminating the need to harvest energy from the RF field at the early moments of communication, which is particularly beneficial when the content at the beginning of the frame has been modified.

[0047] In this way, energy from the reader can be conserved to improve communication range (when power is limited) when the addressed tag needs to digest and take action.

[0048] As mentioned above, according to an advantageous embodiment, at least one frame element comprises a start-of-frame field.

[0049] According to one embodiment, the modification rules comprise a set of functions, and modifying the content of at least one frame element comprises applying at least one of the functions to a reference content of the at least one frame element to obtain a modified content different from the reference content.

[0050] When at least one of the frame elements is an error checking field, modifying the content of the error checking field may include calculating the content of the error checking field in a manner different from that indicated in the communication standard.

[0051] Both devices can apply modification rules from the beginning of the communication.

[0052] As a variant, both devices can apply the modification rules starting from a defined moment of communication.

[0053] The device may also apply the modification rules during a defined time period of the communication.

[0054] The modification rules may also comprise a set of different modification rules, and the method may therefore comprise causing the two devices to apply the set of different modification rules at different moments in the communication.

[0055] According to another aspect, a system is proposed, the system comprising at least a first contactless device and a second contactless device, the devices being configured to exchange frames having a frame format compliant with a contactless communication standard and comprising a frame start field, a frame end field, a payload, and an error check field calculated from the payload in a manner compliant with the communication standard during contactless communication.

[0056] The first device includes: a first storage medium for storing modification rules; a first processor, configured to modify the content of at least one frame element of each frame of at least a part of the communication according to the modification rules, so that the modified content of at least one frame element is different from the reference content of at least one frame element that complies with the communication standard, and at least one frame element includes a frame start field or a frame end field or a payload field or an error check field; and a transmitter, which is configured to send the modified frame to the second device.

[0057] The second device includes a second storage medium for storing the modification rule; a receiver configured to receive the modified frame; and a second processor configured to analyze at least one modified frame element according to the modification rule within each modified frame and continue communication if the at least one modified frame element is identified.

[0058] According to one embodiment, at least one frame element comprises a start of frame field.

[0059] According to one embodiment, the modification rules include a set of functions, and the first processor of the first device is configured to modify the content of at least one frame element, including by applying at least one of the functions to a reference content of the at least one frame element to obtain a modified content different from the reference content.

[0060] According to one embodiment, at least one frame element is an error checking field and the first processor of the first device is configured to modify the content of the error checking field by calculating the content of the error checking field in a manner different from that indicated in the communication standard.

[0061] According to one embodiment, the first processor of the first device and the second processor of the second device are configured to apply the modification rule from the start of the communication.

[0062] According to one embodiment, the first processor of the first device and the second processor of the second device are configured to apply the modification rule starting from a defined moment of the communication.

[0063] According to one embodiment, the first processor of the first device and the second processor of the second device are configured to apply the modification rule during a defined time period of the communication.

[0064] According to one embodiment, the modification rules include a set of different modification rules, wherein the first processor of the first device and the second processor of the second device are configured to apply the set of different modification rules at different moments in the communication.

[0065] According to another aspect, a device, for example a contactless reader, is proposed as a first device belonging to the system defined above.

[0066] According to another aspect, a device, such as a transceiver, is proposed as a second device belonging to the system defined above.

[0067] According to another aspect, an object, for example an object belonging to the field of Internet of Things (IOT), is proposed, the object comprising an antenna and a device coupled to the antenna, such as a second device. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Other advantages and features of the invention will emerge from the following detailed description and from the accompanying drawings, which are not limiting, in which:

[0069] Figure 1 A system including several contactless devices is shown;

[0070] Figure 2 A first storage medium and a second storage medium storing modification rules are shown;

[0071] Figure 3 shows a prior art standardized NFC frame;

[0072] Figure 4 shows an example modified frame that has been modified using the modification rule;

[0073] Figure 5 The modification rule function is shown;

[0074] Figure 6 The modification rule function is shown;

[0075] Figure 7 shows a prior art standardized NFC frame;

[0076] Figure 8 A modified frame with a modified SOF field is shown;

[0077] Fig. 9 shows a prior art standardized NFC frame;

[0078] Fig.10 A modified frame with a modified SOF field is shown;

[0079] Fig.11 Various ways to modify the contents of an error checking field are shown;

[0080] Fig.12 A flow chart showing management of communications between a reader and a third device using modified frames;

[0081] Fig.13 A flow chart showing management of communications between a reader and a second device using modified frames is shown;

[0082] Fig.14 shows a modified NFC frame used throughout the communication between the reader and the device;

[0083] Fig.15 A standardized NFC frame for a first portion of communication and a modified NFC frame for a latter portion of communication are shown;

[0084] Fig.16shows standardized NFC frames used at the beginning and end of a communication and modified NFC frames used in between; and

[0085] Fig.17 Different modification rules for different parts of the communication are shown. DETAILED DESCRIPTION

[0086] exist Figure 1 In the figure, reference symbol SYS denotes a system including several contactless devices.

