3National Institute of Standards and Technology. SHA-2 Standard: Secure Hash Standard, FIPS PUB 180-2[S].www. itl. nist. gov/fipspubs/fip180- 2. htm.
4National Institute of Standards and Technology: HMAC Standard: The Keyed-Hash Message Authentication Code: HMAC[S]. http://csrc.nist.gov/publications/fips/fips.htm.
