JP2009288339A - Ciphering device and deciphering device for stream cipher, mac generating device, ciphering method and deciphering method for stream cipher, mac generating method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the security of existing streaming cipher without adding different logic. <P>SOLUTION: A ciphering device for stream cipher includes: a first initialization processing means receiving the input of an initial key and an initial vector to perform initialization processing; a first key sequence generation processing means performing key sequence generation processing to generate a key sequence having the data length equivalent to the initial key and the initial vector; a second initialization processing means performing the initialization processing by regarding the generated key sequence as a new initial key; a second key sequence generation processing means performing the key sequence generation processing to generate a key sequence having the data length equivalent to a plaintext; and an exclusive OR operation means performing the exclusive OR operation of bit data of the generated key sequence and the plaintext to output a ciphertext. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a stream cipher encryption apparatus, a decryption apparatus, a MAC generation apparatus, a stream cipher encryption method, a decryption method, a MAC generation method, and a program for improving the safety of an existing stream cipher.

  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.

Since the stream encryption method can be expected to process faster than the block encryption method, for example, as a method for transmitting large-capacity data such as a movie in recent years, attention has been paid to the stream encryption method. There is a problem that the encryption process and the decryption process must be synchronized. For this reason, a self-synchronous stream cipher apparatus that automatically recovers synchronization using a ciphertext received without error of a certain size or more has been proposed (for example, see Patent Document 1).
JP 2001-16197 A

  By the way, in the stream cipher, the initial key is stirred by the initialization process, the initial internal state is generated, and each sequence of encryption is generated while sequentially updating the generated state. However, the conventional stream cipher has a problem that when an internal state is leaked by some means (memory dump or the like), an initial key is derived therefrom. In addition, there is a method to make it impossible to derive the initial key by using a special function (for example, hash function) for initialization processing, but there is a problem that the implementation size increases because different logic is added. .

  Therefore, the present invention has been made in view of the above-described problems, and an encryption apparatus, a decryption apparatus, and a MAC generation apparatus for stream ciphers that improve the safety of existing stream ciphers without adding different logic. An object of the present invention is to provide an encryption method, a decryption method, a MAC generation method, and a program for stream encryption.

  The present invention proposes the following matters in order to solve the above problems.

  (1) According to the present invention, first initialization processing means for executing an initialization process by inputting an initial key and an initial vector, a key sequence generation process, and data equivalent to the initial key and the initial vector A first key sequence generation processing unit that generates a long key sequence, a second initialization processing unit that executes the initialization process by regarding the generated key sequence as a new initial key, and a key sequence generation process A second key sequence generation processing means for generating a key sequence having a data length equivalent to the plaintext, and performing an exclusive OR operation between the generated bit data of the key sequence and the plaintext, And a stream cipher encrypting device characterized by comprising an exclusive OR operation means for outputting.

  According to this invention, the first initialization processing means inputs the initial key and the initial vector and executes the initialization process. The first key sequence generation processing means executes a key sequence generation process to generate a key sequence having a data length equivalent to the initial key and the initial vector. The second initialization processing means regards the generated key sequence as a new initial key and executes initialization processing. The second key sequence generation processing means executes a key sequence generation process to generate a key sequence having a data length equivalent to that of plain text. Then, the exclusive OR operation means performs an exclusive OR operation between the generated bit data of the key sequence and the plaintext, and outputs a ciphertext. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (2) The present invention executes the processing of the first initialization processing means and the processing of the first key sequence generation processing means in the tamper resistant device in the stream cipher encryption device of (1). A stream cipher encryption device characterized by this is proposed.

  According to this invention, the process of the first initialization processing unit and the process of the first key sequence generation processing unit are executed in the tamper resistant device. Therefore, this can further improve safety.

  (3) According to the present invention, in the stream cipher encryption apparatus of (1) or (2), an initial value different from an initial key and an initial vector used in the past for the initialization processing of the first initialization processing means A stream cipher encryption apparatus using a key and an initial vector has been proposed.

  According to the present invention, the initial key and the initial vector used in the past are not used for the initialization processing of the first initialization processing means. Therefore, this can further improve safety.

  (4) According to the present invention, first initialization processing means for executing an initialization process by inputting an initial key and an initial vector, a key sequence generation process, and data equivalent to the initial key and the initial vector A first key sequence generation processing unit that generates a long key sequence, a second initialization processing unit that executes the initialization process by regarding the generated key sequence as a new initial key, and a key sequence generation process A second key sequence generation processing means for generating a key sequence having a data length equivalent to the ciphertext, and performing an exclusive OR operation between the bit data of the generated key sequence and the ciphertext, A stream cipher decryption device characterized by comprising an exclusive OR operation means for outputting plaintext is proposed.

