Attacking code/lattice-based cryptosystems using Partial Knowledge

Code-based cryptographic schemes are promising candidates for post-quantum cryptography since they are fast, require only basic arithmetic, and because their security is well understood. While most analyses of security assume that an attacker does not have any information about the secret key, we show that in certain scenarios an attacker can gain partial knowledge of the secret key. We present how this knowledge can be used to improve the efficiency of an attack, and give new bounds for the complexity of such an attack. In this paper, we analyze two types of partial knowledge including concrete scenarios, and give an idea how to prevent the leak of such knowledge to an attacker.