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.
RETURN VALUES
RSA_blinding_on() returns 1 on success, and 0 if an error occurred.