Hi Uri Blumenthal, I hace started from the Intel RSAX engine, and I just wanted to use my own implementation of the rsa modular exponentiation. This project that I am working on intends to use a CUDA based implementation for modular computation. In order to post a working example here, I just replaced the CUDA part with the BN_mod_exp_mont function to reproduce the result, that is "RSA verify failure". Of course, when I use the CUDA implementation, I also get "RSA sign failure". Best regards, Dani Grosu -- View this message in context: http://openssl.6102.n7.nabble.com/OpenSSL-RSA-engine-RSA-verify-failure-tp65447p65450.html Sent from the OpenSSL - User mailing list archive at Nabble.com.