64 lines
2.3 KiB
C++
64 lines
2.3 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_
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#define ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_
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// HERMETIC NOTE: The randen_hwaes target must not introduce duplicate
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// symbols from arbitrary system and other headers, since it may be built
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// with different flags from other targets, using different levels of
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// optimization, potentially introducing ODR violations.
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#include <cstddef>
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#include "absl/base/config.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace random_internal {
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// RANDen = RANDom generator or beetroots in Swiss German.
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// 'Strong' (well-distributed, unpredictable, backtracking-resistant) random
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// generator, faster in some benchmarks than std::mt19937_64 and pcg64_c32.
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//
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// RandenTraits contains the basic algorithm traits, such as the size of the
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// state, seed, sponge, etc.
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struct RandenTraits {
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// Size of the entire sponge / state for the randen PRNG.
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static constexpr size_t kStateBytes = 256; // 2048-bit
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// Size of the 'inner' (inaccessible) part of the sponge. Larger values would
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// require more frequent calls to RandenGenerate.
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static constexpr size_t kCapacityBytes = 16; // 128-bit
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// Size of the default seed consumed by the sponge.
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static constexpr size_t kSeedBytes = kStateBytes - kCapacityBytes;
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// Largest size for which security proofs are known.
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static constexpr size_t kFeistelBlocks = 16;
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// Type-2 generalized Feistel => one round function for every two blocks.
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static constexpr size_t kFeistelFunctions = kFeistelBlocks / 2; // = 8
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// Ensures SPRP security and two full subblock diffusions.
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// Must be > 4 * log2(kFeistelBlocks).
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static constexpr size_t kFeistelRounds = 16 + 1;
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};
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} // namespace random_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_
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