  According to this invention, the first initialization processing means inputs the initial key and the initial vector and executes the initialization process. The first key sequence generation processing means executes a key sequence generation process to generate a key sequence having a data length equivalent to the initial key and the initial vector. The second initialization processing means regards the generated key sequence as a new initial key and executes initialization processing. The second key sequence generation processing means executes a key sequence generation process and generates a key sequence having a data length equivalent to that of the ciphertext. Then, the exclusive OR operation means performs an exclusive OR operation between the generated bit sequence bit data and the ciphertext, and outputs a plaintext. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (5) According to the present invention, first initialization processing means for executing an initialization process by inputting an initial key and an initial vector, a key sequence generation process, and data equivalent to the initial key and the initial vector A first key sequence generation processing unit that generates a long key sequence, a second initialization processing unit that executes the initialization process by regarding the generated key sequence as a new initial key, and a key sequence generation process A second key sequence generation processing unit that generates a key sequence having a data length equivalent to that of plaintext, and an exclusive OR operation between the key sequence generated by the second key sequence generation unit and the plaintext. And an exclusive OR operation means for outputting the final ciphertext as a message authenticator and feeding back the operation result to the first initialization processing means. Has proposed.

  According to this invention, the first initialization processing means inputs the initial key and the initial vector and executes the initialization process. The first key sequence generation processing means executes a key sequence generation process to generate a key sequence having a data length equivalent to the initial key and the initial vector. The second initialization processing means regards the generated key sequence as a new initial key and executes initialization processing. The second key sequence generation processing means executes a key sequence generation process to generate a key sequence having a data length equivalent to that of plain text. The exclusive OR operation means performs an exclusive OR operation between the generated key sequence and the plaintext, feeds back the operation result to the first initialization processing means, and sends the final ciphertext as a message. Output as an authenticator. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (6) In the present invention, a first step of inputting an initial key and an initial vector and executing an initialization process, a key sequence generation process, and a key having a data length equivalent to the initial key and the initial vector A second step for generating a sequence, a third step for executing the initialization process by regarding the generated key sequence as a new initial key, a key sequence generation process, and a data length equivalent to plaintext And a fifth step of performing an exclusive OR operation between the bit data of the generated key sequence and the plaintext, and outputting a ciphertext. A stream cipher encryption method has been proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, initialization processing is executed, and key sequence generation processing is executed to generate a key sequence having a data length equivalent to that of plain text. Then, an exclusive OR operation between the generated bit data of the key sequence and the plaintext is performed, and a ciphertext is output. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (7) In the present invention, a first step of inputting an initial key and an initial vector and executing an initialization process, a key sequence generation process, and a key having a data length equivalent to the initial key and the initial vector A second step of generating a sequence, a third step of executing the initialization process by regarding the generated key sequence as a new initial key, and executing the key sequence generation process to obtain data equivalent to the ciphertext A fourth step of generating a long key sequence, and a fifth step of performing an exclusive OR operation between the bit data of the generated key sequence and the ciphertext, and outputting a plaintext. Has been proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, an initialization process is executed, and a key sequence generation process is executed to generate a key sequence having a data length equivalent to the ciphertext. Then, an exclusive OR operation is performed on the generated bit data of the key sequence and the ciphertext, and a plaintext is output. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (8) According to the present invention, a first step of inputting an initial key and an initial vector and executing an initialization process, a key sequence generation process, and a key having a data length equivalent to the initial key and the initial vector A second step for generating a sequence, a third step for executing the initialization process by regarding the generated key sequence as a new initial key, a key sequence generation process, and a data length equivalent to plaintext A fourth step of generating the key sequence of X, and performing an exclusive OR operation between the generated key sequence and the plaintext, feeding back the operation result to the first step, and obtaining a final ciphertext A MAC generation method characterized by comprising a fifth step of outputting as a message authenticator is proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, initialization processing is executed, and key sequence generation processing is executed to generate a key sequence having a data length equivalent to that of plain text. Then, an exclusive OR operation between the generated key sequence and the plaintext is performed, and the operation result is fed back to the first step, and the final ciphertext is output as a message authenticator. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (9) According to the present invention, a first step of executing an initialization process by inputting an initial key and an initial vector to a computer, executing a key sequence generation process, and data equivalent to the initial key and the initial vector A second step of generating a long key sequence, a third step of executing the initialization process by regarding the generated key sequence as a new initial key, executing the key sequence generation process, and equivalent to plain text And a fourth step of generating a ciphertext by performing an exclusive OR operation on the bit data of the generated key sequence and the plaintext. A stream cipher encryption program has been proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, initialization processing is executed, and key sequence generation processing is executed to generate a key sequence having a data length equivalent to that of plain text. Then, an exclusive OR operation between the generated bit data of the key sequence and the plaintext is performed, and a ciphertext is output. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (10) According to the present invention, a first step of executing an initialization process by inputting an initial key and an initial vector to a computer and executing a key sequence generation process and data equivalent to the initial key and the initial vector A second step of generating a long key sequence; a third step of executing the initialization process by regarding the generated key sequence as a new initial key; executing the key sequence generation process; A fourth step of generating a key sequence having an equivalent data length, and a fifth step of performing an exclusive OR operation between the bit data of the generated key sequence and the ciphertext, and outputting a plaintext. A stream cipher decryption program for execution is proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, an initialization process is executed, and a key sequence generation process is executed to generate a key sequence having a data length equivalent to the ciphertext. Then, an exclusive OR operation is performed on the generated bit data of the key sequence and the ciphertext, and a plaintext is output. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  (11) In the present invention, a first step of executing an initialization process by inputting an initial key and an initial vector to a computer, executing a key sequence generation process, and data equivalent to the initial key and the initial vector A second step of generating a long key sequence, a third step of executing the initialization process by regarding the generated key sequence as a new initial key, executing the key sequence generation process, and equivalent to plain text A fourth step of generating a key sequence having a data length of X, and performing an exclusive OR operation of the generated key sequence and plaintext, feeding back the operation result to the first step, and finally A MAC generation program for executing the fifth step of outputting a ciphertext as a message authenticator is proposed.

