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fix(wallet-core): confirm and pin provision_wallet's entropy source as a CSPRNG - #381
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Emmyt24 merged 2 commits intoSep 28, 2026
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…s a CSPRNG provision_wallet's mnemonic generation depended transitively on tiny-bip39's Mnemonic::new, which draws entropy from rand::thread_rng() only when the crate's default `rand` feature is enabled. Generate the 128-bit entropy from OsRng explicitly and build the mnemonic with Mnemonic::from_entropy, so the guarantee no longer rests on a dependency default. Documents the source on WalletSeed::generate, in Cargo.toml and in docs/architecture.md, and adds a collision smoke test. Closes Octo-Protocol-org#319
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…re/audit-provision-entropy-source # Conflicts: # crates/wallet-core/src/derive.rs # docs/architecture.md
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Closes #319
Audit finding
Call chain before this PR (tiny-bip39 2.0.0, rand 0.8.5 per
Cargo.lock):provision_wallet(crates/wallet-core/src/provision.rs) →WalletSeed::generate()WalletSeed::generate()→bip39::Mnemonic::new(MnemonicType::Words12, …)tiny-bip39-2.0.0/src/mnemonic.rs:66Mnemonic::new(#[cfg(feature = "rand")]) →crypto::gen_random_bytes(16)tiny-bip39-2.0.0/src/crypto.rs:24gen_random_bytes→rand::thread_rng().fill_bytes(..)ThreadRng= ChaCha12 block RNG, seeded and periodically reseeded fromOsRng.So the source was a CSPRNG. But the guarantee was implicit: it only exists while tiny-bip39's default
randfeature is on, and the algorithm is arandimplementation detail that a version bump could change without anyone noticing.Change
WalletSeed::generate()now fills 16 bytes of entropy fromrand::rngs::OsRng(getrandom(2)), zeroizes the buffer, and builds the mnemonic withMnemonic::from_entropy.Mnemonic::newis no longer called.WalletSeed::generate()records the source, plus a doc-test.Cargo.toml(tiny-bip39,rand),crates/wallet-core/Cargo.toml, anddocs/architecture.md("Entropy source (load-bearing)").Tests
generated_mnemonics_never_collide_across_a_large_sample: draws 10,000 mnemonics with no collision, then checks that two fullgenerate()calls differ. This is a smoke test, not a randomness-quality audit.WalletSeed::generate.cargo test -p octo-wallet-core: all pass.