64-bit integers. func ctrBlocks(b *Block, dst, src []byte, ivlo, ivhi uint64) { buf := make([]byte, len(src), 8*BlockSize) for i := 0; i < len(buf); i += BlockSize { byteorder.BEPutUint64(buf[i:], ivhi) byteorder.BEPutUint64(buf[i+8:], ivlo) ivlo, ivhi = add128(ivlo, ivhi, 1) encryptBlock(b, buf[i:], buf[i:]) } // XOR into buf first, in case src and dst overlap (see above). subtle.XORBytes(buf, src, buf) copy(dst, buf) } func add128(lo, hi uint64, x uint64) (uint64, uint64) { lo, c := bits.Add64(lo,...