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Diffstat (limited to 'third_party/abseil_cpp/absl/random/internal/randen_traits.h')
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1 files changed, 88 insertions, 0 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 new file mode 100644 index 000000000000..53caa936140a --- /dev/null +++ b/third_party/abseil_cpp/absl/random/internal/randen_traits.h @@ -0,0 +1,88 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_ +#define ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_ + +// HERMETIC NOTE: The randen_hwaes target must not introduce duplicate +// symbols from arbitrary system and other headers, since it may be built +// with different flags from other targets, using different levels of +// optimization, potentially introducing ODR violations. + +#include <cstddef> + +#include "absl/base/config.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace random_internal { + +// 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 { + // Size of the entire sponge / state for the randen PRNG. + static constexpr size_t kStateBytes = 256; // 2048-bit + + // Size of the 'inner' (inaccessible) part of the sponge. Larger values would + // require more frequent calls to RandenGenerate. + static constexpr size_t kCapacityBytes = 16; // 128-bit + + // 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; + + // 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 + +#endif // ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_ |