Paper 2008/354

On DDos Attack against Proxy in Re-encryption and Re-signature

Xu an Wang

Abstract

In 1998, Blaze, Bleumer, and Strauss proposed new kind of cryptographic primitives called proxy re-encryption and proxy re-signature[BBS98]. In proxy re-encryption, a proxy can transform a ciphertext computated under Alice's public key into one that can be opened under Bob's decryption key. In proxy re-signature, a proxy can transform a signature computated under Alice's secret key into one that can be verified by Bob's public key. In 2005, Ateniese et al proposed a few new re-encryption schemes and discussed its several potential applications especially in the secure distributed storage[AFGH05]. In 2006, they proposed another few re-signature schemes and also discussed its several potential applications[AH06]. They predicated that re-encryption and re-signature will play an important role in our life. Since then, researchers are sparked to give new lights to this area. Many excellent schemes have been proposed. In this paper, we introduce a new attack- DDos attack against proxy in the proxy re-cryptography. Although this attack can also be implemented against other cryptographic primitives, the danger caused by it in proxy re-cryptography seems more serious. We revisit the current literature, paying attention on their resisting DDos attack ability. We suggest a solution to decline the impact of DDos attacking. Also we give a new efficient re-encryption scheme which can achieve CCA2 secure based on Cramer-Shoup encryption scheme and prove its security. We point out this is the most efficient proxy re-encryption schemes for the proxy which can achieve CCA2 secure in the literature. At last we give our conclusions with hoping researchers give more attention on this attack.