mac.rn

//  Copyright 2021 Google LLC.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use sponge

func computeMac(key, plaintext, macLen) {
  sponge = Sponge()
  sponge.absorb(key)
  sponge.absorb(plaintext)
  return sponge.squeeze(macLen)
}

func verifyMac(mac, key, plaintext) {
  computedMac = computeMac(key, plaintext, mac.length())
  // In most languages, this equality comparison is a major security flaw!
  // Rune does constant time comparison on secrets.
  return reveal(mac == computedMac)
}