Cryptography – Communication system using cryptography – Time segment interchange
Reexamination Certificate
1999-02-05
2002-12-31
Barrón, Gilberto (Department: 2132)
Cryptography
Communication system using cryptography
Time segment interchange
C713S189000, C712S034000, C709S241000
Reexamination Certificate
active
06501840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cryptographic processing apparatus and a user apparatus for the cryptographic processing apparatus, a cryptographic processing method and a user method for the cryptographic processing method, and a recording medium for recording a program, used as a means for secure communications.
2. Description of the Prior Art
Cryptographic methods are used for protecting important information from being intercepted by third parties. various privacy communication apparatuses that use cryptographic methods have been developed.
PKCS#11 (Cryptographic Token Interface Standard) proposed by RSA Data Security, Inc. defines an interface linking a cryptographic processing apparatus and a user apparatus for the cryptographic processing apparatus, where a system that uses cryptographic methods is divided into a cryptographic processing apparatus and a user apparatus.
According to this standard, the cryptographic processing apparatus first receives (1) text data, such as plain text and cipher text, (2) a specification of a cryptographic processing type, such as encryption, decryption, digital signature generation, digital signature verification, and message digesting, and (3) a specification of an algorithm type that includes information relating to the computation/calculation method and a key size. The cryptographic processing apparatus then generates cryptographically processed data, such as cipher text (encrypted plain text) and plain text (decrypted cipher text), by processing the received text data according to the cryptographic method that corresponds to the received cryptographic processing type specification and algorithm type specification. Finally, the cryptographic processing apparatus outputs the generated cryptographically processed data to the user apparatus. The user apparatus (1) outputs the plain text, the cipher text, the cryptographic processing type specification, and the algorithm type specification to the cryptographic processing apparatus, (2) receives the cryptographically processed data from the cryptographic processing apparatus, and (3) may send the received cryptographically processed data to other user apparatuses.
It should be noted here that the cryptographic processing type and the algorithm type are together hereinafter referred to as the cryptographic algorithm.
The interface defined by PKCS#11 offers a number of advantages. For instance, when the cryptographic processing apparatus supports a plurality of cryptographic algorithms, the user apparatus can use any of these cryptographic algorithms by merely specifying the desired cryptographic algorithm. Also, when a new cryptographic method is devised, only the design of the cryptographic processing apparatus needs to be changed. Therefore, the design of the user apparatus does not need to be changed. Furthermore, when a new application of a existing cryptographic method is devised, only the design of the user apparatus needs to be changed. Therefore, the design of the cryptographic processing apparatus does not need to be changed.
In general, every cryptographic method corresponding to a cryptographic processing type and an algorithm type processes data in the same way. That is, plain text or cipher text is processed according to the cryptographic method and encrypted plain text or decrypted cipher text is output. The relation between the sizes of the input data and the output data differs depending on the cryptographic algorithm used. Consequently, the memory area for storing the output data is allocated in advance according to prestored information as to the output data sizes which correspond to respective cryptographic processing types and algorithm types.
Cryptographic processing methods can be classified into stream cipher and block cipher. With the stream cipher, the cryptographic processing is performed on each character in character strings to be processed. With the block cipher, character strings to be processed are divided into blocks of a certain size and each of the blocks is processed according to the block cipher. For instance, when input data, such as plain text, is processed according to the block cipher, the user apparatus divides the input data into blocks according to a block size and outputs the blocks to the cryptographic processing apparatus. The cryptographic processing apparatus processes each block output from the user apparatus according to the block cipher. Therefore, the cryptographic processing apparatus does not need to perform a buffering process or a padding process to make the input data a multiple of the block size. As a result, the cryptographic processing apparatus can perform the cryptographic processing efficiently when a block cipher is used. Because the suitable block size differs depending on the cryptographic algorithm and key size used, the user apparatus determines the size of each input data block for the cryptographic processing apparatus according to a pre-registered list of input data block sizes for respective cryptographic processing types and algorithm types.
As described above, when a cryptographic system where the user apparatus and the cryptographic processing apparatus are linked by an interface is developed, the cryptographic processing apparatus stores algorithms for a plurality of cryptographic methods. Therefore, the user apparatus only needs to specify a cryptographic algorithm to the cryptographic processing apparatus to use the cryptographic algorithm. However, because the user apparatus stores output data sizes and input data block sizes for respective cryptographic processing types and algorithm types, the design of the user apparatus needs to be changed when a new cryptographic processing type or a new algorithm type is devised.
SUMMARY OF THE INVENTION
In view of the stated problems, it is the object of the present invention to provide a cryptographic processing apparatus and a user apparatus, a cryptographic processing system including the cryptographic processing apparatus and the user apparatus, a cryptographic processing method and a user method, and a recording medium for recording a program of these methods, where the design of the user apparatus does not need to be changed, even when a new cryptographic processing type or a new algorithm type is devised.
To achieve the stated object, the cryptographic system of the present invention includes a user apparatus and a cryptographic processing apparatus, the user apparatus sending a size of first data to the cryptographic processing apparatus and receiving a size of second data from the cryptographic processing apparatus, the cryptographic processing apparatus calculating the size of the second data according to the sent size of the first data and sending the calculated size of the second data to the user apparatus, the second data being generated by processing the first data according to a cryptographic algorithm, where the user apparatus includes a data storage unit, an input size calculation unit, an algorithm specifying unit, and a size receiving unit, and the cryptographic processing apparatus includes an arithmetic expression storage unit, an information receiving unit, an arithmetic expression fetching unit, and an output size calculation unit, where the data storage unit stores the first data, the input size calculation unit reads the first data from the data storage unit, calculates a size of the read first data as a first size, and outputs first size information showing the first size to the information receiving unit, the algorithm specifying unit outputs type information showing an algorithm type that corresponds to a cryptographic algorithm to the information receiving unit, the arithmetic expression storage unit stores at least one pair of an algorithm type and an arithmetic expression, the arithmetic expression being used to calculate an output size from an input size, the output size showing a size of data that would be generated if data of the input size were processed according to a cryp
Barrón Gilberto
Matsushita Electric - Industrial Co., Ltd.
Meislahn Douglas J.
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