  According to the present invention, an initial key and an initial vector are input, initialization processing is executed, and then key sequence generation processing is executed to generate a key sequence having a data length equivalent to the initial key and the initial vector. . Further, the generated key sequence is regarded as a new initial key, initialization processing is executed, and key sequence generation processing is executed to generate a key sequence having a data length equivalent to that of plain text. Then, an exclusive OR operation between the generated key sequence and the plaintext is performed, and the operation result is fed back to the first step, and the final ciphertext is output as a message authenticator. Therefore, the security of the existing stream cipher can be improved without adding different logic.

  According to the present invention, there is an effect that it is possible to construct a mechanism in which an initial key cannot be derived even if the internal state is leaked. There is an effect that the security of the existing stream cipher can be improved without adding different logic.

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]
<Configuration of Stream Cipher Encryption Device>
As shown in FIG. 1, the stream cipher encryption apparatus according to the present embodiment includes an initialization processing unit 1a, a key sequence generation processing unit 2a, an initialization processing unit 1b, a key sequence generation processing unit 2b, And an exclusive OR calculator (XOR) 3.

  The initialization processing unit 1a inputs an initial key and an initial vector and executes initialization processing. The key sequence generation processing unit 2a executes a key sequence generation process to generate a key sequence having a data length equivalent to that of the initial key and the initial vector. It is more preferable that the processing of the initialization processing unit 1a and the key sequence generation processing unit 2a are executed in the tamper resistant device. That is, by executing the processing of the initialization processing unit 1a and the key sequence generation processing unit 2a within the tamper resistant device, the safety can be further improved. Also, the initial key and initial vector used in the past are not used for the initialization processing of the initialization processing unit 1a. Thereby, safety can be further improved.

  The initialization processing unit 1b performs initialization processing by regarding the key sequence generated by the key sequence generation processing unit 2a as a new initial key. The key sequence generation processing unit 2b executes a key sequence generation process, and generates a key sequence having a data length equivalent to that of plain text.

  The exclusive OR operator (XOR) 3 inputs the bit string of the key sequence generated by the key sequence generation processing unit 2b and the plaintext, and outputs the ciphertext by executing these exclusive OR operations.

<Processing of encryption device for stream cipher>
Next, the processing of the stream cipher encryption apparatus will be described with reference to FIG.

  First, the initialization processing unit 1a inputs an initial key and an initial vector (IV) and performs a normal initialization process (step S101). Next, the key sequence generation processing unit 2a executes key sequence generation processing, and generates a key sequence until the length is equal to the initial key and the initial vector (IV) (step S102).

