JP2000286833A - Communication system and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To re-synchronize a password even if password step-out occurs and to resume a password call without terminating the call by permitting a transmission side terminal to consider step-out to be password step-out and setting the transmission of synchronous pattern data in a reception terminal to be a password synchronous pattern re-transmission processing for re-synchronizing the password. SOLUTION: A transmission side terminal considers step-out to be password step-out and the transmission of synchronous pattern data in a reception terminal is a password synchronous pattern re-transmission processing for re- synchronizing a password. On a transmission side, a sound frame synchronism part 6 detects step-out, and a step-out detection signal 14 is outputted to a sound encoding part 1 and a password re-synchronism waiting timer 8 from the sound frame synchronism part 6 by the occurrence of equivalent password step-out and step-out is informed. When password step-out is recognized and the re-transmission processing of a password synchronous pattern for password re-synchronism is executed on a reception side, the reception side outputs password pattern data to a communication line 7 instead of sound encoding data which is transmitted till then.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system and a communication method for performing re-synchronization of ciphers in, for example, cipher (confidential) voice communication.

[0002]

2. Description of the Related Art In recent years, maintaining the confidentiality of communication has become an issue.
More demanding than ever, as a means to respond to it,
Various encryption methods (encryption algorithms) and devices using them have been proposed. These encryption methods include, for example, a method of synchronizing encryption and decryption, a method of storing a different encryption key for each communication partner, or a decryption key of the encryption key and the decryption key. There is a system where the secret is kept secret and the encryption key is made public.

FIG. 8 is a block diagram showing the configuration of a communication system employing a conventional encryption resynchronization method in an encrypted voice call. In the communication system shown in the figure, both the transmitting side and the receiving side include a speech encoding unit 1, an encryption unit 2, a line interface unit 3, a ciphertext unit 4, a speech decoding unit 5, and a speech frame synchronization unit 6. And a configuration in which they are connected via a communication line 7.

Next, the operation of the conventional communication system will be described. Basic encrypted voice communication is realized by the following procedure. That is, the voice coding unit 1 converts analog voice from a transmitter (not shown) into a digital signal to generate voice coded data. And the encryption unit 2
, The voice-encoded data is encrypted, and the encrypted data is transmitted to the other party through the line interface unit 3 and the communication line 7.

On the other hand, the receiver receives voice data transmitted from the transmitter via the line interface unit 3 and transmits the encrypted voice data to the encryption culture unit 4.
Return to plaintext. Then, the audio frame synchronization unit 6 establishes audio frame synchronization, and the audio decoding unit 5
The original analog voice is reproduced from the voice coded data and transmitted to a receiver (not shown).

[0006]

However, in a cipher call realized by the basic system of the above-mentioned conventional communication system, if the cipher synchronization is lost due to a malfunction such as a communication line failure or a bit slip during the call, for example, There is a problem that an error occurs in the plainly encoded voice encoded data, and analog voice different from the original voice is reproduced, which hinders communication.

In the cipher resynchronization method in the cipher voice communication according to the above conventional communication system, the encrypting unit on the transmitting side and the cipher decrypting unit on the receiving side resynchronize with each other when the cipher loses synchronization during the call. No measures have been taken. Therefore, for the above-mentioned trouble, the receiver must end the call for the line disconnection process and repeat the call start process from the beginning.

That is, in the cipher call according to the above-mentioned conventional cipher resynchronization method, once the cipher synchronization is lost,
There is a problem that the encrypted call cannot be resumed unless the line disconnection process due to the end of the call and the process for re-calling are executed.

For this reason, in the cipher resynchronization method in the above-mentioned conventional communication system, if a cipher loss occurs during a cipher call, the caller must be disconnected from the line (for example, the receiver goes on-hook) in order to recover the call. Etc.), and the call processing must be restarted from the beginning.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object the purpose of re-encryption even when the communication partner is out of synchronization and normal communication information cannot be reproduced. Even if the other device executes the process for synchronization (cryptographic synchronization pattern retransmission process) and does not end the communication,
An object of the present invention is to provide a communication system and a communication method capable of restarting encrypted communication.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for connecting terminals connected via a communication line.
A communication system for transmitting and receiving encrypted information, wherein at a transmitting terminal, means for detecting out-of-synchronization of the encrypted information, and when the out-of-sync is detected, a predetermined fixed Means for inserting pattern data, means for transmitting the information after insertion of the fixed pattern data to the receiving terminal, means for detecting the fixed pattern from the received information at the receiving terminal, and wherein the fixed pattern data is detected. Means for transmitting predetermined synchronization pattern data to the transmission-side terminal, the transmission-side terminal regards the out-of-synchronization as an out-of-synchronization for the information, and The transmission of the pattern data provides a communication system which is an encryption synchronization pattern retransmission process for encryption resynchronization.

