Encryption method, decryption method, cryptographic communication system and encryption device
AssigneeMurata Kikai Kabushiki Kaisha
InventorsDaisuke Suzuki, Yasuyuki Murakami, Ryuichi Sakai, Masao Kasahara
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Abstract
After an extended transformation of a plaintext, a reduced product-sum type encryption is carried out. The plaintext to be encrypted is divided thereby to obtain a plaintext vector. The plaintext vector is transformed by a predetermined function thereby to generate a transformation vector. Then, a ciphertext is generated by a product-sum operation between the components of a public key vector and the components of the plaintext vector and the transformation vector.
Claims19
An encryption method, comprising the steps of:
- dividing a plaintext to be encrypted thereby to obtain a plaintext vector;
- applying a predetermined transformation on the plaintext vector thereby to generate a transformation vector;
- and
- generating a ciphertext by a product-sum operation between the components of a public key vector and the components of the plaintext vector and the transformation vector.
An encryption method, comprising the step of:
- generating a product-sum type ciphertext using a first vector depending on a plaintext and a second vector having components obtained by a modulo transformation of base products;
- wherein
- the first vector is composed of:
- a plaintext vector obtained by dividing a plaintext to be encrypted;
- and a transformation vector obtained by a transformation of the plaintext vector using a predetermined function;
- and wherein the base product is obtained by both normal bases satisfying bi>mi-1 (bi is a base in the base product, mi-1 is a component of the first vector, i is an element of a subset S of a universal set U={2,3, . . . , K}, and K is the number of components of the first and second vector) and reduced bases satisfying bj≦mj-1 (bj is a base in the base product, mj-1 is a component of the first vector, and j is an element of a complementary set of the subset S).
An encryption device for generating a product-sum type ciphertext from a plaintext, comprising a controller capable of performing the operations of:
- (i) dividing a plaintext to be encrypted thereby to obtain a plaintext vector;
- (ii) applying a predetermined transformation on the plaintext vector thereby to generate a transformation vector;
- and
- (iii) generating a ciphertext by a product-sum operation between the components of a public key vector and the components of the plaintext vector and the transformation vector.
A computer memory product having computer readable program code means for causing a computer to generate a product-sum type ciphertext from a plaintext, said computer readable program code means comprising:
- program code means for causing the computer to divide a plaintext to be encrypted thereby to obtain a plaintext vector;
- program code means for causing the computer to apply a predetermined transformation on the plaintext vector thereby to generate a transformation vector;
- and
- program code means for causing the computer to generate a ciphertext by a product-sum operation between the components of a public key vector and the components of the plaintext vector and the transformation vector.
A computer data signal embodied in a carrier wave for transmitting a program, the program being configured to cause a computer to generate a product-sum type ciphertext from a plaintext, comprising:
- a code segment for causing the computer to divide a plaintext to be encrypted thereby to obtain a plaintext vector;
- a code segment for causing the computer to apply a predetermined transformation on the plaintext vector thereby to generate a transformation vector;
- and
- a code segment for causing the computer to generate a ciphertext by a product-sum operation between the components of a public key vector and the components of the plaintext vector and the transformation vector.
Dependencies are inferred from the claim text.