code: func KeyDigestEquals(j, k crypto.PublicKey) bool {
  	digestJ, errJ := KeyDigest(j)
  	digestK, errK := KeyDigest(k)
  	// Keys that don't have a valid digest (due to marshalling problems)
  	// are never equal. So, e.g. nil keys are not equal.
  	if errJ != nil || errK != nil {
  		return false
  	}
  	return digestJ == digestK
  }
docs: // KeyDigestEquals determines whether two public keys have the same digest.