diff options
Diffstat (limited to 'third_party/abseil-cpp/absl/random/internal/randen_traits.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/random/internal/randen_traits.h | 33 |
1 files changed, 4 insertions, 29 deletions
diff --git a/third_party/abseil-cpp/absl/random/internal/randen_traits.h b/third_party/abseil-cpp/absl/random/internal/randen_traits.h index 120022c9fb..2b8bbe7383 100644 --- a/third_party/abseil-cpp/absl/random/internal/randen_traits.h +++ b/third_party/abseil-cpp/absl/random/internal/randen_traits.h @@ -28,29 +28,10 @@ namespace absl { ABSL_NAMESPACE_BEGIN namespace random_internal { -// RANDen = RANDom generator or beetroots in Swiss High German. +// 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 (or other random source). - // RandenTraits contains the basic algorithm traits, such as the size of the // state, seed, sponge, etc. struct RandenTraits { @@ -64,23 +45,17 @@ struct RandenTraits { // Size of the default seed consumed by the sponge. static constexpr size_t kSeedBytes = kStateBytes - kCapacityBytes; - // Assuming 128-bit blocks, the number of blocks in the state. // Largest size for which security proofs are known. static constexpr size_t kFeistelBlocks = 16; + // Type-2 generalized Feistel => one round function for every two blocks. + static constexpr size_t kFeistelFunctions = kFeistelBlocks / 2; // = 8 + // Ensures SPRP security and two full subblock diffusions. // Must be > 4 * log2(kFeistelBlocks). static constexpr size_t kFeistelRounds = 16 + 1; - - // Size of the key. A 128-bit key block is used for every-other - // feistel block (Type-2 generalized Feistel network) in each round. - static constexpr size_t kKeyBytes = 16 * kFeistelRounds * kFeistelBlocks / 2; }; -// Randen key arrays. In randen_round_keys.cc -extern const unsigned char kRandenRoundKeys[RandenTraits::kKeyBytes]; -extern const unsigned char kRandenRoundKeysBE[RandenTraits::kKeyBytes]; - } // namespace random_internal ABSL_NAMESPACE_END } // namespace absl |