Preferably, the transmitting terminal further comprises:
Means for measuring the time from transmitting the information after inserting the fixed pattern to the receiving terminal to establishing the cryptographic resynchronization, and, if the measured time exceeds a certain time, the receiving terminal Means for transmitting a cryptographic synchronization pattern.

[0013] Preferably, the insertion of the fixed pattern data is a process of replacing a frame bit of the information with a bit of a specific pattern.

[0014] Preferably, the system further comprises means for prompting a user of the communication system to resend the encryption synchronization pattern when the measured time exceeds a predetermined time. When the user performs a predetermined operation, the cipher synchronization pattern is retransmitted.

According to another aspect of the present invention, in a communication system for transmitting and receiving information between terminals connected via a communication line, a generating means for generating data in which the information is partially encrypted, and the data being out of synchronization Means for detecting the synchronization, when the out-of-synchronization is detected, means for detecting the synchronization establishment timing of the information, based on the synchronization establishment timing,
Means for correcting a bit position for cryptographic synchronization of the data, and providing a communication system for performing cryptographic resynchronization by correcting the bit position.

Preferably, the generation means encrypts a part other than the frame bits of the information.

According to another aspect of the present invention, in a communication method for transmitting and receiving encrypted information between terminals connected via a communication line, the transmitting terminal may be configured to remove the synchronization of the encrypted information. When the fixed pattern data is detected, the fixed pattern data is inserted into the information, and the information after the fixed pattern data is inserted is transmitted to the receiving terminal. When the receiving terminal detects the fixed pattern from the received information, To the transmitting terminal, the transmitting terminal regards the out-of-synchronization as an out-of-synchronization for the information, and the transmitting of the synchronizing pattern data in the Provided is a communication method which is a retransmission process of an encryption synchronization pattern for synchronization.

Preferably, the transmitting terminal further comprises:
The time after transmitting the information after the insertion of the fixed pattern to the receiving terminal and measuring the time from when the encryption resynchronization is established is measured, and when the measured time exceeds a certain time, the receiving terminal is Send the cryptographic synchronization pattern.

Preferably, the insertion of the fixed pattern data is a process of replacing a frame bit of the information with a bit of a specific pattern.

Preferably, the method further comprises a step of prompting a user of the communication system to resend the encryption synchronization pattern when the measured time exceeds a predetermined time. Then, when the user performs a predetermined operation, the cipher synchronization pattern is retransmitted.

Still another invention relates to a communication method for transmitting and receiving information between terminals connected via a communication line,
A generation step of generating data obtained by partially encrypting the information, a step of detecting an out-of-synchronization of the data, and a step of detecting a synchronization establishment timing of the information when the out-of-synchronism is detected; Correcting the bit position of the cryptographic synchronization of the data based on the synchronization establishment timing, and providing a communication method of performing cryptographic resynchronization by correcting the bit position.

Preferably, in the generating step, a portion other than the frame bits of the information is encrypted.

[0023]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of a communication system according to Embodiment 1 of the present invention. In the communication system shown in FIG. 1, both the transmitting side and the receiving side have a voice encoding unit 1, an encrypting unit 2, a line interface unit 3,
A ciphertext unit 4, a voice decoding unit 5, a voice frame synchronizing unit 6, a cryptographic resynchronization waiting timer unit 8, and a fixed pattern detecting unit 9, which communicate with each other via a communication line 7. Take.

Next, the operation of the communication system according to the present embodiment will be described. FIG. 2 and FIG. 3 are flowcharts showing procedures for cryptographic resynchronization in the communication system according to the present embodiment. Note that the flowchart of FIG. 2 shows a sequence on the side where the out-of-synchronization occurs, and FIG. 3 is a flowchart corresponding to the sequence on the other side.

