Communication equipment and integrated circuits

Abstract

This reduces the time it takes to resolve communication anomalies and restore normal encrypted communication. [Solution] The communication device 2a includes a decryption processing unit 20a that decrypts the ciphertext sent from the transmitting communication device 1a, and an abnormality notification unit 23 that notifies the decryption processing unit 20a of the abnormality that has occurred from the time an abnormality occurs in communication between the communication device 1a and itself until the abnormality is resolved. The decryption processing unit 20a maintains the decryption processing settings from before the notification while it receives a notification from the abnormality notification unit 23.

Description

【Technical Field】 【0001】 The present invention relates to an encryption / decryption technique used in a digital coherent optical transmission system, and particularly relates to improving the disturbance resistance in the encryption process of a digital coherent optical transmission system. 【Background Art】 【0002】 In the current standard of a digital coherent optical transmission system, when a disturbance state continuously occurs in a network that transmits a signal from a transmission device to a reception device, there is a possibility that the encryption key or the type of encryption algorithm may be switched unintentionally (Non-Patent Documents 1 to 4). 【0003】 Fig. 11 shows the frame structure of a main signal transmitted from a communication device on the transmission side to a communication device on the reception side. The main signal is the FlexO frame shown in Fig. 11. The FlexOsec area in the EOH (Extended Overhead) field in Fig. 11 is mainly used by the encryption processing unit of the communication device on the transmission side and the decryption processing unit of the communication device on the reception side. Two bits out of the 39th byte of the FlexOsec area are used to transmit and receive an encryption key index signal (KI: Key Index), and the remaining 6 bits are used to transmit and receive an encryption algorithm type signal (CST: Cipher Suite Type). Further, the 37th byte of the FlexOsec area is used to transmit and receive information (KCC: Key exchange Communication Channel) for generating an encryption key during a key exchange process. 【0004】 Figures 12 to 15 illustrate the flow of encrypted communication in a conventional digital coherent optical transmission system. In the initial state shown in Figure 12(A), the encryption processing unit 10 of the transmitting communication device 1 sends a FlexO frame signal with a CST value set to "0" to the receiving communication device 2. Setting the CST value to "0" means turning off (bypassing) the encryption / decryption process and communicating in plaintext. The decryption processing unit 20 of the communication device 2 turns off the decryption process upon receiving a FlexO frame signal with a CST value of "0". 【0005】 Next, a key exchange process takes place between the encryption processing unit 10 and the decryption processing unit 20 (Figure 12(B)). During the key exchange process, information for generating a common encryption key is exchanged between the encryption processing unit 10 and the decryption processing unit 20 via the KCC signal of the FlexO frame. Details of the key exchange process will be described later. 【0006】 Once a common encryption key is generated for both the encryption processing unit 10 and the decryption processing unit 20 through the key exchange process, encrypted communication begins (Figure 13(A)). The encryption processing unit 10 sends FlexO frame signals #i, #i+1, #i+2, #i+3,.... with the KI value set to "1" and the CST value set to "1" to the communication device 2. At this time, the encryption processing unit 10 stores the ciphertext, which is the plaintext to be transmitted, in the payload of the FlexO frame signals #i, #i+1, #i+2, #i+3,.... Setting the KI value to "1" means that encryption key #1 is to be used. Setting the CST value to "1" means that GCM is to be used as the encryption algorithm. 【0007】 When the decryption processing unit 20 of the communication device 2 receives FlexO frame signals #i, #i+1, #i+2, #i+3, ..., it uses encryption key #1 according to the frame's KI value and GCM as the encryption algorithm according to the CST value to decrypt the ciphertext stored in the payload of FlexO frame signals #i, #i+1, #i+2, #i+3, .... Here, since the algorithm type and encryption key match between the encryption processing unit 10 and the decryption processing unit 20, the ciphertext is successfully decrypted. 【0008】 Figure 13(B) shows a disturbance occurring in the network 3 connecting communication device 1 and communication device 2. Similarly, the encryption processing unit 10 of communication device 1 sets the KI value to "1" and the CST value to "1" and transmits the FlexO frame signals #i, #i+1, #i+2, #i+3, ... to communication device 2. 