JP2008286965A - Encryption apparatus for stream encryption, decryption apparatus for stream encryption, encryption apparatus for self-synchronized stream encryption, decryption apparatus for self-synchronized stream encryption, encryption method for stream encryption, encryption method for self-synchronized stream encryption and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To output a key sequence of arbitrary length, and to control adequate security level in accordance with the length of the key sequence to be output. <P>SOLUTION: An encryption apparatus for stream encryption includes: an internal state renewing function which generates an initial key and an initial vector and renews the internal state when a key sequence is output; an internal state memory means which memorizes the internal state output from the internal state renewing function; a key sequence generating function which reads the internal state memorized in the internal state memory means and outputs the key sequence; and an exclusive OR computing element which outputs a ciphertext by performing an exclusive OR operation of the key sequence output from the key sequence generating function and an input plaintext. The key sequence generating function is constituted by linking the arbitrary number of preprocessing blocks and function blocks. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stream cipher encryption apparatus, a stream cipher decryption apparatus, a self-synchronization stream cipher encryption apparatus, a self-synchronization stream cipher decryption apparatus, a stream cipher encryption method, and a self-synchronization stream cipher. The present invention relates to an encryption method and a program.

  In recent years, various services using computers have been provided due to the remarkable spread of the Internet. Many of the services provided in this way use encryption to conceal the communication contents. Here, as the encryption method, a common key encryption method in which encryption and decryption are performed with one key is common, but this common key encryption method is roughly divided into a block encryption method and a stream encryption method. Is done.

The stream encryption method can be expected to be processed at a higher speed than the block encryption method, and has recently attracted attention as a method for transmitting large-capacity data such as movies. An example of a method and apparatus for generating the described stream cipher is disclosed in Patent Document 1 below.
Special Table 2002-536912

  However, since the conventional stream cipher can output only a fixed-length key sequence, the processing load cannot be optimized. Further, even if a configuration for outputting an arbitrary length key sequence is constructed, there is no such thing as controlling the security level corresponding to the length of the output key sequence.

  Therefore, the present invention has been made in view of the above-described problems, and it is possible to output a stream cipher that can output an arbitrary-length key sequence and can control an appropriate security level according to the length of the output key sequence. Device, stream cipher decryption device, self-synchronization stream cipher encryption device, self-synchronization stream cipher decryption device, stream cipher encryption method, self-synchronization stream cipher encryption method and program The purpose is to do.

The present invention proposes the following items in order to solve the above problems.
(1) The present invention is a stream cipher encryption apparatus that inputs plaintext and outputs ciphertext, and generates an initial key and an initial vector and updates an internal state when a key sequence is output. A function (for example, equivalent to the internal state update function 11 in FIG. 1), and an internal state storage means for storing the internal state output from the internal state update function (for example, equivalent to the internal state storage memory 12 in FIG. 1); A key sequence generation function that reads the internal state stored in the internal state storage means and outputs a key sequence (for example, equivalent to the key sequence generation function 10 of FIG. 1), and is output from the key sequence generation function An exclusive OR calculator (for example, the exclusive OR calculators 17a, 17b, 17c,... In FIG. 1) that executes an exclusive OR operation between the key sequence and the input plaintext and outputs a ciphertext. Equivalent to 17n) The key sequence generation function includes: a first adder that outputs an addition value of a value of the first internal memory and a value output from the internal state storage means; and the first adder A first nonlinear function for nonlinearly processing the output value, a third internal memory for storing a value from the first nonlinear function, a value in the second internal memory, and the internal state storage means A second adder that outputs a value added to the second adder, a second non-linear function that performs non-linear processing on the value output from the second adder, and a value from the second non-linear function A first exclusive OR operation that executes an exclusive OR operation between the value of the fourth internal memory and the value of the first internal memory and the value output from the internal state storage means to output a key sequence; A value of the second internal memory and a value output from the internal state storage means A second exclusive OR calculator that executes an exclusive OR operation and outputs a key sequence; and an exclusive OR of the value of the third internal memory and the value output from the internal state storage means A third exclusive OR calculator that executes an operation and outputs a key sequence; and performs an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means A stream cipher encryption apparatus comprising: a fourth exclusive OR calculator that outputs a key sequence; and a predetermined number of units connected in accordance with the length of the key sequence that outputs a function unit. is suggesting.

  According to the present invention, the internal state update function generates an initial key and an initial vector, updates the internal state when the key sequence is output, and the internal state storage means stores the internal state output from the internal state update function. And the key sequence generation function reads the internal state stored in the internal state storage means, outputs the key sequence, and the exclusive OR calculator outputs the key sequence output from the key sequence generation function and the input The ciphertext is output by executing an exclusive OR operation with the plaintext. Then, a predetermined number of key sequence generation functions are connected according to the length of the key sequence that outputs the function unit. Therefore, a key sequence having an arbitrary multiple of the word length can be generated at a time, and an appropriate security level can be controlled according to the number of function units to be connected.

  (2) In the stream cipher encryption apparatus according to (1), the key sequence generation function includes an adder, a nonlinear function for nonlinearly processing the output of the adder, and a value from the nonlinear function. A stream cipher encryption apparatus is proposed in which a predetermined number of preprocessing units each including an internal memory to be stored are further connected in front of the function unit.