[0087] More precisely, an object such as a contactless reader RD comprises a first contactless device DV1 coupled to a first antenna ANT1.

[0088] The object OBJ2, such as a transponder or a tag, comprises a second contactless device DV2 coupled to a second antenna ANT2.

[0089] Another object OBJ3, such as another tag, comprises a third contactless device DV3 coupled to a third antenna ANT3.

[0090] In this example, the system SYS uses NFC technology for communication between the reader RD and the objects OBJ2 and OBJ3.

[0091] The first device DV1 comprises a first processor PRM1 (eg an NFC controller), a first transmitter TRM1 specifically configured to perform modulation / demodulation of an RF carrier, and a first storage medium MM1 , such as a non-transitory computer readable memory.

[0092] The structure of the first transmitter TRM1 is conventional and known per se.

[0093] The second device DV2 comprises a second processor PRM2 (eg an NFC controller), a second transmitter TRM2 of a structure known per se and configured in particular to perform a load modulation of a carrier wave, and a second storage medium MM2, such as a non-transitory computer readable memory.

[0094] The third contactless device DV3 comprises a third processor PRM3 (eg NFC controller), a third transmitter TRM3 having a structure known per se and identical to that of the second processor PRM2, and a third storage medium MM3, such as a non-transitory computer readable memory.

[0095] Of course, although Figure 1 Only one device DV2 and one device DV3 are shown in FIG. 1 , but the system SYS may include several devices DV2 and several devices DV3 .

[0096] like Figure 2As shown, the first storage medium MM1 and the second storage medium MM2 store modification rules MDFR intended for modifying at least some frames exchanged during communication between the reader RD and an object OBJ2 comprising a second contactless device DV2, as will be explained in more detail below.

[0097] But the modification rules are not comprised in the third storage medium MM3 of the third device DV3.

[0098] Therefore, as will be explained in more detail hereinafter, the third device DV3 will not be able to process the modified frames sent by the reader RD.

[0099] Figure 3 A standardized frame STD conforming to one of the standards used within the NFC platform is schematically shown.

[0100] Such a standardized frame STDFR comprises a start of frame field SoF, a payload field PLD comprising the data sent or received within the frame, an error check field EoD comprising here two bytes CRC1 and CRC2. The error check field EoD allows checking for transmission errors and is calculated from the payload PLD in a manner conforming to the communication standard used.

[0101] The standardized frame STD also includes an end-of-frame field EoF.

[0102] The third contactless device DV3 is intended to interpret and process such a standardized frame STDFR.

[0103] Figure 4 An example of a modified frame MFR is schematically shown, which has been modified relative to a standardized frame STDFR by using a modification rule MDFR.

[0104] As will be explained in more detail later, these modified frames MFR may be exchanged between the reader RD and the second device DVD from the beginning and during the entire communication or only during a part of the communication or only for specific commands.

[0105] Such a modified frame MFR has the same format or structure as the one in the standardized frame STDFR. In other words, the format or structure of the modified frame MFR still includes the frame start field FLD1, the payload field PLD, the error check field FLD2 and the frame end field FLD3.

[0106] However, the content of at least one frame element of the frame is modified relative to the reference content of the corresponding frame element of the standardized frame STDFR.

[0107] exist Figure 4 In the example shown, the content of all frame elements of the frame have been modified.

[0108] However, at least one frame element or some frame elements of a frame may be modified.

[0109] For example, only the frame start field FLD1 may be modified while keeping other frame elements unmodified.

[0110] It is also possible to modify only the frame end field FLD3 or only the error check field FLD2.

[0111] like Figure 4 As shown, the modification rule may include a set of functions f applied to the reference content of the frame elements to obtain the modified content. s 、f d 、f c and f e .

[0112] like Figure 5 As shown, these functions f are selected s 、f d 、f c and f e , so that the modified contents obtained by applying these functions to the corresponding reference contents of the frame elements are different from these corresponding reference contents.

[0113] For example, Figure 6 As shown in the diagram in , such a function fi applied to content "a" may be equal to !a (! denotes logical negation).

