Verifies a digital signature using a key.
This method verifies a digital signature using the asymmetric key version specified by KeyName and VersionId. If the signature is successfully verified, this method return , otherwise it returns .
The IsDigest parameter specifies whether the message data is the original message () or a message digest (). When a message digest is supplied, keep in mind that it must be the exact same digest that was used at signing time, regardless of whether it has been recomputed.
Google does not support server-side signature verification, so this method will call GetPublicKey internally and then use the public key to verify the digital signature locally. This functionality is offered as a convenience.