  According to this invention, the key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. A predetermined number is connected in front of the. Therefore, even when the length of the key sequence to be output is short, an appropriate security level can be controlled by arranging a predetermined number of preprocessing units before the function unit.

  (3) The present invention is a stream cipher encryption method using the stream cipher encryption device according to (1) or (2), wherein a first step of reading an initial key and an initial vector into an internal state memory ( For example, it corresponds to step S101 in FIG. 2), a second step (for example, corresponding to step S102 in FIG. 2) of stirring the internal state memory by the initial stirring process, and the key sequence generation function is the value of the internal state memory. A third step (for example, corresponding to step S103 in FIG. 2), a fourth step for updating the internal state memory (for example, corresponding to step S105 in FIG. 2), and the output And a fifth step (for example, corresponding to step S104 in FIG. 2) for outputting a ciphertext by exclusive OR operation of the key sequence and the plaintext. It has proposed an encryption method of over-time encryption.

  According to the present invention, using the encryption device for stream cipher (1) or (2), first, the initial key and the initial vector are read into the internal state memory, and the internal state memory is stirred by the initial stirring process. A sequence generation function reads the value of the internal state memory and outputs a key sequence. Then, the internal state memory is updated, and the ciphertext is output by an exclusive OR operation between the output key sequence and the plaintext. Therefore, it is possible to collectively generate a key sequence having an arbitrary multiple of the word length while maintaining an appropriate security level.

  (4) The present invention is a program for causing a computer to execute a stream cipher encryption method using the stream cipher encryption device according to (1) or (2), wherein an initial key and an initial vector are stored in an internal state. A first step (for example, corresponding to step S101 in FIG. 2) to be read into the memory, a second step (for example, corresponding to step S102 in FIG. 2) for stirring the internal state memory by the initial stirring process, and a key sequence generation The function reads a value in the internal state memory and outputs a key sequence (for example, corresponding to step S103 in FIG. 2), and a fourth step for updating the internal state memory (for example, step in FIG. 2) And a fifth step (for example, step S10 in FIG. 2) for outputting a ciphertext by exclusive OR operation of the output key sequence and plaintext. We propose a program for executing a corresponding) to the computer.

  According to the present invention, using the encryption device for stream cipher (1) or (2), first, the initial key and the initial vector are read into the internal state memory, and the internal state memory is stirred by the initial stirring process. A sequence generation function reads the value of the internal state memory and outputs a key sequence. Then, the internal state memory is updated, and the ciphertext is output by an exclusive OR operation between the output key sequence and the plaintext. Therefore, it is possible to collectively generate a key sequence having an arbitrary multiple of the word length while maintaining an appropriate security level.

  (5) A stream cipher decryption device that inputs ciphertext and outputs plaintext, generates an initial key and an initial vector, and updates an internal state when a key sequence is output (for example, 3) (corresponding to the internal state update function 11 in FIG. 3), internal state storage means for storing the internal state output from the internal state update function (for example, corresponding to the internal state storage memory 12 in FIG. 3), and the internal state A key sequence generation function (for example, corresponding to the key sequence generation function 10 in FIG. 3) that reads the internal state stored in the storage means and outputs a key sequence, the key sequence output from the key sequence generation function, and An exclusive OR calculator (for example, equivalent to the exclusive OR calculators 18a, 18b, 18c,..., 18n in FIG. 3) that executes an exclusive OR operation with the input ciphertext and outputs a plaintext. ), And The key sequence generation function outputs a first adder that outputs an addition value of a value in the first internal memory and a value output from the internal state storage means, and a value output from the first adder A first nonlinear function that performs nonlinear processing, a third internal memory that stores a value from the first nonlinear function, a value in the second internal memory, and a value output from the internal state storage means A second adder for outputting an added value; a second nonlinear function for nonlinearly processing the value output from the second adder; and a fourth internal for storing a value from the second nonlinear function A first exclusive OR calculator that executes an exclusive OR operation between a value of the first internal memory and a value output from the internal state storage means and outputs a key sequence; Exclusive theory between the value of the second internal memory and the value output from the internal state storage means A second exclusive OR operator that executes a sum operation and outputs a key sequence, and performs an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means A key sequence by executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means. Proposing a decryption apparatus for stream ciphers, wherein a predetermined number of units are connected according to the length of a key sequence for outputting a function unit comprising a fourth exclusive OR operator that outputs Yes.

  According to the present invention, the internal state update function generates an initial key and an initial vector, updates the internal state when the key sequence is output, and the internal state storage means stores the internal state output from the internal state update function. And the key sequence generation function reads the internal state stored in the internal state storage means, outputs the key sequence, and the exclusive OR calculator outputs the key sequence output from the key sequence generation function and the input A plain text is output by executing an exclusive OR operation with the cipher text. Then, a predetermined number of key sequence generation functions are connected according to the length of the key sequence that outputs the function unit. Therefore, it is possible to decrypt a ciphertext composed of an arbitrary-length key sequence while maintaining an appropriate security level.