  Further, the initialization processing unit 1b regards the key sequence generated by the key sequence generation processing unit 2a as a new initial key and initial vector (IV), and executes an initialization process (step S103). The key sequence generation processing unit 2b executes a key sequence generation process, and generates a key sequence until the length is equal to that of plain text (step S104).

  Then, the key sequence bit string generated by the key sequence generation processing unit 2b and the plaintext are input to the exclusive OR calculator (XOR) 3 to perform an exclusive OR operation and output as a ciphertext (step S105). .

  Accordingly, the stream cipher encryption apparatus of the present embodiment is configured to execute the initialization process and the key sequence generation process in two stages, so that the security of the existing stream cipher can be added without adding different logic. Can be improved.

[Second Embodiment]
<Configuration of Decryption Device for Stream Cipher>
As shown in FIG. 3, the stream cipher decryption device according to the present embodiment includes an initialization processing unit 1a, a key sequence generation processing unit 2a, an initialization processing unit 1b, and a key sequence generation processing unit 2b. And an exclusive OR calculator (XOR) 4. In addition, about the element which attaches | subjects the code | symbol similar to 1st Embodiment, since it has the same function, detailed description is abbreviate | omitted. In the stream cipher decryption apparatus according to the present embodiment, an exclusive OR calculator (XOR) 4 is generated by the key sequence generation processing unit 2b as compared with the stream cipher encryption apparatus according to the first embodiment. The key sequence and the ciphertext are inputted, and a plaintext is outputted by executing these exclusive OR operations.

<Processing of Decryption Device for Stream Cipher>
Next, the processing of the stream cipher decryption apparatus will be described with reference to FIG.
First, the initialization processing unit 1a inputs an initial key and an initial vector (IV) and performs a normal initialization process (step S201). Next, the key sequence generation processing unit 2a executes key sequence generation processing, and generates a key sequence until the length is equal to the initial key and the initial vector (IV) (step S202).

  Further, the initialization processing unit 1b regards the key sequence generated by the key sequence generation processing unit 2a as a new initial key and an initial vector (IV), and executes an initialization process (step S203). The key sequence generation processing unit 2b executes a key sequence generation process, and generates a key sequence until the length is equal to that of plain text (step S204).

  Then, the key sequence bit string generated by the key sequence generation processing unit 2b and the ciphertext are input to the exclusive OR calculator (XOR) 4 to perform an exclusive OR operation and output as a ciphertext (step S205). ).

  Therefore, in the stream cipher decryption apparatus according to the present embodiment, the initialization process and the key sequence generation process are executed in two stages, so that the security of the existing stream cipher can be added without adding different logic. Can be improved.

[Third Embodiment]
<Configuration of MAC generator>
As shown in FIG. 5, the MAC generating apparatus according to the present embodiment includes an initialization processing unit 1a, a key sequence generation processing unit 2a, an initialization processing unit 1b, a key sequence generation processing unit 2b, an exclusive logic And a sum calculator (XOR) 3. In addition, about the element which attaches | subjects the code | symbol similar to 1st Embodiment, since it has the same function, detailed description is abbreviate | omitted. The basic configuration of the MAC generation apparatus according to the present embodiment is the same as that of the stream cipher encryption apparatus according to the first embodiment, except that the ciphertext output from the exclusive OR calculator (XOR) 3 is initialized. The difference is that it is fed back to the processing unit 1a.

<Process of MAC generator>
Next, processing of the MAC generation device will be described with reference to FIG.
First, the initialization processing unit 1a inputs an initial key and an initial vector (IV) and performs a normal initialization process (step S301). Next, the key sequence generation processing unit 2a executes key sequence generation processing, and generates a key sequence until the length is equal to the initial key and the initial vector (IV) (step S302).

  Further, the initialization processing unit 1b regards the key sequence generated by the key sequence generation processing unit 2a as a new initial key and an initial vector (IV), and executes an initialization process (step S303). The key sequence generation processing unit 2b executes a key sequence generation process and generates a key sequence until the length is equal to that of plain text (step S304).

  Then, the key sequence bit string generated by the key sequence generation processing unit 2b and the plaintext are input to an exclusive OR operator (XOR) 3, and an exclusive OR operation is performed and output as a ciphertext. Is fed back to the conversion processing unit 1a (step S305).

  Then, it is determined whether or not all plaintexts have been input (step S306). When it is determined that all plaintexts have been input (“Yes” in step S306), a message authenticator is output (step S307). When it is determined that no plaintext is input (“No” in step S306), the process returns to step S301 to continue the process.

