Modified Parameter Attacks: Practical Attacks against CCA2 Secure Cryptosystems and Countermeasures

Abstract

We introduce the concept of Modified Parameter Attacks, a natural extension of the idea of Adapative Chosen Ciphertext Attacks (CCA2) under which some CCA2 secure systems can be shown to be insecure. These insecurities can be addressed at the application level, but can also be addressed when cryptographic schemes are being designed. We survey some existing CCA2 secure systems which are vulnerable to this attack and suggest practical countermeasures