typedef struct SilcMessageSignedPayloadStruct *SilcMessageSignedPayload;

    This context represents the SILC_MESSAGE_FLAG_SIGNED Payload which
    is used with channel messages and private messages to indicate that
    the message is digitally signed.  This payload may include the
    message sender's public key and it includes the digital signature.
    This payload MUST NOT be used in any other context except with
    channel and private message sending and reception.