protect the RSA operation from timing
RSA is vulnerable to timing attacks. In a setup where attackers can measure the time of RSA decryption or signature operations, blinding must be used to protect the RSA operation from that attack.
turns blinding on for key rsa and generates a random
blinding factor. ctx is
or a pre-allocated and initialized BN_CTX.
turns blinding off and frees the memory used for the blinding factor.
RSA_blinding_on() returns 1 on success,
and 0 if an error occurred.
RSA_blinding_off() first appeared in SSLeay 0.9.0
and have been available since OpenBSD 2.4.