【0009】 However, due to a disturbance in network 3, the FlexO frame signals #i, #i+1, #i+2, #i+3, ... received by communication device 2 have abnormalities in the KI value, CST value, and ciphertext. In the example in Figure 13(B), the KI value set to "1" on the transmitting side has changed to a value other than "1" on the receiving side. Similarly, the CST value set to "1" on the transmitting side has changed to a value other than "1" on the receiving side, for example, a value that specifies the use of GMAC as the encryption algorithm. Therefore, the decryption processing unit 20 cannot decrypt the ciphertext correctly. Note that "9.3.2.4 Cipher suite type (CST)" in Non-Patent Literature 2 does not define a value that specifies the use of GMAC as the encryption algorithm. In this document, we will explain that one of the code points (000010-110111) reserved for CST, which is scheduled to be standardized in the future, is independently defined and used as the value that specifies GMAC. 【0010】 Figure 14(A) shows the case where the disturbance continues. In the current standard, the decryption unit 20 selects the encryption key by majority vote on the KI value every four frames. In the example in Figure 14(A), the receiving side coincidentally has a state where the KI values ​​of FlexO frame signals #i, #i+1, and #i+2 are "3" and the KI value of FlexO frame signal #i+3 is "1". Therefore, the decryption unit 20 changes the encryption key to be used from #1 to #3 by majority vote on the KI values. Since an encryption key switch has occurred, the decryption unit 20 determines that encryption key #1 has been used and initializes it. Here, only the case where encryption key #1 is initialized is shown, but since encryption key switches can occur multiple times, it is also possible that all four encryption keys may be initialized. 【0011】 Furthermore, under the current standard, the decryption processing unit 20 determines the type of encryption algorithm if the same CST value is present for 15 consecutive frames. In the example in Figure 14(A), a state occurred by chance where the CST value specifying the use of GMAC as the encryption algorithm was present for 15 consecutive frames, so the decryption processing unit 20 decides to use GMAC as the encryption algorithm. As described above, if a disturbance occurs in network 3, unintended initialization of the encryption key or switching of the encryption algorithm may occur. 【0012】 Figure 14(B) shows the state after the disturbance has been resolved. Once the disturbance in network 3 subsides, the decryption processing unit 20 receives the correct FlexO frame signals #i,#i+1,#i+2,#i+3,····, which contain the KI value, CST value, and ciphertext. However, because the encryption keys #0 to #3 have been initialized, the decryption processing unit 20 cannot successfully decrypt the ciphertext. After this, the key exchange process shown in Figure 12(B) is performed again between the encryption processing unit 10 and the decryption processing unit 20. 【0013】 After another key exchange process, a common encryption key is generated for both the encryption processing unit 10 and the decryption processing unit 20, and encrypted communication is resumed (Figure 15). The encryption processing unit 10 sets the KI value to "2" and the CST value to "1" and sends the FlexO frame signals #i,#i+1,#i+2,#i+3,... to the receiving communication device. When the decryption processing unit 20 receives the FlexO frame signals #i,#i+1,#i+2,#i+3,..., it uses encryption key #2 according to the frame's KI value and GCM as the encryption algorithm according to the CST value to decrypt the ciphertext stored in the payload of the FlexO frame signals #i,#i+1,#i+2,#i+3,.... Here, since the algorithm type and encryption key match between the encryption processing unit 10 and the decryption processing unit 20, the ciphertext is successfully decrypted. 【0014】 Next, the key exchange process will be explained. In the key exchange process, the key generation unit 11 of communication device 1 first divides the information of its own device necessary for calculating encryption key #1, which is a common key for communication device 1 and communication device 2, and embeds the divided information D1-i, D1-(i+1), D1-(i+2), D1-(i+3), ... into the FlexO frame signal to communication device 2. Similarly, the key generation unit 21 of communication device 2 divides the information of its own device necessary for calculating encryption key #1, and embeds the divided information D2-i, D2-(i+1), D2-(i+2), D2-(i+3), ... into the FlexO frame signal to communication device 1 (Figure 16). 【0015】 Thus, as shown in Figure 17, the information D1-i, D1-(i+1), D1-(i+2), D1-(i+3), ... are each stored in different FlexO frame signals and transmitted sequentially from communication device 1 to communication device 2. Similarly, the information D2-i, D2-(i+1), D2-(i+2), D2-(i+3), ... are each stored in different FlexO frame signals and transmitted sequentially from communication device 2 to communication device 1. 【0016】 As shown in Figure 18, the key generation unit 11 of the communication device 1 extracts information D2-i, D2-(i+1), D2-(i+2), D2-(i+3), ... from the FlexO frame signal transmitted from the communication device 2. The key generation unit 11 then generates encryption key #1 based on its own information D1-i, D1-(i+1), D1-(i+2), D1-(i+3), ... and the information D2-i, D2-(i+1), D2-(i+2), D2-(i+3), ... sent from the communication device 2. 