Identity based universal re-encryption for mix nets

Universal Re-encryption Cryptosystems do not require the knowledge of the recipient´s public key for re-encrypting a ciphertext whereas conventional Re-encryption Cryptosystems need that knowledge. In this paper, we present the first Identity-based Universal Re-encryption Cryptosystem scheme whose re-encryption algorithm does not need to have the knowledge of the recipient´s identity. By generalizing the definition of Universal Semantic Security to Identity Based Universal Cryptosystems, we prove the security of our scheme. There are some applications for universal re-encryption cryptosystems which cannot be made using conventional cryptosystems. One significant application of these cryptosystems is in mix networks with several recipients, such as anonymous communication networks.