  (6) In the stream cipher decryption device according to (5), the key sequence generation function includes an adder, a nonlinear function for nonlinearly processing the output of the adder, and a value from the nonlinear function. A stream cipher decryption apparatus is proposed in which a predetermined number of preprocessing units each including an internal memory for storage are further connected in front of the function unit.

  According to this invention, the key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. A predetermined number is connected in front of the. Therefore, even in the case of a ciphertext having a short key sequence to be output, it is possible to perform decryption while maintaining an appropriate security level by arranging a predetermined number of preprocessing units in front of the function unit.

  (7) The present invention is a self-synchronous stream cipher encryption device that inputs plaintext, outputs ciphertext, and feeds back the ciphertext to the input, and generates an extended key by inputting an initial value. A key expansion function (for example, corresponding to the key expansion function 21 in FIG. 5), expansion key storage means (for example, corresponding to the expansion key storage memory 22 in FIG. 5) for storing the generated expansion key, and the expansion A key sequence generation function (for example, corresponding to the key sequence generation function 20 of FIG. 5) that reads the expanded key stored in the key storage means and the previously encrypted ciphertext or initial vector and outputs a key sequence; An exclusive OR calculator (for example, the exclusive OR calculator 27a in FIG. 5) that executes an exclusive OR operation between the key sequence output from the sequence generation function and the input plaintext and outputs a ciphertext. 27b, 27c, ..., 27n And a compression function (for example, equivalent to the compression function 28 in FIG. 5) that compresses the output ciphertext and feeds back to the key sequence generation function. A first adder that outputs an added value of a value of one internal memory and a value output from the internal state storage means, and a first nonlinear that performs a non-linear process on the value output from the first adder A function, a third internal memory that stores a value from the first nonlinear function, and a second internal memory that outputs an addition value of the value of the second internal memory and the value output from the internal state storage means An adder, a second non-linear function for non-linearly processing the value output from the second adder, a fourth internal memory for storing a value from the second non-linear function, and the first internal Exclusive theory between the value of the memory and the value output from the internal state storage means Executes an exclusive OR operation between the value of the second internal memory and the value output from the internal state storage means, executing a sum operation and outputting a key sequence A key sequence by executing an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means. And a third exclusive OR calculator that outputs a key sequence by executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means. A self-synchronous stream cipher encrypting device is proposed in which a predetermined number of four OR circuits are connected in accordance with the length of a key sequence that outputs a function unit. .

  According to the present invention, the key expansion function inputs an initial value and generates an expanded key, and the expanded key storage means stores the generated expanded key. The key sequence generation function reads the expanded key stored in the expanded key storage unit and the previously encrypted ciphertext or initial vector, and outputs the key sequence. The exclusive OR calculator performs an exclusive OR operation between the key sequence output from the key sequence generation function and the input plaintext, and outputs a ciphertext. Then, the compression function compresses the output ciphertext and feeds it back to the key sequence generation function. Further, a predetermined number of key sequence generation functions are connected according to the length of the key sequence that outputs the function unit. Therefore, a key sequence having an arbitrary multiple of the word length can be generated in a batch, and an appropriate security level can be controlled according to the number of function units to be connected.

  (8) In the self-synchronous stream cipher encryption device according to (7), the key sequence generation function includes an adder, a non-linear function that performs non-linear processing on an output of the adder, and the non-linear function. A self-synchronous stream cipher encryption apparatus is proposed in which a predetermined number of preprocessing units each including an internal memory for storing the value of the above is further connected in front of the function unit.

  According to this invention, the key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. A predetermined number is connected in front of the. Therefore, even when the length of the key sequence to be output is short, an appropriate security level can be controlled by arranging a predetermined number of preprocessing units before the function unit.

  (9) The present invention is a stream cipher encryption method using the stream cipher self-synchronous encryption apparatus according to (7) or (8), wherein the initial key is expanded by a key expansion function and expanded. A first step (for example, corresponding to step S301 in FIG. 6) for setting the key as a key, and the key sequence generation function read the expanded key and the previously encrypted ciphertext or initial vector, and output the key sequence. A second step (for example, corresponding to step S302 in FIG. 6) and a third step (for example, the step in FIG. 6) for outputting the ciphertext by performing an exclusive OR operation between the key sequence and the plaintext. And a fourth step (for example, equivalent to step S303 in FIG. 6) for feeding back the output ciphertext and inputting it to the key generation function. It has proposed a method of encrypting unencrypted.

  According to this invention, using the self-synchronous encryption device for stream cipher described in (7) or (8), first, the initial key is expanded with the key expansion function, set as an expanded key in the memory, and the key The sequence generation function reads the expanded key and the previously encrypted ciphertext or initial vector, outputs the key sequence, and executes the exclusive OR operation between the key sequence and the plaintext, thereby outputting the ciphertext. The output ciphertext is fed back and input to the key generation function. Therefore, it is possible to collectively generate a key sequence having an arbitrary multiple of the word length while maintaining an appropriate security level.