【0017】 Similarly, the key generation unit 21 of communication device 2 extracts information D1-i, D1-(i+1), D1-(i+2), D1-(i+3), ... from the FlexO frame signal transmitted from communication device 1. Then, the key generation unit 21 generates encryption key #1 based on its own information D2-i, D2-(i+1), D2-(i+2), D2-(i+3), ... and the information D1-i, D1-(i+1), D1-(i+2), D1-(i+3), ... sent from communication device 1. The key generation algorithm is the same for communication device 1 and communication device 2. Therefore, a common encryption key #1 is generated for communication device 1 and communication device 2. 【0018】 As shown in Figure 19, the key generation unit 11 of communication device 1 sets the generated encryption key #1 to the encryption processing unit 10. Similarly, the key generation unit 21 of communication device 2 sets the generated encryption key #1 to the decryption processing unit 20. This enables encrypted communication between communication device 1 and communication device 2 using encryption key #1. Up to four encryption keys can be set, so the process described in Figures 16 to 19 should be performed when generating other encryption keys. Also, the same process as in Figures 16 to 19 should be performed when exchanging keys between the encryption processing unit 22 of communication device 2 and the decryption processing unit 12 of communication device 1. 【0019】 As described above, in conventional digital coherent optical transmission systems, when an encryption key switch occurs, the encryption key that has been determined to be used is initialized. Therefore, when restoring normal encrypted communication after the network disturbance is resolved, a key exchange process is required again, which has the problem of taking time to recover. In addition, because the type of encryption algorithm switches, an unintended encryption algorithm is applied to the decryption processing unit, resulting in a period during which decryption processing is not performed using the originally expected encryption algorithm. [Prior art documents] [Non-patent literature] 【0020】 [Non-Patent Document 1] Recommendation G.798 (2023) Amendment 1 (04 / 24),<https: / / www.itu.int / rec / T-REC-G.798-202404-I!Amd1 / en> [Non-Patent Document 2] Recommendation G.709.1 / Y.1331.1 (03 / 24),<https: / / www.itu.int / rec / T-REC-G.709.1-202403-I / en> [Non-Patent Document 3] Recommendation G.709.3 (03 / 24),<https: / / www.itu.int / rec / T-REC-G.709.3-202403-I / en> [Non-Patent Document 4] Recommendation G.709.6 (03 / 24),<https: / / www.itu.int / rec / T-REC-G.709.6-202403-I / en> [Overview of the Initiative] [Problems that the invention aims to solve] 【0021】 The present invention has been made to solve the above problems, and an object thereof is to provide a communication device and an integrated circuit capable of shortening the time from the elimination of communication abnormalities to the restoration of a normal encrypted communication state. 【Means for Solving the Problems】 【0022】 The communication device of the present invention includes a decryption processing unit configured to decrypt a ciphertext sent from a communication device on the transmission side, and an abnormality notification unit configured to notify the decryption processing unit of the occurrence of an abnormality from the time when an abnormality occurs in the communication between the communication device on the transmission side and the own device until the abnormality is eliminated. The decryption processing unit is characterized in that it maintains the setting of the decryption processing before the notification while there is a notification from the abnormality notification unit. 【0023】 In addition, in one configuration example of the communication device of the present invention, the decryption processing unit is characterized in that it maintains the encryption key used before the notification while there is a notification from the abnormality notification unit. In addition, in one configuration example of the communication device of the present invention, the decryption processing unit determines an encryption key to be used by a majority decision process of encryption key index signals stored in a plurality of frame signals sent from the communication device on the transmission side when there is no notification from the abnormality notification unit, and initializes the encryption key used immediately before when a switch of the encryption key occurs. In addition, in one configuration example of the communication device of the present invention, the decryption processing unit is characterized in that it maintains the encryption algorithm type used before the notification while there is a notification from the abnormality notification unit. In addition, in one configuration example of the communication device of the present invention, the decryption processing unit determines the encryption algorithm type to be used by an equivalence determination process of encryption algorithm type signals stored in a plurality of frame signals sent from the communication device on the transmission side when there is no notification from the abnormality notification unit. 