Cryptographic system for group signature
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Abstract
The invention concerns a system enabling a member (M) of a group (G) to produce, by means of customized data (z; K), a message (m) accompanied by a signature (8) proving to a verifier that the message originates from a member of the group (G). The invention is characterized in that the customized data is in the form of an electronic physical medium (26). Advantageously, the latter also incorporates: encrypting means (B3) for producing a customized cipher (C) from the customized data prior to the signature S of the message (m), means (B5) for producing a combination of a message m to be signed and the cipher (C) associated with said message, for example in the form of a concatenation of the message (m) with the cipher (C), and means (B6) for signing (Sig) the message (m) with the customized data (z; K) in the form of a cipher (C) associated with said message. Advantageously, the physical medium is a smart card (26) or the like.
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Citations
39 Claims
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1-19. -19. (canceled)
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20. A group signature system enabling a member (M) of a group (G) to produce a message (m) accompanied by a signature (S) for proving to a checker (2, 4) that the said message (m) originates from a member (M) of said group (G), using personalized data (z;
- Kz),
characterized in that said system is electronic and includes an electronic hardware support (26) and in that the said personalized data is integrated into said electronic hardware support (26). - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
- Kz),
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34. A method for checking a message (m) sent by a member (M) of a group (G) accompanied by a signature (S) wherein the message (m) authentication the signature to indicated that the message originates from a member of the group, comprises producing the signature (S) of the message (m) with a private key (SK) common to members (M) of the group (G) and integrating personalized data (z;
- KZ) electronic hardware support (26) into the message, transmitting the message with the authenticated signature to a user of the system (2,6) without needing to supply proof to the user that the member (M) belongs to the said group (G).
- View Dependent Claims (35)
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36. A method for opening a signature (S) produced by a group signature system which enables a member (M) of a group (G) to produce a message (m) accompanied by the signature (S) so as to authenticate the signature (S) for a user of the system comprising the steps of:
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making correspondence data between the identities of members (M) of the group (G) and their personalized data available, before the signature;
decrypting the personalized data received from an electronic hardware support (26) for which the signature is to be opened; and
opening the signature when the decrypted personalized data corresponds to the identity of the member (M) of the group (G).
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37. A method for adapting an electronic hardware support (26) for a group signature system which enables a member (M) of a group (G) to produce a message (m) accompanied by a signature (S) to authenticate the signature (S) for a user of the system wherein the hardware support is personalized to a member (M) of the group, characterized in that it comprises steps consisting of:
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producing personalized data (z;
Kz) to be used for the said electronic hardware support (26) to be personalized; and
registering this personalized data with a private signature key (SK) in the said hardware support.
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38. A group signature system, comprising a terminal (10), said terminal including means for reading a portable communicating device issued to a member (M) of a group by a trusted authority, said device being personalized to the member (M) with personalized data integrated into the device in the form of an identifier (z, Kz) so as to be capable of producing a message and signature associated with the group;
said device including encryption means for making a personalized encrypted text using the personalized data before the signature of the message and means for making a combination of the message to be signed and the encrypted text associated with the message in the form of a concatenation of the message and the encrypted text. - View Dependent Claims (39)
Specification