  (10) The present invention is a program for causing a computer to execute a stream cipher encryption method using the stream cipher self-synchronizing encryption apparatus according to (7) or (8), A first step (for example, corresponding to step S301 in FIG. 6) that is expanded by the key expansion function and set in the memory as the expanded key, and the key sequence generation function includes the expanded key and the previously encrypted ciphertext or initial vector A second step (for example, corresponding to step S302 of FIG. 6) that reads the key sequence and outputs a ciphertext by executing an exclusive OR operation between the key sequence and the plaintext. Step (e.g., corresponding to step S303 in FIG. 6) and a fourth step (e.g., step S30 in FIG. 6) for feeding back the output ciphertext and inputting it to the key generation function Program for executing a corresponding) to, to the computer.

  According to this invention, using the self-synchronous encryption device for stream cipher described in (7) or (8), first, the initial key is expanded with the key expansion function, set as an expanded key in the memory, and the key The sequence generation function reads the expanded key and the previously encrypted ciphertext or initial vector, outputs the key sequence, and executes the exclusive OR operation between the key sequence and the plaintext, thereby outputting the ciphertext. The output ciphertext is fed back and input to the key generation function. Therefore, it is possible to collectively generate a key sequence having an arbitrary multiple of the word length while maintaining an appropriate security level.

  (11) The present invention is a self-synchronous stream cipher decryption device that inputs ciphertext and outputs plaintext, and receives an initial value and generates a key expansion function (for example, FIG. 7). Key expansion function 21), an expanded key storage means for storing the generated expanded key (for example, equivalent to the expanded key storage memory 22 in FIG. 7), and an expanded key stored in the expanded key storage means A key sequence generation function (for example, corresponding to the key sequence generation function 20 in FIG. 7) that reads a plaintext or initial vector decrypted last time and outputs a key sequence, and a key sequence output from the key sequence generation function An exclusive OR calculator (for example, the exclusive OR calculators 29a, 29b, 29c,..., 29n in FIG. 7) that executes an exclusive OR operation with the input ciphertext and outputs a plaintext. Equivalent)) and the output plaintext is compressed before A compression function that feeds back to the key sequence generation function (for example, corresponding to the compression function 30 in FIG. 7), and the key sequence generation function is output from the value of the first internal memory and the internal state storage means A first adder that outputs an addition value to the value, a first nonlinear function that performs nonlinear processing on the value output from the first adder, and a first adder that stores a value from the first nonlinear function 3, a second adder that outputs an addition value of the value of the second internal memory and the value output from the internal state storage means, and the value output from the second adder. A second nonlinear function for nonlinear processing; a fourth internal memory for storing a value from the second nonlinear function; a value of the first internal memory; and a value output from the internal state storage means A first exclusive that performs an exclusive OR operation and outputs a key sequence A logical sum calculator, and a second exclusive OR calculator that executes an exclusive OR operation between the value of the second internal memory and the value output from the internal state storage means and outputs a key sequence A third exclusive OR calculator that executes an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means, and outputs a key sequence, and A function unit comprising: a fourth exclusive OR calculator that executes an exclusive OR operation between the value of the internal memory 4 and the value output from the internal state storage means and outputs a key sequence A self-synchronous stream cipher decryption device is proposed in which a predetermined number of key sequences are concatenated according to the length of the key sequence.

  According to the present invention, the key expansion function receives an initial value and generates an expanded key. The expanded key storage unit stores the generated expanded key. The key sequence generation function reads the expanded key stored in the expanded key storage means and the plaintext or initial vector decrypted last time, outputs the key sequence, and the exclusive OR operator outputs from the key sequence generation function A plaintext is output by performing an exclusive OR operation of the input key sequence and the input ciphertext. Then, the compression function compresses the output plaintext and feeds it back to the key sequence generation function. Further, a predetermined number of key sequence generation functions are connected according to the length of the key sequence that outputs the function unit. Therefore, it is possible to decrypt a ciphertext composed of an arbitrary-length key sequence while maintaining an appropriate security level.

  (12) In the self-synchronous stream cipher decryption device according to (11), the key sequence generation function includes an adder, a nonlinear function for nonlinearly processing the output of the adder, and the nonlinear function. A self-synchronous stream cipher decryption apparatus is proposed in which a predetermined number of preprocessing units each including an internal memory for storing the value of the above are further connected in front of the function unit.

  According to this invention, the key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. A predetermined number is connected in front of the. Therefore, even in the case of a ciphertext having a short key sequence to be output, it is possible to perform decryption while maintaining an appropriate security level by arranging a predetermined number of preprocessing units in front of the function unit.

  According to the present invention, by providing flexibility in the configuration, there is an effect that a key sequence having an arbitrary multiple of the word length can be collectively generated while maintaining a security level appropriately. Further, according to the present invention, there is an effect that a ciphertext composed of a key sequence having an arbitrary multiple of the word length can be decrypted while maintaining an appropriate security level.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements and the like, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 1 to 4.

<Configuration of encryption device>
As shown in FIG. 1, the encryption apparatus according to the first embodiment includes a key sequence generation function 10, an internal state update function 11, an internal state storage memory 12, and exclusive OR calculators 17a, 17b, 17c,..., 17n. The key sequence generation function 10 includes an arbitrary number of preprocessing blocks and function blocks. The preprocessing block includes, for example, an adder 13a, a nonlinear function 14a, and an internal memory 15a. The block includes internal memories 15c to 15f, adders 13d and 13e, nonlinear functions 14c and 14d, and exclusive OR calculators 16a to 16d.

