Implement reused secret keys for Noise/X3DH/etc protocols #71
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rozbb
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Sep 14, 2021
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LGTM! I like that it's feature-gated, since this use case is kind of niche. Two notes:
- The current docs on
StaticSecretdon't contain the same "if you don't know what to use, please use EphemeralSecret" warning. I think it should, for the same reason that it appears here. I don't feel strongly about that though. - The current docs on
StaticSecretmake explicit reference to being useful for the Noise protocol. That paragraph should either be deleted or moved toReusableSecret.
src/x25519.rs
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| /// secret keys are never reused, which can have very serious security | ||
| /// implications for many protocols. | ||
| #[cfg(feature = "reusable_secrets")] | ||
| #[derive(Zeroize)] |
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Might wanna make it Clone too, just for usability sake
| } | ||
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| /// Generate a non-serializeable x25519 key. | ||
| pub fn new<T: RngCore + CryptoRng>(mut csprng: T) -> Self { |
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"Generate a non-serializable x25519 secret key."
or, copying from EphemeralSecret,
"Generate an x25519 [ReusableSecret] key."
Either one, I just think the word "secret" needs to be somewhere because "key" is ambiguous
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Thanks @rozbb! I've implemented your suggestions above. |
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This implements secret keys which are technically reusable, but discouraged from reuse due to not having serialisation methods, in order to facilitate certain keying constructs in the Noise protocol and others which require doing Diffie-Hellman operations more than once with a single somewhat-ephemeral key. (cf. #57)