  Therefore, since the MAC generation apparatus of the present embodiment is configured to execute the initialization process and the key sequence generation process in two stages, the safety of the existing stream cipher is improved without adding different logic. be able to.

  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 read by a stream cipher encryption device, a stream cipher decryption device, and a MAC generation device, By executing this, the stream cipher encryption apparatus, stream cipher decryption apparatus, and MAC generation apparatus of the present invention can be realized.

  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.

  Note that 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 figure which shows the structure of the encryption apparatus of the stream encryption which concerns on 1st Embodiment. It is a processing flow of the encryption apparatus of the stream encryption which concerns on 1st Embodiment. It is a figure which shows the structure of the decoding apparatus of the stream encryption which concerns on 2nd Embodiment. It is a processing flow of the decryption apparatus of the stream encryption which concerns on 2nd Embodiment. It is a figure which shows the structure of the MAC production | generation apparatus which concerns on 3rd Embodiment. It is a processing flow of the MAC production | generation apparatus which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Initialization process part 1b ... Initialization process part 2a ... Key sequence production | generation process part 2b ... Key series production | generation process part 3, 4 ... Exclusive OR operator (XOR)

Claims (11)

First initialization processing means for inputting an initial key and an initial vector and executing initialization processing;
First key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A second initialization processing means for performing the initialization processing by regarding the generated key sequence as a new initial key;
Second key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to plaintext;
An exclusive OR operation means for performing an exclusive OR operation between the generated bit data of the key sequence and the plaintext, and outputting a ciphertext;
A stream cipher encryption apparatus comprising:   2. The stream cipher encryption apparatus according to claim 1, wherein the processing of the first initialization processing unit and the processing of the first key sequence generation processing unit are executed in a tamper resistant device.   3. The stream cipher according to claim 1, wherein an initial key and an initial vector different from an initial key and an initial vector used in the past are used for an initialization process of the first initialization processing unit. Encryption device. First initialization processing means for inputting an initial key and an initial vector and executing initialization processing;
First key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A second initialization processing means for performing the initialization processing by regarding the generated key sequence as a new initial key;
Second key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to the ciphertext;
An exclusive OR operation means for performing an exclusive OR operation between the generated bit data of the key sequence and the ciphertext, and outputting a plaintext;
An apparatus for decrypting a stream cipher, comprising: First initialization processing means for inputting an initial key and an initial vector and executing initialization processing;
First key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A second initialization processing means for performing the initialization processing by regarding the generated key sequence as a new initial key;
Second key sequence generation processing means for executing a key sequence generation process and generating a key sequence having a data length equivalent to plaintext;
The exclusive OR operation of the key sequence generated by the second key sequence generation means and the plaintext is performed, the result of the operation is fed back to the first initialization processing means, and the final ciphertext is sent to the message An exclusive OR operation means for outputting as an authenticator;
A MAC generation device comprising: A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to plaintext;
A fifth step of performing an exclusive OR operation between the generated bit data of the key sequence and the plaintext, and outputting a ciphertext;
A stream cipher encryption method characterized by comprising: A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to the ciphertext;
A fifth step of performing an exclusive OR operation between the generated bit data of the key sequence and the ciphertext, and outputting a plaintext;
A method of decrypting a stream cipher, comprising: A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to plaintext;
A fifth step of performing an exclusive OR operation between the generated key sequence and plaintext, feeding back the operation result to the first step, and outputting a final ciphertext as a message authenticator;
A MAC generation method comprising: On the computer,
A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to plaintext;
A fifth step of performing an exclusive OR operation between the generated bit data of the key sequence and the plaintext, and outputting a ciphertext;
Stream cipher encryption program to execute. On the computer,
A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to the ciphertext;
A fifth step of performing an exclusive OR operation between the generated bit data of the key sequence and the ciphertext, and outputting a plaintext;
Stream cipher decryption program for executing On the computer,
A first step of inputting an initial key and an initial vector and executing an initialization process;
Executing a key sequence generation process, and generating a key sequence having a data length equivalent to the initial key and the initial vector;
A third step of performing the initialization process by regarding the generated key sequence as a new initial key;
A fourth step of executing a key sequence generation process to generate a key sequence having a data length equivalent to plaintext;
A fifth step of performing an exclusive OR operation between the generated key sequence and plaintext, feeding back the operation result to the first step, and outputting a final ciphertext as a message authenticator;
MAC generation program for executing

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