[0114] As a variant, such a function fi applied to content “a” may be a logical exclusive OR function of “a” and a constant C.

[0115] As a variant, the constant C can be replaced by different values ​​K associated with different contents an n .

[0116] Figure 8 Shown for modification Figure 7 Another possible form of the start of frame field SoF of the standardized frame STDFR is shown.

[0117] More precisely, in this example of a standardized frame STDFR, the start of frame field SoF comprises S bits before the first data byte of the payload PLD (note that Figure 7 In the figure, P represents the parity bit).

[0118] exist Figure 8 In the modified frame MFR of FIG. 1 , the modified frame start field FLD1 may include n bits added after the S bits.

[0119] Fig.10 The diagram shows the Fig. 9Another example of a frame start field (or frame end field) of an example of a standardized frame STDFR is shown.

[0120] In this example, in compliance with standard ISO 15 693, the modulated pulse is used to signal a start of frame field SoF of a standardized frame FTDFR.

[0121] exist Fig.10 In FIG. 5 , the modification rule may include a modified pattern of these modulation pulses to signal a modified frame start field FLD1.

[0122] Regarding the check error field, although the check error field can be calculated according to the method defined in the communication standard and then a function is applied to modify the obtained content of the check error field, it can also be as follows Fig.11 The contents of the error checking field are shown to be modified by calculating the contents of the error checking field in a manner different from that dictated by the communication standard.

[0123] More precisely, the error checking field is usually calculated according to the standard ISO 13239 by using a polynomial and a standardized initial value STDIV.

[0124] The normalized initial value depends on the communication standard used.

[0125] It is also possible to invert or not invert the obtained results.

[0126] Also, in order to modify the content of the check error field, the initial value may be modified and another initial value MIV may be used, for example.

[0127] For example, four initial values ​​MIV0, MIV1, MIV2, and MIV3 may be used that are respectively different from the standardized initial values ​​STDIV associated with the four illustrated standards.

[0128] Now more specifically refer to Fig.12 and the following to illustrate an example of communication management between a reader RD and several devices DV2 and DV3.

[0129] Fig.12 More specifically the management of the communication between the reader RD and the third device DV3 is shown, wherein the reader uses modified frames.

[0130] In step ST120 , the device DV3 verifies the presence of the modulation.

[0131] If there is modulation, during a step ST121 , the third processor PRM3 of the device DV3 analyses the start of frame field SoF.

[0132] If it is assumed that the start of frame field has been modified according to the modification rule, this modified start of frame field is not the expected start of frame field SoF of the device DV3.

[0133] Therefore, the frame is rejected and the communication is interrupted.

[0134] For example, if the frame start field has not been modified in the modified frame and if it is assumed that the frame end field has been modified, step ST122 is performed, including the start of reception.

[0135] The incoming data is stored in device DV3 (step 123).

[0136] Then, in step ST124, detection of the end-of-frame field EoF is performed.

[0137] Since the end-of-frame field has been modified, the modified end-of-frame field is not the expected end-of-frame field EoF, and thus the device DV3 does not detect the end-of-frame field EoF.

[0138] Therefore, communication was interrupted again.

[0139] If it is assumed that in the modified frame only the check error field has been modified but neither the frame start field nor the frame end field has been modified, then in step ST124 the frame end field is detected and in step ST125 a transmission error is checked.

[0140] Since the check error field does not correspond to the standardized check error field, in step ST126, the reception is not considered to be correct, and in step ST127, the communication is terminated.

[0141] Fig.13 The management of the communication between the reader RD and the second device DV2 using modified frames is shown.

[0142] exist Fig.13 In the example, it is assumed that the frame start field, the check error field and the frame end field have been modified according to the modification rules.

[0143] In step ST130, the presence of modulation is verified.

[0144] If modulation is present, the frame start field FLD1 is analyzed, and if the field FLD1 is an expected field in step ST131, reception may be started in step ST132.

[0145] If the modified field FLD1 is not the expected field, the frame is discarded and the communication is interrupted.

[0146] In step ST133, the incoming data is stored.

[0147] Then, in step ST134, the frame end field FLD3 is analyzed.

[0148] If the field does not correspond to the expected field taking into account the modification rules, the communication is again interrupted.

[0149] Otherwise, in step ST135, a transmission error is checked.

[0150] If the received check error field FLD2 corresponds to the expected check error field, then in step ST136 the reception is considered to be correct and in step ST137 the payload can be parsed.

[0151] If the reception is not deemed correct, the communication is aborted.

