86 lines
2.0 KiB
Rust
86 lines
2.0 KiB
Rust
#![no_std]
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//! Committing AEAD constructions. Allows one to construct key/fully committing AEAD constructions
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//! from [existing AEADs].
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//!
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//! [existing AEADS]: aead
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use core::marker::PhantomData;
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use aead::generic_array::GenericArray;
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use aead::{AeadCore, AeadInPlace, Error, KeyInit, KeySizeUser, Nonce, Tag};
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use digest::Digest;
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/// CTX key committing AEAD construction from [“On Committing Authenticated Encryption” by John Chan and Phillip Rogaway](https://eprint.iacr.org/2022/1260).
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pub struct CtxCommitment<A, H>
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where
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A: AeadCore + KeyInit,
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H: Digest,
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{
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key: GenericArray<u8, A::KeySize>,
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naead: A,
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_digest: PhantomData<H>,
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}
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impl<A, H> AeadCore for CtxCommitment<A, H>
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where
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A: AeadCore + KeyInit,
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H: Digest,
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{
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type NonceSize = A::NonceSize;
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type TagSize = H::OutputSize;
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type CiphertextOverhead = A::CiphertextOverhead;
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}
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impl<A, H> KeySizeUser for CtxCommitment<A, H>
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where
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A: AeadCore + KeyInit,
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H: Digest,
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{
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type KeySize = A::KeySize;
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}
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impl<A, H> KeyInit for CtxCommitment<A, H>
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where
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A: AeadCore + KeyInit,
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H: Digest,
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{
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fn new(key: &GenericArray<u8, Self::KeySize>) -> Self {
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Self {
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key: key.clone(),
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naead: A::new(key),
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_digest: PhantomData,
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}
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}
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}
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impl<A, H> CtxCommitment<A, H>
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where
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A: AeadCore + KeyInit + AeadInPlace,
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H: Digest,
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{
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/// Currently not in [`AeadInPlace`] due to the inability to decrypt without verifying
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/// the tag.
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pub fn encrypt_in_place_detached(
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&self,
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nonce: &Nonce<Self>,
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associated_data: &[u8],
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buffer: &mut [u8],
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) -> Result<Tag<Self>, Error> {
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let mut tag = Tag::<Self>::default();
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let ntag = self
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.naead
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.encrypt_in_place_detached(nonce, associated_data, buffer)?;
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H::new()
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.chain_update(&self.key)
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.chain_update(nonce)
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.chain_update(associated_data)
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.chain_update(ntag)
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.finalize_into(&mut tag);
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Ok(tag)
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}
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}
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