)
// FIPS 198-1:
-// http://csrc.nist.gov/publications/fips/fips198-1/FIPS-198-1_final.pdf
+// https://csrc.nist.gov/publications/fips/fips198-1/FIPS-198-1_final.pdf
// key is zero padded to the block size of the hash function
// ipad = 0x36 byte repeated for key length