In the communication system according to the present embodiment, if the cryptographic synchronization is lost during the cryptographic voice call due to the failure of the communication line 7 or the bit slip, the communication line 7 and the interface unit 3 are used. The data is received and sent to the ciphertext unit 4 to be returned to the plaintext. Here, the speech coded data returned to the plaintext becomes error data different from the original data due to the above-mentioned loss of synchronization. Therefore, if the synchronization is determined based on the error data, the audio frame synchronization unit 6 inevitably loses synchronization of the audio frame.

Therefore, in the communication system according to the present embodiment, as a basic principle, the above-described voice frame out-of-sync phenomenon is regarded as equivalent to the occurrence of cryptographic out-of-sync. According to this principle, when the audio frame synchronization unit 6 detects out-of-synchronization, the audio encoding unit 1 encodes the encoded audio data (for example, for one frame, but need not be fixed to one frame in particular). Instead of this, fixed pattern data for notifying the loss of encryption synchronization (this is referred to as an encryption synchronization pattern retransmission request) is transmitted to the line interface unit 3.
Via the communication line 7 to the other party. Note that, also in this case, the encryption unit 2 performs encryption of the transmission data.

That is, in the present communication system, FIG.
In step S21, the audio frame synchronizing unit 6 detects the loss of synchronization. In step S22, the audio frame synchronizing unit 6 determines that the synchronization loss has occurred equivalently. Out-of-synchronization detection signal 14 is output, and an out-of-synchronization notification is made.

Upon receiving the out-of-synchronization detection signal 14, the voice coding unit 1 determines in step S23 that a cryptographic synchronization pattern retransmission request (fixed pattern data) indicating a cryptographic resynchronization request is performed instead of the encoded voice data. Insert
Then, in the subsequent step S24, the encryption unit 2 encrypts the data including the pattern data and sends it to the other party via the line interface unit 3 and the communication line 7.

On the other hand, the other party communicates in step S3 of FIG.
In step S1, the fixed pattern data sent via the communication line 7 is received.
Divides the encrypted data. Then, in step S33, the audio frame synchronization unit 6 in the audio decoding unit 5 establishes audio frame synchronization.

In the following step S34, it is determined whether or not the fixed pattern data is detected by the fixed pattern detecting section 9. Here, when the fixed pattern is detected (YES in step S34), the receiving side recognizes that the data transmission side has lost the cryptographic synchronization, and the result is as follows.
The fixed pattern detection unit 9 sends the encrypted synchronization pattern retransmission request signal 13 to the encryption unit 2. Then, the encryption unit 2 performs a retransmission process of the encryption synchronization pattern for encryption resynchronization (step S35).

If no fixed pattern is detected in step S34 (N in step S34)
O), the encryption unit 2 determines that there is no
No retransmission processing of the cryptographic synchronization pattern is performed for cryptographic resynchronization (step S36).

As described above, when the receiving side performs the retransmission processing of the cryptographic synchronization pattern for the cryptographic resynchronization, the receiving side replaces the voice coded data that has been transmitted so far with the line interface unit. 3 to output the cryptographic synchronization pattern data to the communication line 7. As a result, encryption resynchronization is established, and encryption communication can be resumed.

The above example is based on the assumption that cryptographic synchronization has been established on the line that reports the loss of cryptographic synchronization. However, in both transmission and reception lines,
At the same time, when the synchronization is lost, encryption resynchronization cannot be realized only by the above processing.

Thus, the communication system according to the present embodiment has a cryptographic resynchronization wait timer 8 to measure the time from sending a fixed pattern to reestablishing cryptographic synchronization. That is, in step S25 of FIG.
An out-of-synchronization detection signal 14 is sent from the audio frame synchronization unit 6 in the audio decoding unit 5 to the encryption resynchronization wait timer 8,
The timer is started by this signal. Then, in the following step S26, it is determined whether or not the audio frame synchronization is re-established by the audio frame synchronization unit 6 within a fixed time (fixed timeout time).

If it is determined in step S26 that the voice frame synchronization has been re-established within a predetermined time, in step S27, it is equivalently detected that encryption re-synchronization has been established, and encryption communication is resumed. However, if the encryption resynchronization is not performed even after a certain time has elapsed (NO in step S26), the encryption resynchronization wait timer 8 generates a timeout signal 12 and sends it to the encryption unit 2. Then, it is equivalently recognized that the other party's line is also out of synchronization (step S28).

