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Removes `derive(Clone)` on `ChaCha*Rng*`. They date back to the original PR which added RNG support (#63). Allowing `Clone` on an RNG is problematic because the cloned RNG will have the same internal state, duplicating outputs which can be catastrophic in a cryptographic context. Instead, the `SeedableRng::from_rng` method can be used to "fork" one RNG from another, seeing a new RNG with an output from another: https://docs.rs/rand_core/0.6.2/rand_core/trait.SeedableRng.html#method.from_rng
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Allow cloning on a stream cipher or RNG is problematic because it duplicates internal states, which can lead to keystream reuse / RNG output duplication, which in cryptographic contexts can be catastrophic. Instead, for things like tests ciphers can be initialized from the same seed repeatedly, which is what this PR changes the e.g. `chacha20` tests to do. This is a much more explicit way of deliberately duplicating stream ciphers/RNGs for the purposes of testing. See also: - #220 - #461 - RustCrypto/block-modes/pull/91 - rust-random/rand#1101
tarcieri
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that referenced
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Sep 11, 2025
Allow cloning on a stream cipher or RNG is problematic because it duplicates internal states, which can lead to keystream reuse / RNG output duplication, which in cryptographic contexts can be catastrophic. Instead, for things like tests ciphers can be initialized from the same seed repeatedly, which is what this PR changes the e.g. `chacha20` tests to do. This is a much more explicit way of deliberately duplicating stream ciphers/RNGs for the purposes of testing. See also: - #220 - #461 - RustCrypto/block-modes/pull/91 - rust-random/rand#1101
tarcieri
added a commit
that referenced
this pull request
Sep 11, 2025
Allow cloning on a stream cipher or RNG is problematic because it duplicates internal states, which can lead to keystream reuse / RNG output duplication, which in cryptographic contexts can be catastrophic. Instead, for things like tests ciphers can be initialized from the same seed repeatedly, which is what this PR changes the e.g. `chacha20` tests to do. This is a much more explicit way of deliberately duplicating stream ciphers/RNGs for the purposes of testing. See also: - #220 - #461 - RustCrypto/block-modes/pull/91 - rust-random/rand#1101
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Removes
derive(Clone)onChaCha*Rng*.They date back to the original PR which added RNG support (#63).
Allowing
Cloneon an RNG is problematic because the cloned RNG will have the same internal state, duplicating outputs which can be catastrophic in a cryptographic context.Instead, the
SeedableRng::from_rngmethod can be used to "fork" one RNG from another, seeing a new RNG with an output from another:https://docs.rs/rand_core/0.6.2/rand_core/trait.SeedableRng.html#method.from_rng