ml-dsa: lower stack usage of KeyPair::from_seed by up to 112kb#1259
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tarcieri merged 1 commit intoRustCrypto:masterfrom Mar 20, 2026
Merged
ml-dsa: lower stack usage of KeyPair::from_seed by up to 112kb#1259tarcieri merged 1 commit intoRustCrypto:masterfrom
tarcieri merged 1 commit intoRustCrypto:masterfrom
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When using the KeyGen::from_seed is used, the A Matrix is computed (using `expand_a`). By design, the matrix is kept on the stack, and two copies end up being held (One in the `SigningKey` and another one in the `VerifyingKey`). That matrix takes up to 56kB for ML-DSA-87. Because two `SigningKey::new`/`VerifyingKey::new` code paths maybe used without the A matrix (when decoding from an expanded key), the code paths for both builder end up having to store two copies of the matrix and increases the stack size. This is all private API and does not break any of the public API. This only affects the debug/test builds as the release builds appears to optimize the unwrap_or_else and not use extraneous stack space.
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tarcieri
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When using the KeyGen::from_seed is used, the A Matrix is computed (using
expand_a).By design, the matrix is kept on the stack, and two copies end up being held (One in the
SigningKeyand another one in theVerifyingKey). That matrix takes up to 56kB for ML-DSA-87.Because two
SigningKey::new/VerifyingKey::newcode paths maybe used without the A matrix (when decoding from an expanded key), the code paths for both builder end up having to store two copies of the matrix and increases the stack size.This is all private API and does not break any of the public API.
This only affects the debug/test builds as the release builds appears to optimize the unwrap_or_else and not use extraneous stack space.
See #1024