Current public key cryptographic algorithms (RSA, DSA, ECDSA) can be threaten by side channel analyses. The main approach to counter-act such attacks consists in randomizing sensitive data and address bits used in loads and stores of an exponentiation algorithm. In this paper we study a recent counter-measure "Boolean split exponent" (Tunstall et al. 2018) preventing differential power analysis on address bits. We show that one of their proposed protections has a flaw. We derive an attack exploiting this flaw and we successfully apply it on a simulated power consumption of an RSA modular exponentiation.