Your link - which is interesting - concerns sanity check on private keys. I agree that such checks need to be implemented very carefully, since they handle high

Your link - which is interesting - concerns sanity check on private keys. I agree that such checks need to be implemented very carefully, since they handle highly-sensitive data. However, I was proposing verifying the signature - which involves only the public key and the signed data, neither of which are likely to be all that sensitive. (The situation is more subtle for RSA decryption.)