Blockwise Adversarial Model for On-line Ciphers and Symmetric Encryption Schemes

Abstract. This paper formalizes the security adversarial games for online symmetric cryptosystems in a unified framework for deterministic and probabilistic encryption schemes. On-line encryption schemes allow to encrypt messages even if the whole message is not known at the beginning of the encryption. The new introduced adversaries better capture the on-line properties than classical ones. Indeed, in the new model, the adversaries are allowed to send messages block-by-block to the encryption machine and receive the corresponding ciphertext blocks on-the-fly. This kind of attacker is called blockwise adversary and is stronger than standard one which treats messages as atomic objects. In this paper, we compare the two adversarial models for on-line encryption schemes. For probabilistic encryption schemes, we show that security is not preserved contrary to for deterministic schemes. We prove in appendix of the full version that in this last case, the two models are polynomially equiva...

• Type: Conference
• Year: 2004
• Where: SACRYPT
• Authors: Pierre-Alain Fouque, Antoine Joux, Guillaume Poupard
• Keywords: Encryption Schemes, On-line Encryption Schemes, Probabilistic Encryption Schemes, SACRYPT 2004