Simple Power Analysis Attack on the QC-LDPC McEliece Cryptosystem

It is known that a naive implementation of the decryption algorithm in the McEliece cryptosystem allows an attacker to recover the secret matrix P by measuring the power consumption. We demonstrate that a similar threat is present in the QC-LDPC variant of the McEliece cryptosystem. We consider a naive implementation of the decryption algorithm in the QC-LDPC McEliece cryptosystem. We demonstrate that this implementation leaks information about positions of ones in the secret matrix Q. We argue that this leakage allows an attacker to completely recover the matrix Q. In addition, we note that the quasi-cyclic nature of the matrix Q allows to accelerate the attack significantly.