【0024】 Further, the integrated circuit of the present invention includes a decoding processing unit configured to decode a ciphertext sent from a communication device on the transmission side, and an abnormality notification unit configured to notify the decoding processing unit that an abnormality has occurred from when an abnormality occurs in communication between the communication device on the transmission side and the communication device on the reception side on which the self-chip is mounted until the abnormality is resolved. The decoding processing unit is characterized in that it maintains the setting of the decoding process before the notification while there is a notification from the abnormality notification unit. 【Advantages of the Invention】 【0025】 According to the present invention, by providing an abnormality notification unit and maintaining the setting of the decoding process before the notification while the decoding processing unit receives a notification from the abnormality notification unit, when an abnormality occurs in communication between the communication device on the transmission side and the self-device, the need for re-key exchange processing in the conventional standard is eliminated, so that the time from the resolution of the abnormality to the restoration of a normal encrypted communication state can be significantly shortened. 【Brief Description of the Drawings】 【0026】 [Figure 1] FIG. 1 is a block diagram showing the configuration of a digital coherent optical transmission system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a state in which a disturbance occurs in a network in the digital coherent optical transmission system according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing a state in which the disturbance occurring in the network in the digital coherent optical transmission system according to an embodiment of the present invention continues. [Figure 4] FIG. 4 is a flowchart for explaining the abnormality detection / notification process of the abnormality notification unit and the encryption key determination process of the decoding processing unit according to an embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart for explaining the abnormality detection / notification process of the abnormality notification unit and the encryption algorithm type determination process of the decoding processing unit according to an embodiment of the present invention. [Figure 6]Figure 6 shows the state in which disturbances that occurred in the network have been resolved in a digital coherent optical transmission system according to an embodiment of the present invention. [Figure 7] Figure 7 is a timing chart illustrating an example of the operation of the abnormality notification unit and the decoding processing unit according to an embodiment of the present invention when an abnormality occurs. [Figure 8] Figure 8 is a timing chart illustrating an example of the operation of a conventional decoding processing unit when an anomaly occurs. [Figure 9] Figure 9 is a timing chart illustrating another example of the operation of the abnormality notification unit and the decoding processing unit according to an embodiment of the present invention when an abnormality occurs. [Figure 10] Figure 10 is a timing chart illustrating another example of the operation of a conventional decoding unit in the event of an anomaly. [Figure 11] Figure 11 shows the frame structure of the main signal transmitted from the transmitting communication device to the receiving communication device. [Figure 12] Figure 12 illustrates the flow of encrypted communication in a conventional digital coherent optical transmission system. [Figure 13] Figure 13 illustrates the flow of encrypted communication in a conventional digital coherent optical transmission system. [Figure 14] Figure 14 illustrates the flow of encrypted communication in a conventional digital coherent optical transmission system. [Figure 15] Figure 15 illustrates the flow of encrypted communication in a conventional digital coherent optical transmission system. [Figure 16] Figure 16 is a diagram illustrating the key exchange process. [Figure 17] Figure 17 is a diagram illustrating the key exchange process. [Figure 18] Figure 18 is a diagram illustrating the key exchange process. [Figure 19] Figure 19 is a diagram illustrating the key exchange process. [Modes for carrying out the invention] 【0027】 Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a digital coherent optical transmission system according to an embodiment of the present invention. The digital coherent optical transmission system consists of communication devices 1a and 2a and a network 3 connecting the communication devices 1a and 2a. 【0028】 Communication device 1a includes an encryption processing unit 10, a key generation unit 11, a decryption processing unit 12a, and an error notification unit 13. Communication device 2a includes a decryption processing unit 20a, a key generation unit 21, an encryption processing unit 22, and an error notification unit 23. 