// concatenation of an MD5 and SHA1 hash.
func md5SHA1Hash(slices [][]byte) []byte {
	md5sha1 := make([]byte, md5.Size+sha1.Size)
	hmd5 := md5.New()
	for _, slice := range slices {
		hmd5.Write(slice)
	}
	copy(md5sha1, hmd5.Sum(nil))
	copy(md5sha1[md5.Size:], sha1Hash(slices))
	return md5sha1
}

// hashForServerKeyExchange hashes the given slices and returns their digest

// signature algorithm negotiation.
func legacyTypeAndHashFromPublicKey(pub crypto.PublicKey) (sigType uint8, hash crypto.Hash, err error) {
	switch pub.(type) {
	case *rsa.PublicKey:
		return signaturePKCS1v15, crypto.MD5SHA1, nil
	case *ecdsa.PublicKey:
		return signatureECDSA, crypto.SHA1, nil
	case ed25519.PublicKey:
		// RFC 8422 specifies support for Ed25519 in TLS 1.0 and 1.1,

	crypto.SHA512:    {0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05, 0x00, 0x04, 0x40},
	crypto.MD5SHA1:   {}, // A special TLS case which doesn't use an ASN1 prefix.
	crypto.RIPEMD160: {0x30, 0x20, 0x30, 0x08, 0x06, 0x06, 0x28, 0xcf, 0x06, 0x03, 0x00, 0x31, 0x04, 0x14},
}