diff options
Diffstat (limited to 'absl/random/internal/randen_slow.cc')
| -rw-r--r-- | absl/random/internal/randen_slow.cc | 197 |
1 files changed, 74 insertions, 123 deletions
diff --git a/absl/random/internal/randen_slow.cc b/absl/random/internal/randen_slow.cc index 8d074582..4e5f3dc1 100644 --- a/absl/random/internal/randen_slow.cc +++ b/absl/random/internal/randen_slow.cc @@ -20,6 +20,7 @@ #include "absl/base/attributes.h" #include "absl/random/internal/platform.h" +#include "absl/random/internal/randen_traits.h" #if ABSL_HAVE_ATTRIBUTE(always_inline) || \ (defined(__GNUC__) && !defined(__clang__)) @@ -225,35 +226,16 @@ constexpr uint32_t te3[256] = { 0xb0b0cb7b, 0x5454fca8, 0xbbbbd66d, 0x16163a2c, }; -struct alignas(16) u64x2 { - constexpr u64x2() : v{0, 0} {}; - constexpr u64x2(uint64_t hi, uint64_t lo) : v{lo, hi} {} - - uint64_t v[2]; -}; - // Software implementation of the Vector128 class, using uint32_t // as an underlying vector register. -// -struct Vector128 { - inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE Vector128& operator^=( - const Vector128& other) { - s[0] ^= other.s[0]; - s[1] ^= other.s[1]; - s[2] ^= other.s[2]; - s[3] ^= other.s[3]; - return *this; - } - +struct alignas(16) Vector128 { uint32_t s[4]; }; inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE Vector128 -Vector128Load(const void* ABSL_RANDOM_INTERNAL_RESTRICT from) { +Vector128Load(const void* from) { Vector128 result; - const uint8_t* ABSL_RANDOM_INTERNAL_RESTRICT src = - reinterpret_cast<const uint8_t*>(from); - + const uint8_t* src = reinterpret_cast<const uint8_t*>(from); result.s[0] = static_cast<uint32_t>(src[0]) << 24 | static_cast<uint32_t>(src[1]) << 16 | static_cast<uint32_t>(src[2]) << 8 | @@ -274,7 +256,7 @@ Vector128Load(const void* ABSL_RANDOM_INTERNAL_RESTRICT from) { } inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void Vector128Store( - const Vector128& v, void* ABSL_RANDOM_INTERNAL_RESTRICT to) { + const Vector128& v, void* to) { uint8_t* dst = reinterpret_cast<uint8_t*>(to); dst[0] = static_cast<uint8_t>(v.s[0] >> 24); dst[1] = static_cast<uint8_t>(v.s[0] >> 16); @@ -298,91 +280,57 @@ inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void Vector128Store( // symmetry of AES (ensures previously equal columns differ afterwards). inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE Vector128 AesRound(const Vector128& state, const Vector128& round_key) { - // clang-format off Vector128 result; - result.s[0] = round_key.s[0] ^ - te0[uint8_t(state.s[0] >> 24)] ^ - te1[uint8_t(state.s[1] >> 16)] ^ - te2[uint8_t(state.s[2] >> 8)] ^ + result.s[0] = round_key.s[0] ^ // + te0[uint8_t(state.s[0] >> 24)] ^ // + te1[uint8_t(state.s[1] >> 16)] ^ // + te2[uint8_t(state.s[2] >> 8)] ^ // te3[uint8_t(state.s[3])]; - result.s[1] = round_key.s[1] ^ - te0[uint8_t(state.s[1] >> 24)] ^ - te1[uint8_t(state.s[2] >> 16)] ^ - te2[uint8_t(state.s[3] >> 8)] ^ + result.s[1] = round_key.s[1] ^ // + te0[uint8_t(state.s[1] >> 24)] ^ // + te1[uint8_t(state.s[2] >> 16)] ^ // + te2[uint8_t(state.s[3] >> 8)] ^ // te3[uint8_t(state.s[0])]; - result.s[2] = round_key.s[2] ^ - te0[uint8_t(state.s[2] >> 24)] ^ - te1[uint8_t(state.s[3] >> 16)] ^ - te2[uint8_t(state.s[0] >> 8)] ^ + result.s[2] = round_key.s[2] ^ // + te0[uint8_t(state.s[2] >> 24)] ^ // + te1[uint8_t(state.s[3] >> 16)] ^ // + te2[uint8_t(state.s[0] >> 8)] ^ // te3[uint8_t(state.s[1])]; - result.s[3] = round_key.s[3] ^ - te0[uint8_t(state.s[3] >> 24)] ^ - te1[uint8_t(state.s[0] >> 16)] ^ - te2[uint8_t(state.s[1] >> 8)] ^ + result.s[3] = round_key.s[3] ^ // + te0[uint8_t(state.s[3] >> 24)] ^ // + te1[uint8_t(state.s[0] >> 16)] ^ // + te2[uint8_t(state.s[1] >> 8)] ^ // te3[uint8_t(state.s[2])]; return result; - // clang-format on } -// RANDen = RANDom generator or beetroots in Swiss German. -// 'Strong' (well-distributed, unpredictable, backtracking-resistant) random -// generator, faster in some benchmarks than std::mt19937_64 and pcg64_c32. -// -// High-level summary: -// 1) Reverie (see "A Robust and Sponge-Like PRNG with Improved Efficiency") is -// a sponge-like random generator that requires a cryptographic permutation. -// It improves upon "Provably Robust Sponge-Based PRNGs and KDFs" by -// achieving backtracking resistance with only one Permute() per buffer. -// -// 2) "Simpira v2: A Family of Efficient Permutations Using the AES Round -// Function" constructs up to 1024-bit permutations using an improved -// Generalized Feistel network with 2-round AES-128 functions. This Feistel -// block shuffle achieves diffusion faster and is less vulnerable to -// sliced-biclique attacks than the Type-2 cyclic shuffle. -// -// 3) "Improving the Generalized Feistel" and "New criterion for diffusion -// property" extends the same kind of improved Feistel block shuffle to 16 -// branches, which enables a 2048-bit permutation. -// -// Combine these three ideas and also change Simpira's subround keys from -// structured/low-entropy counters to digits of Pi. - -// Randen constants. -constexpr size_t kFeistelBlocks = 16; -constexpr size_t kFeistelFunctions = kFeistelBlocks / 2; // = 8 -constexpr size_t kFeistelRounds = 16 + 1; // > 4 * log2(kFeistelBlocks) -constexpr size_t kKeys = kFeistelRounds * kFeistelFunctions; - -// INCLUDE keys. -#include "absl/random/internal/randen-keys.inc" - -static_assert(kKeys == kRoundKeys, "kKeys and kRoundKeys must be equal"); +using ::absl::random_internal::RandenTraits; -// 2 uint64_t lanes per Vector128 -static constexpr size_t kLanes = 2; +// Randen operates on 128-bit vectors. +struct alignas(16) u64x2 { + uint64_t data[2]; +}; // The improved Feistel block shuffle function for 16 blocks. inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void BlockShuffle( - uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT state_u64) { - static_assert(kFeistelBlocks == 16, + u64x2* state) { + static_assert(RandenTraits::kFeistelBlocks == 16, "Feistel block shuffle only works for 16 blocks."); - constexpr size_t shuffle[kFeistelBlocks] = {7, 2, 13, 4, 11, 8, 3, 6, - 15, 0, 9, 10, 1, 14, 5, 12}; - - u64x2* ABSL_RANDOM_INTERNAL_RESTRICT state = - reinterpret_cast<u64x2*>(state_u64); + constexpr size_t shuffle[RandenTraits::kFeistelBlocks] = { + 7, 2, 13, 4, 11, 8, 3, 6, 15, 0, 9, 10, 1, 14, 5, 12}; // The fully unrolled loop without the memcpy improves the speed by about - // 30% over the equivalent (leaving code here as a comment): - if (false) { - u64x2 source[kFeistelBlocks]; - std::memcpy(source, state, sizeof(source)); - for (size_t i = 0; i < kFeistelBlocks; i++) { - const u64x2 v0 = source[shuffle[i]]; - state[i] = v0; - } + // 30% over the equivalent: +#if 0 + u64x2 source[RandenTraits::kFeistelBlocks]; + std::memcpy(source, state, sizeof(source)); + for (size_t i = 0; i < RandenTraits::kFeistelBlocks; i++) { + const u64x2 v0 = source[shuffle[i]]; + state[i] = v0; } + return; +#endif const u64x2 v0 = state[shuffle[0]]; const u64x2 v1 = state[shuffle[1]]; @@ -424,23 +372,23 @@ inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void BlockShuffle( // parallel hides the 7-cycle AESNI latency on HSW. Note that the Feistel // XORs are 'free' (included in the second AES instruction). inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE const u64x2* FeistelRound( - uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT state, + u64x2* ABSL_RANDOM_INTERNAL_RESTRICT state, const u64x2* ABSL_RANDOM_INTERNAL_RESTRICT keys) { - for (size_t branch = 0; branch < kFeistelBlocks; branch += 4) { - const Vector128 s0 = Vector128Load(state + kLanes * branch); - const Vector128 s1 = Vector128Load(state + kLanes * (branch + 1)); + for (size_t branch = 0; branch < RandenTraits::kFeistelBlocks; branch += 