【0029】 In an actual digital coherent optical transmission system, for example, a signal processing unit that performs encoding, symbol mapping, waveform shaping, and pre-equalization is required after the encryption processing units 10 and 22, a D / A conversion unit that converts the output of the signal processing unit from a digital signal to an analog signal, and an optical transmission unit that converts the output of the D / A conversion unit into an optical signal and sends it to the network 3. Furthermore, before the decoding processing units 12a and 20a, for example, an optical receiving unit that converts an optical signal received from a communication device on the opposite side via the network 3 into an electrical signal, an A / D conversion unit that converts the output of the optical receiving unit from an analog signal to a digital signal, and a signal processing unit that performs wavelength dispersion compensation, equalization, error correction, symbol demapping, and signal synchronization on the output of the A / D conversion unit are required. Since these are well-known configurations, only the main configurations of the present invention are shown in Figure 1. 【0030】 Next, the operation of the digital coherent optical transmission system of this embodiment will be described. The operation of the encryption processing units 10 and 22 and the key generation units 11 and 21 of the communication devices 1a and 2a is the same as in the conventional system. The initial state processing, key exchange processing, and encrypted communication after key exchange processing are the same as the conventional processing described in Figures 12(A), 12(B) (Figures 16 to 19), and 13(A), so the explanation will be omitted. 【0031】 Figure 2 shows a situation where a disturbance occurs in the network 3 connecting communication device 1a and communication device 2a. Similar to the case in Figure 13(B), the encryption processing unit 10 of communication device 1a sets the KI value to "1" and the CST value to "1" and sends the FlexO frame signals #i,#i+1,#i+2,#i+3,···· to communication device 2a. 【0032】 However, due to a disturbance in network 3, the FlexO frame signals #i, #i+1, #i+2, #i+3, ... received by communication device 2a have abnormalities in the KI value, CST value, and ciphertext. In the example in Figure 2, the KI value, which was set to "1" on the transmitting side, has changed to a value other than "1" on the receiving side. Similarly, the CST value, which was set to "1" on the transmitting side, has changed to a value other than "1" on the receiving side, for example, a value that specifies the use of GMAC as the encryption algorithm. Therefore, the decryption processing unit 20a cannot decrypt the ciphertext correctly. 【0033】 Figure 3 shows the case where the disturbance continues. Figure 4 is a flowchart illustrating the abnormality detection and notification process of the abnormality notification unit 23 and the encryption key determination process of the decryption processing unit 20a in this embodiment. In the conventional standard, the encryption key to be used is determined by a majority vote of KI values ​​every 4 frames. In contrast, in this embodiment, in addition to the conventional conditions, the condition for switching the encryption key is that no abnormality has been detected by the abnormality notification unit 23. 【0034】 When the abnormality notification unit 23 detects an abnormality in communication between communication device 1a and communication device 2a (YES in step S100 of Figure 4), it notifies the decoding processing unit 20a that an abnormality has occurred (step S101 of Figure 4). 【0035】 If there is no notification from the abnormality notification unit 23 (NO in step S100), the decryption processing unit 20a determines the encryption key to be used by majority voting of KI values ​​every 4 frames, as in the conventional method (Figure 4, step S102). If an encryption key switch occurs (YES in Figure 4, step S103), the decryption processing unit 20a determines that the encryption key used immediately before is no longer in use and initializes it (Figure 4, step S104). 【0036】 In the conventional standard, as shown in Figure 14(A), if the receiving side happens to have a state where the KI values ​​of FlexO frame signals #i, #i+1, and #i+2 are "3" and the KI value of FlexO frame signal #i+3 is "1", the decryption processing unit 20 changes the encryption key used from #1 to #3 and initializes the used encryption key #1. 【0037】 On the other hand, in this embodiment, if a notification is received from the abnormality notification unit 23, the decryption processing unit 20a stops the encryption key determination process and continues to use the encryption key currently in use (Figure 4, step S105). Therefore, in the example of Figure 3, the decryption processing unit 20a continues to use encryption key #1, so encryption key #1 is not initialized. In this way, in this embodiment, if a communication abnormality occurs between communication device 1a and communication device 2a, the switching of encryption keys can be suppressed, and unintended initialization of encryption keys can be prevented. As a result, in this embodiment, the encryption key exchange process is unnecessary. 