  Here, the internal state update function 11 generates an initial key and an initial vector, and updates the internal state when the key sequence is output. The internal state storage memory 12 stores the internal state output from the internal state update function 11. The key sequence generation function 10 reads the internal state stored in the internal state storage memory 12 and outputs a key sequence. The exclusive OR calculators 17a, 17b, 17c,..., 17n execute an exclusive OR operation between the key sequence output from the key sequence generation function 10 and the input plaintext, and output a ciphertext. .

  Further, the adder 13 d constituting the function block forming a part of the key sequence generation function 10 outputs an addition value of the value of the internal memory 15 c and the value output from the internal state storage memory 12. The nonlinear function 14d performs nonlinear processing on the value output from the adder 13d. The internal memory 15f stores a value from the nonlinear function 14d. The adder 13e outputs an addition value between the value in the internal memory 15e and the value output from the internal state storage memory 12. The nonlinear function 14c performs nonlinear processing on the value output from the adder 13e. The internal memory 15d stores a value from the nonlinear function 14c. The exclusive OR calculator 16a executes an exclusive OR operation between the value of the internal memory 15c and the value output from the internal state storage memory 12, and outputs a key sequence. The exclusive OR calculator 16d performs an exclusive OR operation on the value of the internal memory 15f and the value output from the internal state storage memory 12, and outputs a key sequence. The exclusive OR calculator 16c performs an exclusive OR operation on the value of the internal memory 15e and the value output from the internal state storage memory 12, and outputs a key sequence. The exclusive OR operator performs an exclusive OR operation on the value of the internal memory 15d and the value output from the internal state storage memory 12, and outputs a key sequence.

  By concatenating a predetermined number of function blocks having the above-described configuration, a key sequence having an arbitrary multiple of the word length can be collectively generated. Further, since the frequency in which the value in the key generation function passes through the nonlinear function increases according to the number of function units to be connected, an appropriate security level can be controlled.

  Further, the adder 13a constituting the preprocessing block forming a part of the key sequence generation function 10 executes, for example, an addition process between the value of the internal memory and the value stored in the internal state storage memory 12. The nonlinear function 14a performs nonlinear processing on the output of the adder 13a. The internal memory 15a stores a value obtained by performing nonlinear processing on the nonlinear function 14a.

  By connecting a predetermined number of preprocessing blocks having the above configuration before the function block, the frequency of the value in the key generation function passing through the nonlinear function can be increased even when the key sequence is short. Appropriate security level can be controlled.

<Encryption processing>
An encryption process using the encryption apparatus according to the present embodiment will be described with reference to FIG.
First, an initial key and an initial vector are read into the internal state storage memory 12 (step S101). Next, the inside of the internal state storage memory 12 is stirred by the initial stirring process (step 102). The key sequence generation function 10 reads the value in the internal state storage memory 12 and outputs the key sequence (step S103). At this time, the value of the internal state storage memory 12 is updated (step S105), the process returns to step S101, and the key sequence and plaintext output from the key sequence generation function 10 are obtained by the exclusive OR calculators 17a to 17n. The exclusive OR operation is performed to output a ciphertext (step S104).

  Therefore, according to the encryption apparatus according to the present embodiment, it is possible to collectively generate a key sequence having an arbitrary multiple of the word length while maintaining an appropriate security level.

<Configuration of Decoding Device>
As shown in FIG. 3, the decryption device corresponding to the encryption device includes a key sequence generation function 10, an internal state update function 11, an internal state storage memory 12, and exclusive OR calculators 18a and 18b. , 18c,..., 18n. The key sequence generation function 10 includes an arbitrary number of preprocessing blocks and function blocks. The preprocessing block includes, for example, an adder 13a, a nonlinear function 14a, and an internal memory 15a. The block includes internal memories 15c to 15f, adders 13d and 13e, nonlinear functions 14c and 14d, and exclusive OR calculators 16a to 16d. In addition, since the component which attaches | subjects the same code | symbol as said encryption apparatus has the same function, the detailed description is abbreviate | omitted.

  The exclusive OR calculators 18a, 18b, 18c,..., 18n execute an exclusive OR operation between the key sequence output from the key sequence generation function 10 and the input ciphertext and output plaintext. .

  Therefore, in the decryption device according to the present embodiment, it is possible to decrypt a ciphertext composed of an arbitrary-length key sequence while maintaining an appropriate security level. Even in the case of ciphertext having a short key sequence to be output, it is possible to perform decryption while maintaining an appropriate security level by arranging a predetermined number of preprocessing units in the preceding stage of the function unit.

<Decryption process>
Decoding processing using the decoding apparatus according to the present embodiment will be described with reference to FIG.
First, an initial key and an initial vector are read into the internal state storage memory 12 (step S201). Next, the inside of the internal state storage memory 12 is stirred by the initial stirring process (step 202). The key sequence generation function 10 reads the value of the internal state storage memory 12 and outputs the key sequence (step S203). At this time, the value of the internal state storage memory 12 is updated (step S205), the process returns to step S101, and the key sequence and ciphertext output from the key sequence generation function 10 are exclusive OR calculators 18a to 18n. To output a plain text by performing an exclusive OR operation (step S204).

