Results 1 
3 of
3
Compact RoundOptimal PartiallyBlind Signatures
"... Abstract Partiallyblind signatures find many applications in the area of anonymity, such as in ecash or evoting systems. They extend classical blind signatures, with a signed message composed of two parts: a public one (common to the user and the signer) and a private one (chosen by the user, and ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Abstract Partiallyblind signatures find many applications in the area of anonymity, such as in ecash or evoting systems. They extend classical blind signatures, with a signed message composed of two parts: a public one (common to the user and the signer) and a private one (chosen by the user, and blindly signed). The signer cannot link later the messagesignature to the initial interaction with the user, among other signatures on messages with the same public part. This paper presents a oneround partiallyblind signature which achieves perfect blindness in the standard model using a Common Reference String, under classical assumptions: CDH and DLin assumptions in symmetric groups, and similar ones in asymmetric groups. This scheme is more efficient than the previous ones: reduced round complexity and communication complexity, but still weaker complexity assumptions. A great advantage is also to end up with a standard Waters signature, which is quite short. In addition, in all the previous schemes, the public part required a prior agreement between the parties on the public part of the message before running the blind signature protocol. Our protocol does not require such preprocessing: the public part can be chosen by the signer only. Our scheme even allows multiple messages provided from independent sources to be blindly signed. These messages can either be concatenated or aggregated by the signer, without learning any information about them, before returning the blind signature to the recipient. For the aggregation (addition of the messages), we provide a new result, of independent interest, about the Waters hash function over non binaryalphabets. 1
Dual System Encryption Framework in PrimeOrder Groups
 IACR Cryptology ePrint Archive
, 2015
"... We propose a new generic framework for achieving fully secure attribute based encryption (ABE) in primeorder bilinear groups. It is generic in the sense that it can be applied to ABE for arbitrary predicate. All previously available frameworks that are generic in this sense are given only in compos ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
We propose a new generic framework for achieving fully secure attribute based encryption (ABE) in primeorder bilinear groups. It is generic in the sense that it can be applied to ABE for arbitrary predicate. All previously available frameworks that are generic in this sense are given only in compositeorder bilinear groups, of which operations are known to be much less efficient than in primeorder ones for the same security level. These consist of the frameworks by Wee (TCC’14) and Attrapadung (Eurocrypt’14). Both provide abstractions of dualsystem encryption techniques introduced by Waters (Crypto’09). Our framework can be considered as a primeorder version of Attrapadung’s framework and works in a similar manner: it relies on a main component called pair encodings, and it generically compiles any secure pair encoding scheme for a predicate in consideration to a fully secure ABE scheme for that predicate. One feature of our new compiler is that although the resulting ABE schemes will be newly defined in primeorder groups, we require essentially the same security notions of pair encodings as before. Beside the security of pair encodings, our framework assumes only the Matrix DiffieHellman assumption (Escala et al., Crypto’13), which is a
Short Blind Signatures
"... Abstract Blind signatures allow users to obtain signatures on messages hidden from the signer; moreover, the signer cannot link the resulting message/signature pair to the signing session. This paper presents blind signature schemes, in which the number of interactions between the user and the signe ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Abstract Blind signatures allow users to obtain signatures on messages hidden from the signer; moreover, the signer cannot link the resulting message/signature pair to the signing session. This paper presents blind signature schemes, in which the number of interactions between the user and the signer is minimal and whose blind signatures are short. Our schemes are defined over bilinear groups and are proved secure in the commonreferencestring model without random oracles and under standard assumptions: CDH and the decisionlinear assumption. (We also give variants over asymmetric groups based on similar assumptions.) The blind signatures are Waters signatures, which consist of 2 group elements. Moreover, we instantiate partially blind signatures, where the message consists of a part hidden from the signer and a commonly known public part, and schemes achieving perfect blindness. We propose new variants of blind signatures, such as signerfriendly partially blind signatures, where the public part can be chosen by the signer without prior agreement, 3party blind signatures, as well as blind signatures on multiple aggregated messages provided by independent sources. We also extend Waters signatures to nonbinary alphabets by proving a new result on the underlying hash function.