int RSA_blinding_on(RSA *rsa, BN_CTX *ctx);
void RSA_blinding_off(RSA *rsa);
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.
RSA_blinding_on() turns blinding on for key rsa and generates a random blinding factor. ctx is NULL or a pre-allocated and initialized BN_CTX. The random number generator must be seeded prior to calling RSA_blinding_on().
RSA_blinding_off() 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() returns no value.