As a result of the above recognition, the cryptographic synchronization on both the transmitting and receiving sides is out of sync. Therefore, the cryptographic synchronization pattern is output to the communication line 7 through the line interface unit 3 and the cryptographic resynchronization on the communication partner side is established. I do. In addition,
The activation of the encryption resynchronization wait timer 8 is essentially the same whether triggered by the transmission of the fixed pattern as described above or the detection of the loss of synchronization of the audio frame. In the communication system according to the present embodiment shown in FIG. 1, detection of loss of synchronization of a voice frame is a trigger for starting the encryption resynchronization wait timer 8.

FIG. 4 is a diagram showing a configuration of a communication frame used in the communication system according to the present embodiment. As shown in the figure, in the communication frame according to the present embodiment, a fixed bit pattern 41 for audio frame synchronization is arranged at the head, followed by a fixed pattern data 42 for requesting retransmission of the encryption synchronization pattern. That is, the configuration is such that the fixed pattern data for requesting the retransmission of the cryptographic synchronization pattern is originally inserted into the portion where the audio encoded data is inserted.

As described above, according to the present embodiment, even when cryptographic synchronization is lost due to a communication line failure or bit slip during a cryptographic voice call, the cryptographic synchronization pattern is retransmitted. The cipher resynchronization can be established without disconnecting the call itself, and the cipher call can be easily resumed.

Further, according to the present embodiment, the timer is started after the fixed pattern data is transmitted, and it is determined whether or not the audio frame synchronization has been re-established within a certain period of time. Since the establishment of synchronization is detected, even if the out-of-synchronization occurs on both the transmitting and receiving lines, after a certain period of time, the re-synchronization of both is established and the encrypted communication can be resumed.

Embodiment 2 Hereinafter, Embodiment 2 of the present invention will be described. Since the communication system according to the present embodiment has the same configuration as the communication system according to the first embodiment shown in FIG. 1, illustration and description thereof are omitted here.

As described above, in the first embodiment, by replacing the voice coded data in the voice communication with the fixed pattern data for the cryptographic resynchronization request, the fact that the cryptographic synchronization is lost is notified to the other party. Notifying. However, the out-of-synchronization notification in the present invention is not limited to replacement with fixed pattern data, and it goes without saying that various modifications are possible.

As a method equivalent to the above notification, for example, the fixed bit pattern for synchronizing the audio frame of the audio encoded frame may be replaced with a specific bit pattern. That is, in the communication system according to the present embodiment, as shown in FIG. 5, a frame having a configuration in which a cryptographic synchronization pattern retransmission request fixed bit pattern 51 is inserted at the beginning, followed by audio encoded data 52. Is transmitted to the other party to notify the loss of synchronization. That is, the fixed bit pattern for requesting retransmission of the encryption synchronization pattern is originally inserted into the portion where the fixed bit pattern for audio frame synchronization is inserted.

As described above, in the present embodiment, instead of replacing the encoded voice data with the fixed pattern data for requesting the encryption resynchronization, the audio frame synchronization fixed bit pattern of the encoded audio frame is specified. By transmitting the bit pattern to the other party and notifying the other side of the out-of-sync, even if the out-of-synchronization occurs on both the transmitting and receiving lines, re-synchronization of both is established after a certain period of time Then, the encrypted call can be resumed.

Embodiment 3 FIG. Hereinafter, Embodiment 3 of the present invention will be described. FIG. 6 is a block diagram showing a configuration of the communication system according to the present embodiment. In the figure, the same components as those of the communication system according to Embodiment 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted here.

In the communication system according to the first embodiment, the encryption resynchronization wait timer unit 8 detects a resynchronization timeout and resends the encryption synchronization pattern. A method of retransmitting the cryptographic synchronization pattern regardless of the above is adopted. That is, in the communication system according to the present embodiment, the cipher synchronization pattern is retransmitted by a predetermined button operation by the caller.

In the communication system shown in FIG. 6, when the out-of-synchronization detection signal 14 is sent from the voice frame synchronization unit 6 to the encryption resynchronization wait timer 8, the timer 8 is started by this signal. Then, when a predetermined time has elapsed, the timeout display section 11 performs a display for prompting the caller to retransmit the encryption synchronization pattern by the timeout signal from the timer 8.

The caller sees the display on the time-out display section 11 and knows that the encryption synchronization has been lost in the two-way line, and is prompted to resend the encryption synchronization pattern, and presses the encryption synchronization pattern resend button 10. I do. As shown in FIG. 6, the encryption synchronization pattern resend button 10 is connected to the encryption unit 2, and when the encryption unit 2 detects that the button has been pressed, the encryption unit 2 transmits the encrypted synchronization pattern via the line interface unit 3. Retransmit the cryptographic synchronization pattern.