  Therefore, according to the decryption apparatus according to the present embodiment, it is possible to decrypt a ciphertext composed of an arbitrary-length key sequence while maintaining an appropriate security level.

<Second Embodiment>
Next, a second embodiment will be described with reference to FIGS.

<Configuration of self-synchronous encryption device>
As shown in FIG. 5, the self-synchronous encryption apparatus according to the second embodiment includes a key sequence generation function 20, a key expansion function 21, an extended key storage memory 22, an exclusive OR calculator 27a, 27b, 27c,..., 27n, and a compression function 28. The key sequence generation function 20 includes an arbitrary number of preprocessing blocks and function blocks. The preprocessing block includes, for example, an adder 23a, a nonlinear function 24a, and an internal memory 25a. The block includes internal memories 25c to 25f, adders 23d and 23e, nonlinear functions 24c and 24d, and exclusive OR calculators 26a to 26d. Note that the internal configuration of the key sequence generation function 20 is the same as that of the first embodiment, and thus detailed description thereof is omitted.

  Here, the key expansion function 21 inputs an initial value and generates an expanded key. The extended key storage memory 22 stores the generated extended key. The key sequence generation function 20 reads the expanded key stored in the expanded key storage memory 22 and the previously encrypted ciphertext or initial vector, and outputs the key sequence. The exclusive OR calculators 27a, 27b, 27c,..., 27n execute an exclusive OR operation between the key sequence output from the key sequence generation function 20 and the input plaintext, and output a ciphertext. . The compression function 28 compresses the output ciphertext and feeds it back to the key sequence generation function 20.

<Encryption processing of self-synchronous encryption device>
The encryption process of the self-synchronous encryption apparatus according to the second embodiment will be described with reference to FIG.
First, the initial key is expanded by the key expansion function 21, and set as an expanded key in the expanded key storage memory 22 (step S301). The key sequence generation function 20 reads the expanded key set in the expanded key storage memory 22 and the previously encrypted ciphertext or initial vector, and outputs the key sequence (step S302). Then, by executing an exclusive OR operation between the output key sequence and plaintext, the ciphertext is output, and the output ciphertext is fed back via the compression function 28 and input to the key sequence generation function 20. (Step S303).

  Therefore, in the self-synchronous encryption apparatus according to the present embodiment, a key sequence having an arbitrary multiple of the word length can be generated at a time, and an appropriate security level can be controlled according to the number of function units to be connected. Can do. Even when the length of the key sequence to be output is short, an appropriate security level can be controlled by arranging a predetermined number of preprocessing units before the function unit.

<Configuration of self-synchronous decoding device>
As shown in FIG. 7, the self-synchronous decoding device according to the second embodiment includes a key sequence generation function 20, a key expansion function 21, an extended key storage memory 22, an exclusive OR calculator 29a, 29b, 29c,..., 29n, and a compression function 30. The key sequence generation function 20 includes an arbitrary number of preprocessing blocks and function blocks. The preprocessing block includes, for example, an adder 23a, a nonlinear function 24a, and an internal memory 25a. The block includes internal memories 25c to 25f, adders 23d and 23e, nonlinear functions 24c and 24d, and exclusive OR calculators 26a to 26d. Note that the internal configuration of the key sequence generation function 20 is the same as that of the self-synchronous encryption apparatus described above, and detailed description thereof is omitted.

  Here, the exclusive OR calculators 29a, 29b, 29c,..., 29n execute an exclusive OR operation between the key sequence output from the key sequence generation function 20 and the input ciphertext and execute plaintext. Is output. The compression function 30 compresses the output plaintext and feeds it back to the key sequence generation function 20.

<Decoding process of self-synchronous decoding device>
The decoding process of the self-synchronous decoding device according to the second embodiment will be described with reference to FIG.
First, the initial key is expanded by the key expansion function 21, and set as an expanded key in the expanded key storage memory 22 (step S401). The key sequence generation function 20 reads the expanded key set in the expanded key storage memory 22 and the plaintext or initial vector decrypted last time and outputs the key sequence (step S402). Then, by executing an exclusive OR operation between the output key sequence and the ciphertext, the plaintext is output, and the output plaintext is fed back via the compression function 30 and input to the key sequence generation function 20 ( Step S403).

  Therefore, in the self-synchronous decryption device according to the present embodiment, it is possible to decrypt a ciphertext composed of an arbitrary-length key sequence while maintaining an appropriate security level. Even in the case of ciphertext having a short key sequence to be output, it is possible to perform decryption while maintaining an appropriate security level by arranging a predetermined number of preprocessing units in the preceding stage of the function unit.

  Note that the above-described series of processing is recorded as a program on a computer-readable recording medium, and the program recorded on the recording medium is stored in a stream cipher encryption apparatus, decryption apparatus, self-synchronization encryption apparatus, and self-synchronization type. The stream cipher encryption device, the decryption device self-synchronization encryption device, and the self-synchronization decryption device of the present invention can be realized by being read and executed by the decryption device.

