mac := hmac.New(sha256.New, extKey)
	mac.Write([]byte(Context))
	mac.Write(nonce[:])
	mac.Sum(key[:0])
	return key
}

// GenerateIV generates a new random 256 bit IV from the provided source
// of randomness. If random is nil the default PRNG of the system
// (crypto/rand) is used.
func GenerateIV(random io.Reader) (iv [32]byte) {
	if random == nil {
		random = rand.Reader
	}
	if _, err := io.ReadFull(random, iv[:]); err != nil {

	defer func(l bool) { logger.DisableLog = l }(logger.DisableLog)
	logger.DisableLog = true

	for i, test := range generateIVTests {
		i, test := i, test
		func() {
			defer recoverTest(i, test.ShouldPass, t)
			iv := GenerateIV(test.Random)
			if iv == [32]byte{} {
				t.Errorf("Test %d: generated IV is zero IV", i) // check that we generate random and unique IV
			}
		}()
	}
}

var sealUnsealKeyTests = []struct {