private static byte[] hexStringToByteArray(final String s) {
    int len = s.length();
    byte[] data = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
      data[i / 2] =
          (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
    }
    return data;
  }
Test vectors adapted from
https://github.com/keep-network/blake2b/blob/master/compression/f_test.go
crypto/algorithms/src/test/java/org/hyperledger/besu/crypto/Blake2bfMessageDigestTest.java