From b56cbdd23834a65682c0b46f367f8679e83bc894 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 18 Sep 2020 15:55:15 -0700 Subject: Abseil LTS 20200923 What's New: * `absl::StatusOr` 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 --- absl/random/internal/randen_traits.h | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) (limited to 'absl/random/internal/randen_traits.h') 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 -- cgit v1.2.3