Go treats underscores specially

In case there's ever a platform called helpers or protocol, we don't
want to be doing this.

noise-types.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"crypto/subtle"
+	"encoding/hex"
+	"errors"
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+const (
+	NoisePublicKeySize  = 32
+	NoisePrivateKeySize = 32
+)
+
+type (
+	NoisePublicKey    [NoisePublicKeySize]byte
+	NoisePrivateKey   [NoisePrivateKeySize]byte
+	NoiseSymmetricKey [chacha20poly1305.KeySize]byte
+	NoiseNonce        uint64 // padded to 12-bytes
+)
+
+func loadExactHex(dst []byte, src string) error {
+	slice, err := hex.DecodeString(src)
+	if err != nil {
+		return err
+	}
+	if len(slice) != len(dst) {
+		return errors.New("Hex string does not fit the slice")
+	}
+	copy(dst, slice)
+	return nil
+}
+
+func (key NoisePrivateKey) IsZero() bool {
+	var zero NoisePrivateKey
+	return key.Equals(zero)
+}
+
+func (key NoisePrivateKey) Equals(tar NoisePrivateKey) bool {
+	return subtle.ConstantTimeCompare(key[:], tar[:]) == 1
+}
+
+func (key *NoisePrivateKey) FromHex(src string) error {
+	return loadExactHex(key[:], src)
+}
+
+func (key NoisePrivateKey) ToHex() string {
+	return hex.EncodeToString(key[:])
+}
+
+func (key *NoisePublicKey) FromHex(src string) error {
+	return loadExactHex(key[:], src)
+}
+
+func (key NoisePublicKey) ToHex() string {
+	return hex.EncodeToString(key[:])
+}
+
+func (key NoisePublicKey) IsZero() bool {
+	var zero NoisePublicKey
+	return key.Equals(zero)
+}
+
+func (key NoisePublicKey) Equals(tar NoisePublicKey) bool {
+	return subtle.ConstantTimeCompare(key[:], tar[:]) == 1
+}
+
+func (key *NoiseSymmetricKey) FromHex(src string) error {
+	return loadExactHex(key[:], src)
+}
+
+func (key NoiseSymmetricKey) ToHex() string {
+	return hex.EncodeToString(key[:])
+}