[0152] In step ST138, if, for example, the received command is not the expected command, the communication is also terminated.

[0153] Otherwise, the process continues.

[0154] In other words, for modified frames, if the expected SoF is not satisfied (frame mismatch), the receiving process of the NFC system may discard the incoming reception.

[0155] In cases where SoF is not expected to be ignored, an unforeseen EoF may also cause the frame to be ignored.

[0156] In case framing errors are ignored (SoF and EoF), the data integrity check should raise a transmission error due to a mismatched CRC field.

[0157] Thus, by having modified the NFC frame, only the intended recipient(s) will be triggered (storing the modification rules) starting from an early moment of actual reception, without relying on subsequent processing at the application layer.

[0158] The use of modified frames thus allows to give some selected or desired devices (receivers) a certain level of security, in particular against replay attacks.

[0159] Furthermore, since devices not implementing the modification rules cannot interpret received modified frames and thus interrupt communication, the energy consumed by the reader is reduced and the communication range with selected (desired) devices containing the modification rules is increased.

[0160] Now turn to Fig.14 , it can be seen that the modified NFC frame MFR can be used during the entire communication between the reader and the device, from the beginning to the end of the communication.

[0161] like Fig.15As shown, the standardized NFC frame STDFR can also be used from the beginning of the communication to the time t1. Then, from t1 to the end of the communication, the modified NFC frame MFR is used.

[0162] like Fig.16 As shown, it is also possible to use the modified NFC frame MFR between the time t1 and the time t2 of the communication, while using the standardized NFC frame STDFR during the other periods of the communication.

[0163] like Fig.17 As shown, the modification rules MDFR may also include a set of different modification rules MDFR1 - MDFR4 .

[0164] And, if Fig.17 As shown, for example, a modified frame MFR1 modified according to a first set of modification rules MDFR1 is used from the beginning of the communication until the instant t1.

[0165] A frame MFR2 modified according to the second set of modification rules MDFR2 will be used from t1 to t2.

[0166] The frame MFR3 modified according to the third set of modification rules MDFR3 will be used from t2 to t3, and the frame MFR4 modified according to the fourth set of modification rules MDFR4 will be used from t3 to the end of the communication.

[0167] These different times can be programmed and stored in the reader and the selected device DV2.

[0168] These moments may be implemented by counters that increment or decrement from the start of the communication, or may correspond to, for example, the start or end of a specific phase of the communication (tag activation, anti-collision, acquisition of a tag identifier (UID), etc.), or may correspond to the transmission / reception of defined commands, these examples being non-limiting.

[0169] As mentioned above, the reader and the selected device DV2 share the modification rules MFR, ie share the same configuration.

[0170] Several possibilities can be used to distribute modification rules or configurations to readers and corresponding selected devices.

[0171] These modification rules can thus be distributed during production of the reader and selected devices DV2.

[0172] Such allocation can also be performed during production, but this can be changed by manual operation.

[0173] For example, the modification rules may be changed in the reader by a software / firmware update and in the selected device DV2 (eg a card) by a contact interface compliant with standard ISO7816.

[0174] It is also possible to perform allocation during production and change the modification rules MFR when triggered by the backend.

[0175] More precisely, these modification rules can be changed in the reader through automatic software / firmware updates.

[0176] For example, modification rules in a contactless device comprised in a card may be updated, for example, by a reader using dedicated RF commands.

Claims

1. A method for managing communication between a first contactless device and a second contactless device, the method comprising: exchanging frames by the first contactless device and the second contactless device during the communication, the frames having a frame format conforming to a contactless communication standard and comprising a frame start field, a frame end field, a payload field, and an error check field calculated from the payload field in accordance with the communication standard; storing modification rules in two contactless devices; modifying, by the first contactless device, the content of at least one frame element of each frame of at least a portion of the communication according to the modification rule, such that the modified content of the at least one frame element is different from the reference content of the at least one frame element conforming to the communication standard, the at least one frame element comprising the frame start field or the frame end field or the payload field or the error check field, sending, by the first contactless device to the second contactless device, the frame having the modified content, receiving, by the second contactless device, the frame having the modified content; analyzing, by the second contactless device, the modified at least one frame element according to the modification rule; as well as In response to the second contactless device identifying the modified at least one frame element, continuing the communication by the second contactless device; wherein the modification rules include a set of functions, and modifying the content of the at least one frame element includes applying at least one of the functions to the reference content of the at least one frame element to obtain the modified content that is different from the reference content; and Wherein the first contactless device is a contactless reader and the second contactless device is a transponder. The method of claim 1 , wherein the at least one frame element comprises the start of frame field.

