Exhaustive single bit fault analysis. A use case against Mbedtls and OpenSSL’s protection on ARM and Intel CPU

Abstract

Faults in software implementations target both data and instructions at different locations. Bellcore attack is a well-known fault attack that is able to break CRT-RSA. In response, cryptographic libraries such as OpenSSL are designed with protection. In this paper, new faults locations are shown on OpenSSL implementation of the CRT-RSA signature running on Intel and ARM processors. Among those faults, one restores the Bellcore attack on the OpenSSL library despite a protection and another is a complete new fault that exploits the OpenSSL protection to get RSA private key. Quite surprisingly, one of the exhibited faults is, ironically enough, made possible because of the existence of such protection. Mbedtls library is also analyzed in this paper. A way to find all exploitable faults on monobit flip fault model is also detailed.