Power Analysis by Exploiting Chosen Message and Internal Collisions – Vulnerability of Checking Mechanism for RSA-Decryption

In this paper, we will point out a new side-channel vulnerability of cryptosystems implementation based on BRIP or square-multiply-always algorithm by exploiting specially chosen input message of order two. A recently published countermeasure, BRIP, against conventional simple power analysis (SPA) and differential power analysis (DPA) will be shown to be vulnerable to the proposed SPA in this paper. Another well known SPA countermeasure, the square-multiply-always algorithm, will also be shown to be vulnerable to this new attack. Further extension of the proposed attack is possible to develop more powerful attacks.