【0038】 Figure 5 is a flowchart illustrating the anomaly detection and notification process of the anomaly notification unit 23 and the encryption algorithm type determination process of the decryption processing unit 20a in this embodiment. The processing of the abnormality notification unit 23 (steps S100, S101) is as described in Figure 4. 【0039】 If there is no notification from the anomaly notification unit 23 (NO in step S100), the decryption processing unit 20a decides to use the encryption algorithm type specified by the CST value if the same CST value is used for 15 consecutive frames, as in the conventional method (Figure 5, step S110). If there is a notification from the anomaly notification unit 23, the decryption processing unit 20a stops the encryption algorithm type determination process and continues to use the encryption algorithm type currently in use (Figure 5, step S111). 【0040】 In this embodiment, in addition to the conventional conditions, the condition for switching the encryption algorithm type is that no abnormality is detected by the abnormality notification unit 23. In the example in Figure 14(A), a state occurred by chance in which the CST value specifying the use of GMAC as the encryption algorithm continued for 15 frames, so the decryption processing unit 20 decides to use GMAC as the encryption algorithm. As a result, an unintended encryption algorithm type will be applied for at least 15 frames from the time the encryption algorithm type switch occurs until the disturbance is resolved. 【0041】 On the other hand, in this embodiment, if a notification is received from the anomaly notification unit 23, the process of determining the encryption algorithm type is stopped, so there is no switch from GCM to GMAC. In this way, in this embodiment, when a communication anomaly occurs between communication device 1a and communication device 2a, the switching of the encryption algorithm type can be suppressed, and the encryption algorithm type that was applied until just before the anomaly occurred can be maintained. As a result, in this embodiment, encrypted communication can be resumed without waiting for the 15-frame equivalence determination process for the CST value that was necessary after the disturbance was resolved. 【0042】 Figure 6 shows the state after the disturbance has been resolved. Once the disturbance in network 3 subsides, notifications from the anomaly notification unit 23 cease, and the decryption processing unit 20a resumes the encryption key determination process and the encryption algorithm type determination process. Furthermore, since the decryption processing unit 20a maintains the encryption key and encryption algorithm type that were applied immediately before the anomaly occurred, it can quickly resume normal encrypted communication. 【0043】 Next, the more specific operation of the abnormality notification unit 23 and the decoding processing unit 20a in this embodiment will be described. In this embodiment, it is assumed that FlexO-LR (DSP) is adopted as the FlexO standard. In the case of FlexO-LR, the types of communication abnormalities are (I) FEC (Forward Error Correction) uncorrectable and CRC (Cyclic Redundancy Check) errors, (II) OOF, and (III) LOF. 【0044】 When an uncorrectable OFEC (Open FEC), CFEC (Concatenated FEC), or proprietary FEC is detected, the anomaly notification unit 23 determines that an FEC uncorrectable error (I) has been detected. These anomalies are detected in less than one frame. When the uncorrectable error (OFEC, CFEC, non-standardized vendor-specific FEC, etc.) is resolved, the anomaly notification unit 23 determines that the FEC uncorrectable error has been resolved and terminates its notification to the decoding processing unit 20a. Additionally, when a CRC error is detected, the anomaly notification unit 23 determines that a CRC error (I) has been detected. When CRC synchronization is established, the anomaly notification unit 23 determines that the CRC error has been resolved. 【0045】 When an AM (Alignment Marker) synchronization failure is detected, the abnormality notification unit 23 determines that an OOF (Out of Function Failure) of type (II) has been detected. When AM synchronization is established, the abnormality notification unit 23 determines that the OOF has been resolved. When the OOF detection state accumulates for 3ms, the abnormality notification unit 23 determines that a LOF (Least Of Function Failure) of type (III) has been detected. When the OOF release state continues for 3ms, the abnormality notification unit 23 determines that the LOF has been resolved. The abnormalities described above in (I) to (III) are described in Chapter 16.7 of Non-Patent Literature 1. 【0046】 In this embodiment, FlexO-SR (External Framer) may also be adopted as the FlexO standard. In the case of FlexO-SR, the types of communication errors are (IV) FEC correction failure, (V) OOL, and (VI) LOL. When RS10FEC correction failure detection is detected, the error notification unit 23 determines that (IV) FEC correction failure has been detected. When RS10FEC correction failure is resolved, the error notification unit 23 determines that the FEC correction failure has been resolved. 