  In addition, if a WWW (World Wide Web) system is used, a homepage providing environment (or display environment) is also included. Further, the program may be transmitted from a computer storing the program in a storage device or the like to another computer via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer, what is called a difference file (difference program) may be sufficient.

  The present invention can be widely applied to various stream cipher evaluations. Therefore, it can be widely used for system construction in broadband communication using stream cipher and mobile communication including mobile phones.

The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

It is a block diagram of the encryption apparatus which concerns on 1st Embodiment. It is a flow which shows the encryption process in the encryption apparatus which concerns on 1st Embodiment. It is a block diagram of the decoding apparatus which concerns on 1st Embodiment. It is a flow which shows the decoding process in the decoding apparatus which concerns on 1st Embodiment. It is a block diagram of the self-synchronous encryption apparatus which concerns on 1st Embodiment. It is a flow which shows the encryption process in the self-synchronous encryption apparatus which concerns on 1st Embodiment. It is a block diagram of the self-synchronous decoding device according to the first embodiment. It is a flow which shows the decoding process in the self-synchronous decoding apparatus which concerns on 1st Embodiment.

Explanation of symbols

  10, 20 ... key sequence generation function, 11 ... internal state update function, 12 ... internal state storage memory, 17a, 17b, 17c, ..., 17n, 18a, 18b, 18c, ... , 18n, 27a, 27b, 27c,..., 27n, 29a, 29b, 29c,..., 29n exclusive OR calculator, 21 ... key expansion function, 22 ... expanded key storage memory, 28, 30 ... compression function

Claims (12)

