Decoding apparatus, decoding capability providing apparatus, method thereof and program

Patent metadata

Field	Value
Publication number	US-2016133164-A1
Application number	US-201414900517-A
Country	US
Kind code	A1
Filing date	Jun 30, 2014
Priority date	Jul 18, 2013
Publication date	May 12, 2016
Grant date	—

Abstract

A decoding apparatus performs self-correcting processing with a decoding capability providing apparatus holding a decoding key for decoding first ciphertext which can be decoded by homomorphic operation to obtain a decoding value of the first ciphertext, and performs non-homomorphic operation using a value corresponding to or deriving from the decoding value of the first ciphertext and an addition value to output plaintext.

First claim

1 : A decoding apparatus comprising:
a self-correcting processor configured to perform self-correcting processing with a decoding capability providing apparatus holding a decoding key for decoding first ciphertext which can be decoded by homomorphic operation to obtain a decoding value of the first ciphertext; and a non-homomorphic processor configured to perform non-homomorphic operation using a value corresponding to or deriving from the decoding value of the first ciphertext and an addition value to output plaintext.

2 : The decoding apparatus according to claim 1 , wherein
the plaintext is a decoding value of second ciphertext corresponding to or deriving from information comprising the first ciphertext, the first ciphertext is OW-CPA secure for the decoding value of the first ciphertext, and the second ciphertext is IND-CCA secure for the plaintext.

3 : The decoding apparatus according to claim 1 or 2 , wherein
the first ciphertext comprises a value obtained by encrypting a value corresponding to or deriving from a random value, and
the addition value comprises a value corresponding to or deriving from information comprising the plaintext and the random value.

4 : The decoding apparatus according to claim 1 or 2 , wherein
the first ciphertext comprises a value obtained by encrypting a value corresponding to or deriving from information comprising the plaintext, and
the addition value comprises a value corresponding to or deriving from information comprising the first ciphertext and a random value.

5 : The decoding apparatus according to claim 1 or 2 , wherein
the first ciphertext is a value obtained by encrypting a value corresponding to or deriving from information comprising the plaintext and a random value, and
the addition value is a value corresponding to or deriving from information comprising the random value.

6 : A decoding capability providing apparatus comprising:
a storage configured to hold a decoding key for decoding first ciphertext which can be decoded by homomorphic operation; and a decoding capability provider configured to obtain information corresponding to or deriving from the first ciphertext from a decoding apparatus which performs non-homomorphic operation using a value corresponding to or deriving from a decoding value of the first ciphertext and an addition value to output plaintext, and output information to be used by the decoding apparatus to obtain the decoding value of the first ciphertext by self-correcting processing to the decoding apparatus using the decoding key without providing information of the decoding key to the decoding apparatus.

7 : The decoding capability providing apparatus according to claim 6 , wherein
the plaintext is a decoding value of second ciphertext corresponding to or deriving from information comprising the first ciphertext, the first ciphertext is OW-CPA secure for the decoding value of the first ciphertext, and the second ciphertext is IND-CCA secure for the plaintext.

8 : The decoding capability providing apparatus according to claim 6 or 7 , wherein
the first ciphertext comprises a value obtained by encrypting a value corresponding to or deriving from a random value, and
the addition value comprises a value corresponding to or deriving from information comprising the plaintext and the random value.

9 : The decoding capability providing apparatus according to claim 6 or 7 , wherein
the first ciphertext comprises a value obtained by encrypting a value corresponding to or deriving from information comprising the plaintext, and
the addition value comprises a value corresponding to or deriving from information comprising the first ciphertext and a random value.

10 : The decoding capability providing apparatus according to claim 6 or 7 , wherein
the first ciphertext comprises a value obtained by encrypting a value corresponding to or deriving from information comprising the plaintext and a random value, and
the addition value comprises a value corresponding to or deriving from information comprising the random value.

11 : A decoding method comprising:
a step of performing self-correcting processing with a decoding capability providing apparatus holding a decoding key for decoding first ciphertext which can be decoded by homomorphic operation to obtain a decoding value of the first ciphertext at a self-correcting processor; and a step of performing non-homomorphic operation using a value corresponding to or deriving from the decoding value of the first ciphertext and an addition value to output plaintext at a non-homomorphic processor.

12 : A decoding capability providing method comprising:
a step of obtaining information corresponding to first ciphertext from a decoding apparatus which performs non-homomorphic operation using a value corresponding to or deriving from a decoding value of the first ciphertext which can be decoded by homomorphic operation and an addition value to output plaintext at a decoding capability provider; and a step of outputting information to be used by the decoding apparatus to obtain the decoding value of the first ciphertext by self-correcting processing to the decoding apparatus using a decoding key for decoding the first ciphertext without providing information of the decoding key to the decoding apparatus at the decoding capability provider.

13 : A non-transitory computer-readable recording medium having stored thereon a program for causing a computer to function as the decoding apparatus according to claim 1 or 2 .

14 : A non-transitory computer-readable recording medium having stored thereon a program for causing a computer to function as the decoding capability providing apparatus according to claim 6 or 7 .

Assignees

• Nippon Telegraph And Lelephone Corp
• Nippon Telegraph & Telephone

Inventors

• Yoshida Roe
• Yamamoto Go
• Kobayashi Tetsutaro

Classifications

• H04L2209/76

  Proxy, i.e. using intermediary entity to perform cryptographic operations · CPC title

• H04L9/0819

  Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) (network architectures or network communication protocols for key distribution in a packet data network H04L63/062) · CPC title

• H04L9/008

  involving homomorphic 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

• H04L2209/60

  Digital content management, e.g. content distribution · CPC title