Initial delivery of metrics code (#81)

* Initial delivery of metrics code

* Fix build issues

* Fix build issue with go vet

vendor/golang.org/x/crypto/nacl/auth/auth.go

@@ -1,58 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-/*
-Package auth authenticates a message using a secret key.
-
-The Sum function, viewed as a function of the message for a uniform random
-key, is designed to meet the standard notion of unforgeability. This means
-that an attacker cannot find authenticators for any messages not authenticated
-by the sender, even if the attacker has adaptively influenced the messages
-authenticated by the sender. For a formal definition see, e.g., Section 2.4
-of Bellare, Kilian, and Rogaway, "The security of the cipher block chaining
-message authentication code," Journal of Computer and System Sciences 61 (2000),
-362–399; http://www-cse.ucsd.edu/~mihir/papers/cbc.html.
-
-auth does not make any promises regarding "strong" unforgeability; perhaps
-one valid authenticator can be converted into another valid authenticator for
-the same message. NaCl also does not make any promises regarding "truncated
-unforgeability."
-
-This package is interoperable with NaCl: https://nacl.cr.yp.to/auth.html.
-*/
-package auth
-
-import (
-	"crypto/hmac"
-	"crypto/sha512"
-)
-
-const (
-	// Size is the size, in bytes, of an authenticated digest.
-	Size = 32
-	// KeySize is the size, in bytes, of an authentication key.
-	KeySize = 32
-)
-
-// Sum generates an authenticator for m using a secret key and returns the
-// 32-byte digest.
-func Sum(m []byte, key *[KeySize]byte) *[Size]byte {
-	mac := hmac.New(sha512.New, key[:])
-	mac.Write(m)
-	out := new([KeySize]byte)
-	copy(out[:], mac.Sum(nil)[:Size])
-	return out
-}
-
-// Verify checks that digest is a valid authenticator of message m under the
-// given secret key. Verify does not leak timing information.
-func Verify(digest []byte, m []byte, key *[32]byte) bool {
-	if len(digest) != Size {
-		return false
-	}
-	mac := hmac.New(sha512.New, key[:])
-	mac.Write(m)
-	expectedMAC := mac.Sum(nil) // first 256 bits of 512-bit sum
-	return hmac.Equal(digest, expectedMAC[:Size])
-}