A stream cipher encryption device that inputs plaintext and outputs ciphertext,
An internal state update function that generates an initial key and an initial vector and updates the internal state when the key sequence is output;
Internal state storage means for storing the internal state output from the internal state update function;
A key sequence generation function for reading the internal state stored in the internal state storage means and outputting a key sequence;
An exclusive OR calculator that executes an exclusive OR operation between the key sequence output from the key sequence generation function and the input plaintext, and outputs a ciphertext,
The key sequence generation function outputs a first adder that outputs an addition value of a value in the first internal memory and a value output from the internal state storage means, and a value output from the first adder A first nonlinear function that performs nonlinear processing, a third internal memory that stores a value from the first nonlinear function, a value in the second internal memory, and a value output from the internal state storage means A second adder for outputting an added value; a second nonlinear function for nonlinearly processing the value output from the second adder; and a fourth internal for storing a value from the second nonlinear function A first exclusive OR calculator that executes an exclusive OR operation between a value of the first internal memory and a value output from the internal state storage means and outputs a key sequence; Exclusive logic between the value of the second internal memory and the value output from the internal state storage means A second exclusive OR calculator that executes an operation and outputs a key sequence; and performs an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means A third exclusive OR calculator for outputting a key sequence and executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means to obtain the key sequence A stream cipher encryption apparatus comprising a predetermined number of concatenations according to the length of a key sequence for outputting a function unit comprising a fourth exclusive OR calculator for output.   The key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. 2. The stream cipher encryption apparatus according to claim 1, wherein a predetermined number of connections are connected. A stream cipher encryption method using the stream cipher encryption device according to claim 1 or 2,
A first step of reading an initial key and an initial vector into an internal state memory;
A second step of stirring the internal state memory by the initial stirring process;
A third step in which the key sequence generation function reads the value of the internal state memory and outputs the key sequence;
A fourth step of updating the internal state memory;
A fifth step of outputting a ciphertext by exclusive OR operation of the output key sequence and plaintext;
A stream cipher encryption method characterized by comprising: A program for causing a computer to execute a stream cipher encryption method using the stream cipher encryption apparatus according to claim 1,
A first step of reading an initial key and an initial vector into an internal state memory;
A second step of stirring the internal state memory by the initial stirring process;
A third step in which the key sequence generation function reads the value of the internal state memory and outputs the key sequence;
A fourth step of updating the internal state memory;
A fifth step of outputting a ciphertext by exclusive OR operation of the output key sequence and plaintext;
A program that causes a computer to execute. A decryption device for stream cipher that inputs ciphertext and outputs plaintext,
An internal state update function that generates an initial key and an initial vector and updates the internal state when the key sequence is output;
Internal state storage means for storing the internal state output from the internal state update function;
A key sequence generation function for reading the internal state stored in the internal state storage means and outputting a key sequence;
An exclusive OR calculator that executes an exclusive OR operation between the key sequence output from the key sequence generation function and the input ciphertext, and outputs plaintext,
The key sequence generation function outputs a first adder that outputs an addition value of a value in the first internal memory and a value output from the internal state storage means, and a value output from the first adder A first nonlinear function that performs nonlinear processing, a third internal memory that stores a value from the first nonlinear function, a value in the second internal memory, and a value output from the internal state storage means A second adder for outputting an added value; a second nonlinear function for nonlinearly processing the value output from the second adder; and a fourth internal for storing a value from the second nonlinear function A first exclusive OR calculator that executes an exclusive OR operation between a value of the first internal memory and a value output from the internal state storage means and outputs a key sequence; Exclusive logic between the value of the second internal memory and the value output from the internal state storage means A second exclusive OR calculator that executes an operation and outputs a key sequence; and performs an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means A third exclusive OR calculator for outputting a key sequence and executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means to obtain the key sequence A stream cipher decryption device, wherein a predetermined number of key units are connected in accordance with the length of a key sequence for outputting a function unit comprising a fourth exclusive OR calculator for output.   The key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. 6. The apparatus for decrypting a stream cipher according to claim 5, wherein a predetermined number are connected. A self-synchronous stream cipher encryption device that inputs plaintext, outputs ciphertext, and feeds back the ciphertext to the input,
A key expansion function that inputs an initial value and generates an expanded key;
Expanded key storage means for storing the generated expanded key;
A key sequence generation function that reads the expanded key stored in the expanded key storage means and the previously encrypted ciphertext or initial vector, and outputs a key sequence;
An exclusive OR operator that executes an exclusive OR operation between the key sequence output from the key sequence generation function and the input plaintext, and outputs a ciphertext;
A compression function that compresses the output ciphertext and feeds it back to the key sequence generation function;
With
The key sequence generation function outputs a first adder that outputs an addition value of a value in the first internal memory and a value output from the internal state storage means, and a value output from the first adder A first nonlinear function that performs nonlinear processing, a third internal memory that stores a value from the first nonlinear function, a value in the second internal memory, and a value output from the internal state storage means A second adder for outputting an added value; a second nonlinear function for nonlinearly processing the value output from the second adder; and a fourth internal for storing a value from the second nonlinear function A first exclusive OR calculator that executes an exclusive OR operation between a value of the first internal memory and a value output from the internal state storage means and outputs a key sequence; Exclusive logic between the value of the second internal memory and the value output from the internal state storage means A second exclusive OR calculator that executes an operation and outputs a key sequence; and performs an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means A third exclusive OR calculator for outputting a key sequence and executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means to obtain the key sequence An encryption device for self-synchronous stream ciphers, wherein a predetermined number is connected according to the length of a key sequence for outputting a function unit comprising a fourth exclusive OR calculator for output.   The key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. 8. The self-synchronous stream cipher encryption apparatus according to claim 7, wherein a predetermined number of connections are connected. A stream cipher encryption method using the stream cipher self-synchronous encryption apparatus according to claim 7 or 8,
A first step of expanding an initial key with a key expansion function and setting it in memory as an expanded key;
A second step in which the key sequence generation function reads the expanded key and the previously encrypted ciphertext or initial vector and outputs the key sequence;
A third step of outputting a ciphertext by performing an exclusive OR operation between the key sequence and the plaintext;
A fourth step of feeding back the output ciphertext and inputting it to the key generation function;
A stream cipher encryption method characterized by comprising: A program for causing a computer to execute a stream cipher encryption method using the stream cipher self-synchronous encryption apparatus according to claim 7 or 8,
A first step of expanding an initial key with a key expansion function and setting it in memory as an expanded key;
A second step in which the key sequence generation function reads the expanded key and the previously encrypted ciphertext or initial vector and outputs the key sequence;
A third step of outputting a ciphertext by performing an exclusive OR operation between the key sequence and the plaintext;
A fourth step of feeding back the output ciphertext and inputting it to the key generation function;
A program that causes a computer to execute. A decryption device for a self-synchronous stream cipher that inputs ciphertext and outputs plaintext,
A key expansion function that inputs an initial value and generates an expanded key;
Expanded key storage means for storing the generated expanded key;
A key sequence generation function that reads the expanded key stored in the expanded key storage means and the plaintext or initial vector decrypted last time, and outputs a key sequence;
An exclusive OR calculator that performs an exclusive OR operation between the key sequence output from the key sequence generation function and the input ciphertext, and outputs a plaintext;
A compression function for compressing the output plaintext and feeding back to the key sequence generation function;
With
The key sequence generation function outputs a first adder that outputs an addition value of a value in the first internal memory and a value output from the internal state storage means, and a value output from the first adder A first nonlinear function that performs nonlinear processing, a third internal memory that stores a value from the first nonlinear function, a value in the second internal memory, and a value output from the internal state storage means A second adder for outputting an added value; a second nonlinear function for nonlinearly processing the value output from the second adder; and a fourth internal for storing a value from the second nonlinear function A first exclusive OR calculator that executes an exclusive OR operation between a value of the first internal memory and a value output from the internal state storage means and outputs a key sequence; Exclusive logic between the value of the second internal memory and the value output from the internal state storage means A second exclusive OR calculator that executes an operation and outputs a key sequence; and performs an exclusive OR operation between the value of the third internal memory and the value output from the internal state storage means A third exclusive OR calculator for outputting a key sequence and executing an exclusive OR operation between the value of the fourth internal memory and the value output from the internal state storage means to obtain the key sequence A decoding device for self-synchronous stream ciphers, wherein a predetermined number of units are connected in accordance with the length of a key sequence for outputting a function unit comprising a fourth exclusive OR calculator for output.   The key sequence generation function further includes a preprocessing unit comprising an adder, a nonlinear function for nonlinearly processing the output of the adder, and an internal memory for storing a value from the nonlinear function. 12. The self-synchronous stream cipher decryption apparatus according to claim 11, wherein a predetermined number of the cipher streams are connected.

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