As described above, according to the present embodiment, the caller who knows the loss of synchronization by the display presses the encryption synchronization pattern resend button to resend the encryption synchronization pattern, so that the two parties are synchronized. Even if a disconnection has occurred, there is the effect that the cipher call can be surely restarted without interruption or call termination processing.

Embodiment 4 Hereinafter, Embodiment 4 of the present invention will be described. FIG. 7 is a block diagram showing a configuration of the communication system according to the present embodiment. In the communication system shown in the figure, the same components as those of the communication system according to the first embodiment shown in FIG.
The description is omitted.

In the first to third embodiments, the encryption unit 2
Since the entirety of the audio frame is encrypted and the out-of-synchronization occurs inevitably when the out-of-synchronization occurs, the basic principle of detecting out-of-synchronization based on the out-of-synchronization is adopted. However, in the present embodiment, as described below, as a method different from this basic principle, out-of-synchronization is detected without encrypting the entire voice frame.

In the communication system according to the present embodiment, only the fixed bit pattern portion for audio frame synchronization in the audio frame is not always encrypted, but is transmitted as plain data to the other party, and the audio encoded data is transmitted. The part is encrypted to ensure confidentiality of the call. That is, the present communication system performs encryption resynchronization using a frame in which an unencrypted part and an encrypted part are mixed in the same frame.

As shown in FIG. 7, in the communication system according to the present embodiment, as described above, only a specific portion in a voice frame is not always encrypted and can be received in the form of plain data. In order to maintain the audio frame synchronization irrespective of the state of the encryption synchronization, the audio decoding unit 5
Is the line interface unit 3 before the encryption flat culture unit 4
Is configured to receive the received data via the.

As described above, since the voice decoding unit 5 receives the received data before the plaintext unit 4, the voice frame synchronization unit 6 performs the voice frame synchronization for the voice frame in the voice frame sent from the other party. Only the fixed bit pattern part is
You can receive plain data. Then, the audio decoding unit 5 gives the encryption / decryption unit 4 a timing for detecting the fixed bit pattern for audio frame synchronization,
Output together with the encrypted audio data.

Therefore, the present communication system can correct the bit position of the cryptographic synchronization based on the establishment timing of the audio frame synchronization even when the cryptographic synchronization is lost, thereby enabling the cryptographic resynchronization.

As described above, according to the present embodiment, only the fixed bit pattern portion for audio frame synchronization in the audio frame is not encrypted at all times, but is transmitted as plain data to the other party. By encrypting and transmitting only the coded data part, even if the out-of-synchronization occurs, only the frame bit part can always be received in the form of plain data. Can resume.

Further, in the case of the communication system according to the present embodiment, in order to maintain synchronization by voice frame synchronization,
Basically, it is not necessary to transmit a fixed pattern as a request for retransmitting the cryptographic synchronization pattern to the other party.

In each of the above embodiments, the object to be transmitted / received while establishing synchronization is audio data. However, the type of data is not limited to this. For example, facsimile information, image information, computer data And so on, encryption communication can be performed in the same manner as voice data. In this case, in transmission and reception of various types of information, for example, a condition that a synchronization detection function is added by framing data is necessary.

[0058]

As described above, according to the present invention,
What is claimed is: 1. A communication system for transmitting and receiving encrypted information between terminals connected via a communication line, wherein a transmitting terminal detects a loss of synchronization of the encrypted information, Is detected, means for inserting predetermined fixed pattern data into the information, means for transmitting the information after the fixed pattern data is inserted to the receiving terminal, and the receiving terminal in the receiving terminal, the fixed pattern from the received information Means for detecting, and when the fixed pattern data is detected, means for transmitting predetermined synchronization pattern data to the transmission side terminal, wherein the transmission side terminal detects the out-of-synchronization as the crypto-synchronization for the information. The transmission of the synchronization pattern data in the receiving terminal is a communication system in which encryption synchronization pattern retransmission processing for encryption resynchronization is performed. By subjecting, perform a cryptographic resynchronization establishment without interrupting transmission and reception of information.