4) { + const Vector128 s0 = Vector128Load(state + branch); + const Vector128 s1 = Vector128Load(state + branch + 1); const Vector128 f0 = AesRound(s0, Vector128Load(keys)); keys++; const Vector128 o1 = AesRound(f0, s1); - Vector128Store(o1, state + kLanes * (branch + 1)); + Vector128Store(o1, state + branch + 1); // Manually unroll this loop once. about 10% better than not unrolled. - const Vector128 s2 = Vector128Load(state + kLanes * (branch + 2)); - const Vector128 s3 = Vector128Load(state + kLanes * (branch + 3)); + const Vector128 s2 = Vector128Load(state + branch + 2); + const Vector128 s3 = Vector128Load(state + branch + 3); const Vector128 f2 = AesRound(s2, Vector128Load(keys)); keys++; const Vector128 o3 = AesRound(f2, s3); - Vector128Store(o3, state + kLanes * (branch + 3)); + Vector128Store(o3, state + branch + 3); } return keys; } @@ -450,11 +398,9 @@ inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE const u64x2* FeistelRound( // 2^64 queries if the round function is a PRF. This is similar to the b=8 case // of Simpira v2, but more efficient than its generic construction for b=16. inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void Permute( - const void* keys, uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT state) { - const u64x2* ABSL_RANDOM_INTERNAL_RESTRICT keys128 = - static_cast<const u64x2*>(keys); - for (size_t round = 0; round < kFeistelRounds; ++round) { - keys128 = FeistelRound(state, keys128); + u64x2* state, const u64x2* ABSL_RANDOM_INTERNAL_RESTRICT keys) { + for (size_t round = 0; round < RandenTraits::kFeistelRounds; ++round) { + keys = FeistelRound(state, keys); BlockShuffle(state); } } @@ -468,37 +414,42 @@ namespace random_internal { const void* RandenSlow::GetKeys() { // Round keys for one AES per Feistel round and branch. // The canonical implementation uses first digits of Pi. - return round_keys; + return kRandenRoundKeys; } void RandenSlow::Absorb(const void* seed_void, void* state_void) { - uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT state = - reinterpret_cast<uint64_t*>(state_void); - const uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT seed = - reinterpret_cast<const uint64_t*>(seed_void); - - constexpr size_t kCapacityBlocks = kCapacityBytes / sizeof(uint64_t); - static_assert(kCapacityBlocks * sizeof(uint64_t) == kCapacityBytes, - "Not i*V"); - for (size_t i = kCapacityBlocks; i < kStateBytes / sizeof(uint64_t); ++i) { + auto* state = + reinterpret_cast<uint64_t * ABSL_RANDOM_INTERNAL_RESTRICT>(state_void); + const auto* seed = + reinterpret_cast<const uint64_t * ABSL_RANDOM_INTERNAL_RESTRICT>( + seed_void); + + constexpr size_t kCapacityBlocks = + RandenTraits::kCapacityBytes / sizeof(uint64_t); + static_assert( + kCapacityBlocks * sizeof(uint64_t) == RandenTraits::kCapacityBytes, + "Not i*V"); + + for (size_t i = kCapacityBlocks; + i < RandenTraits::kStateBytes / sizeof(uint64_t); ++i) { state[i] ^= seed[i - kCapacityBlocks]; } } -void RandenSlow::Generate(const void* keys, void* state_void) { - static_assert(kCapacityBytes == sizeof(Vector128), "Capacity mismatch"); +void RandenSlow::Generate(const void* keys_void, void* state_void) { + static_assert(RandenTraits::kCapacityBytes == sizeof(u64x2), + "Capacity mismatch"); - uint64_t* ABSL_RANDOM_INTERNAL_RESTRICT state = - reinterpret_cast<uint64_t*>(state_void); + auto* state = reinterpret_cast<u64x2*>(state_void); + const auto* keys = reinterpret_cast<const u64x2*>(keys_void); - const Vector128 prev_inner = Vector128Load(state); + const u64x2 prev_inner = state[0]; - Permute(keys, state); + Permute(state, keys); // Ensure backtracking resistance. - Vector128 inner = Vector128Load(state); - inner ^= prev_inner; - Vector128Store(inner, state); + state[0].data[0] ^= prev_inner.data[0]; + state[0].data[1] ^= prev_inner.data[1]; } } // namespace random_internal |