CPU + RAM friendliness CPU-friendly 32- or 64-bit integers, SIMD Sequential memory-hard functions "Large" variable S-boxes However, this prevents use of SIMD until AVX2 VSIB Use of specialized instructions - e.g., AES-NI CPU-unfriendly Small S-boxes (variable or/and fixed) - waste machine word bits Beware of bitslicing and byte permute instructions Bit permutations Such instructions are to appear in 2013 in non-SIMD form, though Unusual transforms e.g., integer addition with only partial carry (an adder with some holes punched)