GenRandomString returns 32 bytes of random string encoded with URL base64 encoding.

VerifyChallengeResponseSignature validates that the signature of a blob is actually signed by the corresponding certificate.

WithAgentGenerateChallengeResponseSignature generates, given the client parameters, a valid ssh signature that can be latter used to sing messages back to the server.

WithCertAndPrivateKeyGenerateChallengeResponseSignature generates similar to WithAgentGenerateChallengeResponseSignature but instead of an agent uses an explicit certifiate and keu.