Cryptographic system and computer readable medium

Patent metadata

Field	Value
Publication number	US-9640090-B2
Application number	US-201415118797-A
Country	US
Kind code	B2
Filing date	Feb 24, 2014
Priority date	Feb 24, 2014
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A cryptographic system ( 10 ) performs a cryptographic process using a basis. B and a basis B*. An encryption device ( 200 ) generates a ciphertext including a transmission-side vector being a vector in the basis B and being generated using one vector of a first vector consisting of coefficients y j of a polynomial having x i as roots and a second vector consisting of v 1 i being a power of v 1 . A decryption device ( 300 ) decrypts the ciphertext generated by the encryption device ( 200 ) with a decryption key including a reception-side vector being a vector in the basis B* and being generated using the other vector of the first vector and the second vector.

First claim

The invention claimed is:

1. A cryptographic system to perform a cryptographic process using a basis B and a basis B*, the cryptographic system comprising:
processing circuitry to:
generate a transmission-side vector being a vector in the basis B and being generated using one vector of a first vector consisting of coefficients y j (j=1, . . . , n) of a polynomial having attribute information x i (i=1, . . . , n′, n′ being an integer from 1 to n−1, n being an integer of 2 or greater) as roots and a second vector consisting of v 1 i (i=0, . . . , n−1) being a power of predicate information v 1 ;
perform a pairing operation on the transmission-side vector and a reception-side vector being a vector in the basis B* and being generated using another vector of the first vector and the second vector; and
generate at least one of a ciphertext, decryption key and signature output of reduced size containing the transmission-side vector or reception-side vector to reduce processing time of an encryption or decryption process.

2. The cryptographic system according to claim 1 , wherein
the basis B and the basis B* are bases which are generated by transforming a basis A by using a sparse matrix having at least one value other than a constant value 0 in each row and each column.

3. A cryptographic system to perform a cryptographic process using a basis B and a basis B*, the cryptographic system comprising:
processing circuitry to:
generate a transmission-side vector being a vector in the basis B and being generated using one vector of a first vector consisting of coefficients y j (j=1, . . . , n) of a polynomial having attribute information x i (i=1, . . . , n′, n′ being an integer from 1 to n−1, n being an integer of 2 or greater) as roots and a second vector consisting of v 1 i (i=0, . . . , n−1) being a power of predicate information v 1 ;
perform a pairing operation on the transmission-side vector and a reception-side vector being a vector in the basis B* and being generated using another vector of the first vector and the second vector; and
generate at least one of a ciphertext, decryption key, and signature output of reduced size containing the transmission-side vector or reception-side vector to reduce processing time of an encryption or decryption process, wherein
the first vector is a vector indicated in Formula 1, and
the second vector is a vector indicated in Formula 2
{right arrow over ( y )}:=( y 1 , . . . ,y n ) such that Σ j=0 n-1 y n-j z j =z n-1-n′ ·( z−x j )  [Formula 1]

{right arrow over (v)} 1 :=( v 1 n-1n , . . . ,v 1 ,1)  [Formula 2]

4. The cryptographic system according to claim 3 , wherein
the processing circuitry generates at least one of a ciphertext ct Γ including a transmission-side vector c 1 indicated in Formula 3, and
decrypts the ciphertext ct Γ by using a decryption key sk S including a reception-side vector k* i indicated in Formula 4

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Assignees

• Mitsubishi Electric Corp

Inventors

• Takashima Katsuyuki

Classifications

• H04L9/0861

  Generation of secret information including derivation or calculation of cryptographic keys or passwords · CPC title

• H04L2209/24

  Key scheduling, i.e. generating round keys or sub-keys for block encryption · CPC title

• G09C1/00 Primary

  Apparatus or methods whereby a given sequence of signs, e.g. an intelligible text, is transformed into an unintelligible sequence of signs by transposing the signs or groups of signs or by replacing them by others according to a predetermined system (cryptographic typewriters G09C3/00) · CPC title

• H04L9/08

  Key distribution {or management, e.g. generation, sharing or updating, of cryptographic keys or passwords (network architectures or network communication protocols for supporting key management in a packet data network H04L63/06)} · CPC title

• H04L9/3073

  involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing · CPC title