summaryrefslogtreecommitdiff
path: root/absl/random/internal/randen.cc
diff options
context:
space:
mode:
Diffstat (limited to 'absl/random/internal/randen.cc')
-rw-r--r--absl/random/internal/randen.cc89
1 files changed, 89 insertions, 0 deletions
diff --git a/absl/random/internal/randen.cc b/absl/random/internal/randen.cc
new file mode 100644
index 00000000..bab8075a
--- /dev/null
+++ b/absl/random/internal/randen.cc
@@ -0,0 +1,89 @@
+// 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.
+
+#include "absl/random/internal/randen.h"
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/random/internal/randen_detect.h"
+
+// 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.
+//
+// We combine these three ideas and also change Simpira's subround keys from
+// structured/low-entropy counters to digits of Pi.
+
+namespace absl {
+namespace random_internal {
+namespace {
+
+struct RandenState {
+ const void* keys;
+ bool has_crypto;
+};
+
+RandenState GetRandenState() {
+ static const RandenState state = []() {
+ RandenState tmp;
+#if ABSL_RANDOM_INTERNAL_AES_DISPATCH
+ // HW AES Dispatch.
+ if (HasRandenHwAesImplementation() && CPUSupportsRandenHwAes()) {
+ tmp.has_crypto = true;
+ tmp.keys = RandenHwAes::GetKeys();
+ } else {
+ tmp.has_crypto = false;
+ tmp.keys = RandenSlow::GetKeys();
+ }
+#elif ABSL_HAVE_ACCELERATED_AES
+ // HW AES is enabled.
+ tmp.has_crypto = true;
+ tmp.keys = RandenHwAes::GetKeys();
+#else
+ // HW AES is disabled.
+ tmp.has_crypto = false;
+ tmp.keys = RandenSlow::GetKeys();
+#endif
+ return tmp;
+ }();
+ return state;
+}
+
+} // namespace
+
+Randen::Randen() {
+ auto tmp = GetRandenState();
+ keys_ = tmp.keys;
+#if ABSL_RANDOM_INTERNAL_AES_DISPATCH
+ has_crypto_ = tmp.has_crypto;
+#endif
+}
+
+} // namespace random_internal
+} // namespace absl