Perform hostname verification following RFC 6125.
This method MUST be called after calling connect to ensure that the hostname of a remote peer has been verified.
See the OpenSSL documentation for EVP_PKEY_get_raw_private_key()
See the OpenSSL documentation for EVP_PKEY_get_raw_public_key()
Adds name with permissions mode to the tar, yielding io for writing the file. The signer is used to add a digest file using its digest_algorithm per add_file_digest and a cryptographic signature in name.sig. If the signer has no key only the checksum file is added.
Returns the digest.