3. The method of claim 1, wherein the at least one frame element is the error checking field, and modifying the content of the error checking field comprises calculating the content of the error checking field in a manner different from the communication standard. 4 . The method of claim 1 , further comprising applying the modification rule by two contactless devices from the beginning of the communication.

5. The method of claim 1, further comprising applying the modification rule by two contactless devices starting from a defined time during the communication.

6. The method of claim 5, further comprising applying the modification rule by two contactless devices during a defined time period of the communication.

7. The method of claim 1, wherein the modification rules comprise a set of different modification rules, and the method comprises applying, by two contactless devices, different modification rules from the set at different moments in the communication.

8. A first contactless device, wherein the first contactless device and the second contactless device are configured to exchange frames during contactless communication, the frames having a frame format that complies with a contactless communication standard and comprising a frame start field, a frame end field, a payload field, and an error check field calculated from the payload field in accordance with the communication standard, wherein the first contactless device comprises: a first storage medium, the first storage medium being configured to store modification rules; a first processor, the first processor being configured to: modify the content of at least one frame element of each frame of at least a portion of the communication according to the modification rule, so that the modified content of the at least one frame element is different from the reference content of the at least one frame element conforming to the communication standard, the at least one frame element comprising the frame start field or the frame end field or the payload field or the error check field; as well as a transmitter configured to send the frame with the modified content to the second contactless device; wherein the modification rules comprise a set of functions, and wherein the first processor being configured to modify the content of the at least one frame element comprises the first processor being configured to apply at least one of the functions to the reference content of the at least one frame element to obtain the modified content that is different from the reference content; and Wherein the first contactless device is a contactless reader and the second contactless device is a transponder.

9. The first contactless device of claim 8, wherein the at least one frame element comprises the frame start field.

10. The first contactless device of claim 8, wherein the at least one frame element is the error check field, and wherein the first processor is configured to modify the content of the error check field by calculating the modified content of the error check field in a manner different from an error check field calculation of the communication standard.

11. The first contactless device of claim 8, wherein the first processor is configured to apply the modification rule from the start of the communication.

12. The first contactless device of claim 8, wherein the first processor is configured to apply the modification rule starting from a defined time during the communication.

13. The first contactless device of claim 12, wherein the first processor is configured to apply the modification rule during a defined time period of the communication.

14. The first contactless device of claim 8, wherein the modification rules comprise a set of different modification rules, and wherein the first processor is configured to apply different modification rules in the set at different times of the communication.

15. A second contactless device, wherein the second contactless device and the first contactless device are configured to exchange frames during contactless communication, the frames having a frame format that complies with a contactless communication standard and comprising a frame start field, a frame end field, a payload field, and an error check field calculated from the payload field in accordance with the communication standard, wherein the second contactless device comprises: a second storage medium, the second storage medium being configured to store the modification rule; a receiver configured to receive a modified frame from the first contactless device, wherein the content of at least one frame element of each frame of at least a portion of the communication is modified according to the modification rule so that the modified content of the at least one frame element is different from a reference content of the at least one frame element conforming to the communication standard, the at least one frame element comprising the frame start field or the frame end field or the payload field or the error check field; as well as A second processor, wherein the second processor is configured to: within each modified frame, analyzing the modified at least one frame element according to the modification rule; and continuing said communicating in response to identifying said at least one frame element that has been modified; wherein the modification rules comprise a set of functions, wherein the modified content of the at least one frame element is derived from at least one of the functions applied to the reference content of the at least one frame element, and wherein the modified content is different from the reference content; and Wherein the first contactless device is a contactless reader and the second contactless device is a transponder.

16. The second contactless device of claim 15, wherein the at least one frame element comprises the frame start field.

17. The second contactless device of claim 15, wherein the at least one frame element is an error check field, and wherein the modified content of the error check field is calculated in a manner different from an error check field calculation of the communication standard.

18. The second contactless device of claim 15, wherein the second processor is configured to apply the modification rule from the start of the communication.

19. The second contactless device of claim 15, wherein the second processor is configured to apply the modification rule starting from a defined time during the communication.

20. The second contactless device of claim 19, wherein the second processor is configured to apply the modification rule during a defined time period of the communication.

21. The second contactless device of claim 15, wherein the modification rules comprise a set of different modification rules, and wherein the second processor is configured to apply different modification rules in the set at different times of the communication.

22. The second contactless device of claim 15, further comprising an antenna coupled to the receiver.

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