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authorGravatar Abseil Team <absl-team@google.com>2020-09-18 15:55:15 -0700
committerGravatar Derek Mauro <dmauro@google.com>2020-09-24 13:47:15 -0400
commitb56cbdd23834a65682c0b46f367f8679e83bc894 (patch)
treedacab9a64dd1a9e9668737e511d1a5420ff96001 /absl/random/internal/randen_traits.h
parentb832dce8489ef7b6231384909fd9b68d5a5ff2b7 (diff)
Abseil LTS 2020092320200923
What's New: * `absl::StatusOr<T>` has been released. See our [blog post](https://abseil.io/blog/2020-091021-status) for more information. * Abseil Flags reflection interfaces have been released. * Abseil Flags memory usage has been significantly optimized. * Abseil now supports a "hardened" build mode. This build mode enables runtime checks that guard against programming errors that may lead to security vulnerabilities. Notable Fixes: * Sanitizer dynamic annotations like `AnnotateRWLockCreate` that are also defined by the compiler sanitizer implementation are no longer also defined by Abseil. * Sanitizer macros are now prefixed with `ABSL_` to avoid naming collisions. * Sanitizer usage is now automatically detected and no longer requires macros like `ADDRESS_SANITIZER` to be defined on the command line. Breaking Changes: * Abseil no longer contains a `dynamic_annotations` library. Users using a supported build system (Bazel or CMake) are unaffected by this, but users manually specifying link libraries may get an error about a missing linker input. Baseline: 7680a5f8efe32de4753baadbd63e74e59d95bac1 Cherry picks: None
Diffstat (limited to 'absl/random/internal/randen_traits.h')
-rw-r--r--absl/random/internal/randen_traits.h31
1 files changed, 28 insertions, 3 deletions
diff --git a/absl/random/internal/randen_traits.h b/absl/random/internal/randen_traits.h
index 2b8bbe73..53caa936 100644
--- a/absl/random/internal/randen_traits.h
+++ b/absl/random/internal/randen_traits.h
@@ -32,6 +32,25 @@ namespace random_internal {
// '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