The transmitting terminal further includes means for measuring the time from when the information after the insertion of the fixed pattern is inserted to the receiving terminal to when the encryption resynchronization is established,
Means for transmitting an encryption synchronization pattern to the reception-side terminal when the measured time exceeds a predetermined time, so that even when encryption-out-of-synchronization occurs in both transmission and reception lines, After a certain period of time, the encryption re-synchronization between the two is established, and the transmission and reception of the encryption information can be resumed.

The insertion of the fixed pattern data is
By replacing the frame bits of the above information with bits of a specific pattern, even if the cryptosync is lost,
Encryption resynchronization can be established without interrupting transmission and reception of information.

Further, when the measured time exceeds a predetermined time, there is provided a means for prompting a user of the communication system to retransmit the encryption synchronization pattern. By performing the above operation, the above-mentioned cryptographic synchronization pattern is retransmitted,
Even when synchronization is lost in both cases, communication of encrypted information can be reliably resumed without interrupting or terminating the communication.

According to another aspect of the present invention, in a communication system for transmitting and receiving information between terminals connected via a communication line, a generating means for generating data obtained by partially encrypting the information, Means for detecting out-of-synchronization, means for detecting the synchronization establishment timing of the information when the out-of-synchronization is detected, and means for correcting the bit position of the cryptographic synchronization of the data based on the synchronization establishment timing And a communication system that performs encryption resynchronization by correcting the bit position is provided, so that communication of encrypted information can be resumed while maintaining synchronization of communication information.

Since the generating means encrypts a part other than the frame bits of the information, the non-encrypted part is always received as flat information.
You can re-synchronize the encryption.

Another aspect of the present invention is a communication method for transmitting and receiving encrypted information between terminals connected via a communication line, wherein the transmitting terminal removes the synchronization of the encrypted information. When the fixed pattern data is detected, the fixed pattern data is inserted into the information, and the information after the fixed pattern data is inserted is transmitted to the receiving terminal. When the receiving terminal detects the fixed pattern from the received information, To the transmitting terminal, the transmitting terminal regards the out-of-synchronization as an out-of-synchronization for the information, and the transmitting of the synchronizing pattern data in the By providing a communication method that is a process of retransmitting an encryption synchronization pattern for synchronization, it is possible to establish encryption resynchronization without interrupting transmission and reception of information.

Further, the transmitting terminal further measures the time from when the information after the insertion of the fixed pattern is inserted to the receiving terminal to when the encryption resynchronization is established, and the measured time is fixed. If the time is exceeded, the encryption synchronization pattern is transmitted to the above-mentioned receiving terminal. Once established, encryption information transmission / reception can be resumed.

The insertion of the fixed pattern data is as follows:
Since the process is a process of replacing the frame bits of the information with bits of a specific pattern, it is possible to establish cryptographic resynchronization without interrupting the transmission and reception of information even if the cryptographic synchronization is lost.

Further, the method further comprises a step of prompting the user of the communication system to retransmit the above-mentioned encryption synchronization pattern when the measured time exceeds a predetermined time. By performing the above operation, the encryption synchronization pattern is retransmitted, so that the communication of the encrypted information can be reliably resumed without interruption or termination of the communication even if the synchronization is lost.

According to still another aspect of the present invention, in a communication method for transmitting and receiving information between terminals connected via a communication line, a generating step of generating data obtained by partially encrypting the information; Detecting out of synchronization of the
Detecting the synchronization establishment timing of the information when the out-of-synchronization is detected, and correcting the bit position of the cryptographic synchronization of the data based on the synchronization establishment timing; Since the communication method for performing the encryption resynchronization by the correction is provided, the communication of the encrypted information can be restarted while maintaining the synchronization of the communication information.

Since the generation step encrypts a part other than the frame bits of the information, the non-encrypted part can be re-synchronized while always receiving plain information.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication system according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a flowchart showing a procedure for cryptographic resynchronization in the communication system according to the first embodiment, in particular, a sequence on a side where cryptographic out of synchronization has occurred.

FIG. 3 is a flowchart showing a procedure for cryptographic resynchronization in the communication system according to the first embodiment, particularly a sequence on a partner side on which synchronization loss has occurred;

FIG. 4 is a diagram showing a communication frame configuration used in the communication system according to the first embodiment.

FIG. 5 is a diagram showing a communication frame configuration used in a communication system according to Embodiment 2 of the present invention.

FIG. 6 is a block diagram showing a configuration of a communication system according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a communication system according to Embodiment 4 of the present invention.

