[Resource Topic] 2005/435: Concurrent Blind Signatures without Random Oracles

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Concurrent Blind Signatures without Random Oracles

Authors: Aggelos Kiayias, Hong-Sheng Zhou


We present a blind signature scheme that is efficient and provably
secure without random oracles under concurrent attacks utilizing
only four moves of short communication. The scheme is based on
elliptic curve groups for which a bilinear map exists and on
extractable and equivocable commitments. The unforgeability of the
employed signature scheme is guaranteed by the LRSW assumption
while the blindness property of our scheme is guaranteed by the
Decisional Linear Diffie-Hellman assumption.

We prove our construction secure under the above assumptions as
well as Paillier’s DCR assumption in the concurrent attack model
of Juels, Luby and Ostrovsky from Crypto ‘97 using a common
reference string. Our construction is the first efficient
construction for blind signatures in such a concurrent model
without random oracles. We present two variants of our basic
protocol: first, a blind signature scheme where blindness still
holds even if the public-key generation is maliciously controlled;
second, a blind signature scheme that incorporates a ``public-tagging’’ mechanism. This latter variant of our scheme gives rise to a partially blind signature with essentially the same efficiency and security properties as our basic scheme.

ePrint: https://eprint.iacr.org/2005/435

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