func (pka PublicKeyAlgorithm) CanSign() bool {
	switch pka {
	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA:
		return true
	}
	return false
}
func (pka PublicKeyAlgorithm) CanSign() bool {
	switch pka {
	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA:
		return true
	}
	return false
}
// CanSign returns true if it's possible for a public key of the given type to
// sign a message.