cryptutil: move to pkg dir, add token generator (#1029)

* cryptutil: move to pkg dir, add token generator

* add gitignored files

* add tests

pkg/cryptutil/token.go

@@ -0,0 +1,68 @@
+package cryptutil
+
+import (
+	"github.com/btcsuite/btcutil/base58"
+	"github.com/google/uuid"
+)
+
+// TokenLength is the length of a token.
+const TokenLength = 16
+
+// A Token is a globally unique identifier.
+type Token [TokenLength]byte
+
+// NewRandomToken returns a new random Token (via a random UUID).
+func NewRandomToken() (tok Token) {
+	bs := uuid.New()
+	copy(tok[:], bs[:])
+	return tok
+}
+
+// TokenFromString parses a base58-encoded string into a token.
+func TokenFromString(rawstr string) (tok Token, ok bool) {
+	result := base58.Decode(rawstr)
+	if len(result) != TokenLength {
+		return tok, false
+	}
+	copy(tok[:], result[:TokenLength])
+	return tok, true
+}
+
+// String returns the Token as a base58-encoded string.
+func (tok Token) String() string {
+	bs := make([]byte, TokenLength)
+	copy(bs, tok[:])
+	return base58.Encode(bs)
+}
+
+// UUID returns the token as a UUID.
+func (tok Token) UUID() uuid.UUID {
+	var id uuid.UUID
+	copy(id[:], tok[:])
+	return id
+}
+
+// A SecretToken is made up of an id and a secret.
+type SecretToken struct {
+	ID     Token
+	Secret Token
+}
+
+// SecretTokenFromString parses a base58-encoded string into a secret token.
+func SecretTokenFromString(rawstr string) (tok SecretToken, ok bool) {
+	result := base58.Decode(rawstr)
+	if len(result) != TokenLength*2 {
+		return tok, false
+	}
+	copy(tok.ID[:], result[:TokenLength])
+	copy(tok.Secret[:], result[TokenLength:])
+	return tok, true
+}
+
+// String returns the SecretToken as a base58-encoded string.
+func (tok SecretToken) String() string {
+	bs := make([]byte, TokenLength*2)
+	copy(bs[:TokenLength], tok.ID[:])
+	copy(bs[TokenLength:], tok.Secret[:])
+	return base58.Encode(bs)
+}