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, 29 insertions, 4 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 2b8bbe7383..120022c9fb 100644 --- a/third_party/abseil-cpp/absl/random/internal/randen_traits.h +++ b/third_party/abseil-cpp/absl/random/internal/randen_traits.h @@ -28,10 +28,29 @@ namespace absl { ABSL_NAMESPACE_BEGIN namespace random_internal { -// RANDen = RANDom generator or beetroots in Swiss German. +// RANDen = RANDom generator or beetroots in Swiss High 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 { @@ -45,17 +64,23 @@ 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 |