【0047】 When either AM synchronization failure or three consecutive codewords that cannot be corrected are detected, the abnormality notification unit 23 determines that OOL (V) has been detected. When all three conditions—AM synchronization failure, Deskew error, and three consecutive codewords that cannot be corrected—are resolved, the abnormality notification unit 23 determines that OOL has been resolved. When the OOL detection state has accumulated for 3ms, the abnormality notification unit 23 determines that LOL (VI) has been detected. When the OOL release state has continued for 3ms, the abnormality notification unit 23 determines that LOL has been resolved. The abnormalities described above in (IV) to (VI) are described in Chapter 16.8 of Non-Patent Literature 1. 【0048】 Figure 7 is a timing chart illustrating the operation of the anomaly notification unit 23 and the decryption processing unit 20a in this embodiment when anomalies (I) to (III) occur. P1 in Figure 7 indicates the period during which a disturbance occurs in network 3. N1, N2, and N3 indicate the periods during which notifications are output from the anomaly notification unit 23 in response to the detection of anomalies (I), (II), and (III), respectively. FL indicates the FlexO frame signal received by communication device 2a, and KI indicates the KI value stored in the FlexO frame signal. P2 in Figure 7 indicates the period during which the KI value received by communication device 2a due to the disturbance in network 3 is an abnormal value different from the original value transmitted by communication device 1a. MR indicates the result of the majority vote of the KI value, and EK indicates the encryption key used by the decryption processing unit 20. 【0049】 In the case of anomaly detection in (I), the anomaly notification N1 is issued with a short time interval between the occurrence of the disturbance and the detection of the anomaly. Therefore, the decoding processing unit 20a can detect the anomaly before the majority vote of the KI values ​​is completed. On the other hand, in the case of anomaly detection in (III), the time interval between the resolution of the disturbance and the release of the anomaly is long. Therefore, the decoding processing unit 20a can detect the timing when sufficient time has passed since the resolution of the disturbance and the signal has stabilized. 【0050】 The decryption processing unit 20a does not accept the result of the majority vote of the KI value during the period in which any of the abnormal notifications N1 to N3 are output, as it considers the result to be an invalid value. The "×" marks in Figure 7 indicate that even though "0x2" or "0x1" was obtained as the result of the majority vote of the KI value, the decryption processing unit 20a did not accept the result of the majority vote as an invalid value. Therefore, the decryption processing unit 20a continues to maintain the encryption key #1 from before the disturbance occurred. Once all of the abnormal notifications N1 to N3 are cleared, the decryption processing unit 20a resumes the encryption key determination process in step S102 and the encryption algorithm type determination process in step S110. 【0051】 Figure 8 is a timing chart illustrating the operation of the decryption processing unit 20 of the conventional communication device 2 when abnormalities (I) to (III) occur. Although abnormality notifications N1 to N3 are not input to the conventional decryption processing unit 20, they are included here for comparison with Figure 7. The conventional decryption processing unit 20a determines the encryption key based on the result of majority voting of abnormal KI values ​​caused by the disturbance, resulting in an unintended switching of the encryption key from #1 to #2. 【0052】 Figure 9 is a timing chart illustrating the operation of the abnormality notification unit 23 and the decoding processing unit 20a in this embodiment when abnormalities (IV) to (VI) occur. N4, N5, and N6 indicate the periods during which notifications are output from the abnormality notification unit 23 in response to the detection of abnormalities (IV), (V), and (VI), respectively. For abnormality notifications N4 and N5 in response to the detection of abnormalities (IV) and (V), the time from the occurrence of the disturbance to the detection of the abnormality is short. Therefore, the decoding processing unit 20a can detect the abnormality before the majority vote of the KI value is established. On the other hand, for abnormality notification N6 in response to the detection of abnormality (VI), the time from the resolution of the disturbance to the resolution of the abnormality is long. Therefore, the decoding processing unit 20a can detect the timing when sufficient time has passed since the resolution of the disturbance and the signal has stabilized. 【0053】 The decryption processing unit 20a does not accept the result of the majority vote of the KI value during the period in which any of the abnormal notifications N4 to N6 are output, as it considers the result to be an invalid value. The "×" marks in Figure 9 indicate that even though "0x2" or "0x1" was obtained as the result of the majority vote of the KI value, the decryption processing unit 20a did not accept the result of the majority vote as an invalid value. Therefore, the decryption processing unit 20a continues to maintain the encryption key #1 from before the disturbance occurred. Once all of the abnormal notifications N4 to N6 are cleared, the decryption processing unit 20a resumes the encryption key determination process in step S102 and the encryption algorithm type determination process in step S110. 