FIG. 8 is a block diagram showing a configuration of a communication system employing a conventional cryptographic resynchronization method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Voice encoding part, 2 ... Encryption part, 3 ... Line interface part, 4 ... Encryption section, 5 ... Voice decoding part, 6 ... Voice frame synchronization part, 7 ... Communication line, 8 ... Encryption resynchronization Wait timer, 9: fixed pattern detection unit, 10: encryption synchronization pattern resend button, 11: timeout display unit

Claims (12)

[Claims] 1. Between terminals connected via a communication line,
A communication system for transmitting and receiving encrypted information, wherein at a transmitting terminal, means for detecting out-of-synchronization of the encrypted information, and when the out-of-synchronization is detected, a predetermined fixed Means for inserting pattern data, means for transmitting information after the fixed pattern data is inserted to a receiving terminal, means for detecting the fixed pattern from received information at the receiving terminal, and wherein the fixed pattern data is detected. Means for transmitting predetermined synchronization pattern data to the transmission-side terminal, the transmission-side terminal regards the out-of-synchronization as an out-of-synchronization of the information, and the synchronization in the reception-side terminal. The communication system according to claim 1, wherein the transmission of the pattern data is an encryption synchronization pattern retransmission process for encryption resynchronization. 2. The transmitting terminal further comprises: a unit for measuring a time from when the information after the insertion of the fixed pattern is inserted to the receiving terminal to when the cryptographic resynchronization is established; and the measured time. 2. A communication system according to claim 1, further comprising: means for transmitting an encryption synchronization pattern to the receiving terminal when the time exceeds a predetermined time. 3. The communication system according to claim 1, wherein the insertion of the fixed pattern data is a process of replacing a frame bit of the information with a bit of a specific pattern. 4. The communication system according to claim 1, further comprising: a display for prompting a user of the communication system to retransmit the encryption synchronization pattern when the measured time exceeds a predetermined time, based on the display. 3. The communication system according to claim 2, wherein the encryption synchronization pattern is retransmitted by a person performing a predetermined operation. 5. A communication system for transmitting and receiving information between terminals connected via a communication line, comprising: generating means for generating data in which the information is partially encrypted; and detecting out-of-synchronization of the data. Means, when the out-of-synchronization is detected, means for detecting synchronization establishment timing of the information, and means for correcting a bit position of cryptographic synchronization of the data based on the synchronization establishment timing, A communication system for performing cryptographic resynchronization by correcting a bit position. 6. The information processing apparatus according to claim 5, wherein the generation unit encrypts a part of the information other than frame bits.
A communication system as described. 7. Between terminals connected via a communication line,
In a communication method for transmitting and receiving encrypted information, the transmitting terminal, when detecting out-of-synchronization of the encrypted information, inserts predetermined fixed pattern data into the information and inserts the fixed pattern data. When the fixed information is detected from the received information, the receiving terminal transmits predetermined synchronization pattern data to the transmitting terminal, and the transmitting terminal loses synchronization. Is regarded as out-of-synchronization of the information, and the transmission of the synchronization pattern data in the receiving terminal is a retransmission processing of an encryption synchronization pattern for encryption resynchronization. 8. The transmitting terminal further measures a time from when the information after the insertion of the fixed pattern is transmitted to the receiving terminal to when the cryptographic resynchronization is established, and the measured time is fixed. 8. The communication method according to claim 7, further comprising transmitting an encryption synchronization pattern to the receiving terminal when the time has elapsed. 9. The communication method according to claim 7, wherein the insertion of the fixed pattern data is a process of replacing a frame bit of the information with a bit of a specific pattern. 10. The method according to claim 1, further comprising a step of, when the measured time exceeds a predetermined time, displaying a message prompting a user of the communication system to retransmit the encryption synchronization pattern. 8. The communication method according to claim 7, wherein the encryption synchronization pattern is retransmitted by a person performing a predetermined operation. 11. A communication method for transmitting and receiving information between terminals connected via a communication line, wherein: a generating step of generating data in which the information is partially encrypted; and detecting a loss of synchronization of the data. A step of detecting the synchronization establishment timing of the information when the out-of-synchronization is detected; and correcting a bit position of the cryptographic synchronization of the data based on the synchronization establishment timing, A communication method characterized by performing cryptographic resynchronization by correcting a bit position. 12. The communication method according to claim 11, wherein said generating step encrypts a part other than a frame bit of said information.