Abseil Common Libraries (C++) (grcp 依赖)
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89 lines
2.9 KiB
89 lines
2.9 KiB
// 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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#include "absl/random/internal/randen.h" |
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#include "absl/base/internal/raw_logging.h" |
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#include "absl/random/internal/randen_detect.h" |
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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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// High-level summary: |
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// 1) Reverie (see "A Robust and Sponge-Like PRNG with Improved Efficiency") is |
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// a sponge-like random generator that requires a cryptographic permutation. |
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// It improves upon "Provably Robust Sponge-Based PRNGs and KDFs" by |
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// achieving backtracking resistance with only one Permute() per buffer. |
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// |
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// 2) "Simpira v2: A Family of Efficient Permutations Using the AES Round |
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// Function" constructs up to 1024-bit permutations using an improved |
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// Generalized Feistel network with 2-round AES-128 functions. This Feistel |
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// block shuffle achieves diffusion faster and is less vulnerable to |
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// sliced-biclique attacks than the Type-2 cyclic shuffle. |
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// |
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// 3) "Improving the Generalized Feistel" and "New criterion for diffusion |
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// property" extends the same kind of improved Feistel block shuffle to 16 |
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// branches, which enables a 2048-bit permutation. |
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// |
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// We combine these three ideas and also change Simpira's subround keys from |
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// structured/low-entropy counters to digits of Pi. |
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namespace absl { |
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namespace random_internal { |
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namespace { |
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struct RandenState { |
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const void* keys; |
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bool has_crypto; |
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}; |
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RandenState GetRandenState() { |
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static const RandenState state = []() { |
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RandenState tmp; |
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#if ABSL_RANDOM_INTERNAL_AES_DISPATCH |
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// HW AES Dispatch. |
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if (HasRandenHwAesImplementation() && CPUSupportsRandenHwAes()) { |
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tmp.has_crypto = true; |
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tmp.keys = RandenHwAes::GetKeys(); |
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} else { |
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tmp.has_crypto = false; |
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tmp.keys = RandenSlow::GetKeys(); |
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} |
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#elif ABSL_HAVE_ACCELERATED_AES |
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// HW AES is enabled. |
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tmp.has_crypto = true; |
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tmp.keys = RandenHwAes::GetKeys(); |
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#else |
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// HW AES is disabled. |
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tmp.has_crypto = false; |
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tmp.keys = RandenSlow::GetKeys(); |
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#endif |
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return tmp; |
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}(); |
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return state; |
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} |
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} // namespace |
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Randen::Randen() { |
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auto tmp = GetRandenState(); |
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keys_ = tmp.keys; |
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#if ABSL_RANDOM_INTERNAL_AES_DISPATCH |
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has_crypto_ = tmp.has_crypto; |
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#endif |
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} |
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} // namespace random_internal |
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} // namespace absl
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