code: func (c *ServerContext) VerifySignature(msg, token []byte, seqno uint32) (uint32, error) {
  	return verifySignature(c.sctxt, msg, token, seqno)
  }
docs: // VerifySignature uses the established server context and signature token
  // to check that the provided message hasn't been tampered or received out
  // of sequence. It returns any quality of protection flags and any error
  // that occurred.