【0054】 Figure 10 is a timing chart illustrating the operation of the decryption processing unit 20 of the conventional communication device 2 when abnormalities (IV) to (VI) occur. Although abnormality notifications N4 to N6 are not input to the conventional decryption processing unit 20, they are included here for comparison with Figure 9. The conventional decryption processing unit 20a determines the encryption key based on the result of majority voting of abnormal KI values ​​caused by the disturbance, resulting in an unintended switching of the encryption key from #1 to #2. 【0055】 As described above, in this embodiment, by providing the abnormality notification unit 23, the need for a second key exchange process in conventional standards is eliminated, and the time from resolving the disturbance to restoring to a normal encrypted communication state can be significantly reduced. 【0056】 The above description explains the operation of the encryption processing unit 10, the error notification unit 23, and the decryption processing unit 20a. However, the operation of the encryption processing unit 22 of the communication device 2a is the same as that of the encryption processing unit 10, the operation of the decryption processing unit 12a of the communication device 1a is the same as that of the decryption processing unit 20a, and the operation of the error notification unit 13 of the communication device 1a is the same as that of the error notification unit 23. 【0057】 The encryption processing unit 10, key generation unit 11, decryption processing unit 12a, and anomaly notification unit 13 of communication device 1a are implemented on the same integrated circuit (for example, a DSP (Digital Signal Processor) chip). Similarly, the decryption processing unit 20a, key generation unit 21, encryption processing unit 22, and anomaly notification unit 23 of communication device 2a are implemented on the same integrated circuit. [Explanation of symbols] 【0058】 1a, 2a... Communication device, 3... Network, 10, 22... Cryptography processing unit, 11, 21... Key generation unit, 12a, 20a... Decryption processing unit, 13, 23... Anomaly notification unit.

Claims

[Claim 1] A decryption processing unit configured to decrypt the ciphertext sent from the transmitting communication device, The device includes an abnormality notification unit configured to notify the decoding processing unit of the occurrence of an abnormality from the time an abnormality occurs in communication between the transmitting communication device and the device until the abnormality is resolved, The communication device is characterized in that the decoding processing unit maintains the decoding processing settings from before the notification while a notification is received from the abnormality notification unit. [Claim 2] In the communication device according to claim 1, The decryption processing unit is characterized in that it maintains the encryption key used before the notification while a notification is received from the abnormality notification unit. [Claim 3] In the communication device according to claim 2, The decryption processing unit, when there is no notification from the abnormality notification unit, determines the encryption key to be used by majority voting of encryption key index signals stored in multiple frame signals sent from the transmitting communication device, and when an encryption key switch occurs, initializes the encryption key that was used immediately before. [Claim 4] In the communication device according to claim 1, The decryption processing unit is characterized in that, while a notification is received from the abnormality notification unit, it maintains the type of encryption algorithm that was used before the notification. [Claim 5] In the communication device according to claim 4, The decryption processing unit is characterized in that, when there is no notification from the abnormality notification unit, it determines the type of encryption algorithm to be used by performing an equivalence determination process on encryption algorithm type signals stored in a plurality of frame signals sent from the transmitting communication device. [Claim 6] A decryption processing unit configured to decrypt the ciphertext sent from the transmitting communication device, The system includes an abnormality notification unit configured to notify the decoding processing unit of the occurrence of an abnormality from the time an abnormality occurs in communication between the transmitting communication device and the receiving communication device on which the chip is installed until the abnormality is resolved, The decoding processing unit is characterized in that it maintains the decoding processing settings from before the notification while a notification is received from the abnormality notification unit.

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