Abstract.Recently the bilinear pairing such as Weil pairing or Tate pairing on elliptic curves and hyperelliptic curves have been found various applications in cryptography. Several identity-based (simply ID-based) cryptosystems using bilinear pairings of elliptic curves or hyperelliptic curves were presented. Blind signature and ring signature are very useful to provide the user's anonymity and the signer's privacy. They are playing an important role in building e-commerce. In this paper, we firstly propose an ID-based blind signature scheme and an ID-based ring signature scheme, both of which are based on the bilinear pairings. Also we analyze their security and efficiency.

Abstract. In Asiacrypt2001, Boneh, Lynn, and Shacham [8] proposed a short signature scheme (BLS scheme) using bilinear pairing on certain elliptic and hyperelliptic curves. Subsequently numerous cryptographic schemes based on BLS signature scheme were proposed. BLS short signature needs a special hash function [6,1,8]. This hash function is probabilistic and generally inefficient. In this paper, we propose a new short signature scheme from the bilinear pairings that unlike BLS, uses general cryptographic hash functions such as SHA-1 or MD5, and does not require special hash functions. Furthermore, the scheme requires less pairing operations than BLS scheme and so is more efficient than BLS scheme. We use this signature scheme to construct a ring signature scheme and a new method for delegation. We give the security proofs for the new signature scheme and the ring signature scheme in the random oracle model.

No abstract

No abstract

ID-based public key systems allow the user to use his/her identity as the public key, which can simplify key management procedure compared with CA-based public key systems. However, there is an inherent disadvantage in such systems: the problem of private key escrow, i.e., the "trusted" Private Key Generator (PKG) can easily impersonate any user at any time without being detected. Although the problem of escrowing the private key may be reduced by distributing the trust onto multiple centers, it will decrease the efficiency of the systems. Chen et al. first proposed a novel ID-based signature scheme without trusted PKG from bilinear pairings [10], i.e., there is only one PKG who is not assumed to be honest in their scheme. However, the signature scheme cannot be extended to a threshold one. In this paper we propose another ID-based signature scheme without trusted PKG from bilinear pairings. Moreover, we propose an ID-based threshold signature scheme without trusted PKG, which simultaneously overcomes the problem of key escrow and adopts the approach that the private key associated with an identity rather than the master key of PKG is shared.

No abstract

No abstract

No abstract