181 lines
6 KiB
Markdown
181 lines
6 KiB
Markdown
[](https://crates.io/crates/double-ratchet-rs)
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[](https://github.com/notsatvrn/double-ratchet-rs/blob/main/LICENSE)
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[](https://coveralls.io/github/notsatvrn/double-ratchet-rs?branch=main)
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[](https://github.com/notsatvrn/double-ratchet-rs/actions/workflows/rust.yml)
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# double-ratchet-rs
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A pure Rust implementation of the Double Ratchet algorithm as described by [Signal][1].
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This implementation follows the cryptographic recommendations provided by [Signal][2].
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The AEAD algorithm uses a constant Nonce. This might be changed in the future.
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Fork of [double-ratchet-2](https://github.com/Dione-Software/double-ratchet-2).
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## Examples
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### Standard Usage
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Alice encrypts a message which is then decrypted by Bob.
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```rust
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use double_ratchet_rs::Ratchet;
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let sk = [1; 32]; // Shared key created by a symmetric key agreement protocol
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk); // Creating Bob's Ratchet (returns Bob's PublicKey)
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key); // Creating Alice's Ratchet with Bob's PublicKey
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let data = b"Hello World".to_vec(); // Data to be encrypted
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let ad = b"Associated Data"; // Associated data
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let (header, encrypted, nonce) = alice_ratchet.encrypt(&data, ad); // Encrypting message with Alice's Ratchet (Alice always needs to send the first message)
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let decrypted = bob_ratchet.decrypt(&header, &encrypted, &nonce, ad); // Decrypt message with Bob's Ratchet
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assert_eq!(data, decrypted)
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```
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### Recovering a Lost Message
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Alice encrypts 2 messages for Bob.
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The latest message must be decrypted first.
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```rust
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use double_ratchet_rs::Ratchet;
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let sk = [1; 32]; // Shared key created by a symmetric key agreement protocol
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk); // Creating Bob's Ratchet (returns Bob's PublicKey)
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key); // Creating Alice's Ratchet with Bob's PublicKey
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let data = b"Hello World".to_vec(); // Data to be encrypted
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let ad = b"Associated Data"; // Associated data
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let (header1, encrypted1, nonce1) = alice_ratchet.encrypt(&data, ad); // Lost message
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let (header2, encrypted2, nonce2) = alice_ratchet.encrypt(&data, ad); // Successful message
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let decrypted2 = bob_ratchet.decrypt(&header2, &encrypted2, &nonce2, ad); // Decrypting second message first
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let decrypted1 = bob_ratchet.decrypt(&header1, &encrypted1, &nonce1, ad); // Decrypting latter message
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assert_eq!(data, decrypted1);
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assert_eq!(data, decrypted2);
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```
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### Encryption Before Decrypting First Message
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Bob encrypts a message before decrypting one from Alice.
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This will result in a panic.
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```rust
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use double_ratchet_rs::Ratchet;
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let sk = [1; 32];
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let (mut bob_ratchet, _) = Ratchet::init_bob(sk);
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let data = b"Hello World".to_vec();
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let ad = b"Associated Data";
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let (_, _, _) = bob_ratchet.encrypt(&data, ad);
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```
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### Encryption After Decrypting First Message
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Bob *can* also encrypt messages.
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This is only possible after decrypting one from Alice first though.
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```rust
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use double_ratchet_rs::Ratchet;
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let sk = [1; 32];
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk);
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key);
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let data = b"Hello World".to_vec();
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let ad = b"Associated Data";
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let (header1, encrypted1, nonce1) = alice_ratchet.encrypt(&data, ad);
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let _decrypted1 = bob_ratchet.decrypt(&header1, &encrypted1, &nonce1, ad);
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let (header2, encrypted2, nonce2) = bob_ratchet.encrypt(&data, ad);
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let decrypted2 = alice_ratchet.decrypt(&header2, &encrypted2, &nonce2, ad);
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assert_eq!(data, decrypted2);
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```
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### Constructing and Deconstructing Headers
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```rust
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use double_ratchet_rs::{Header, Ratchet};
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let sk = [1; 32];
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk);
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key);
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let data = b"hello World".to_vec();
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let ad = b"Associated Data";
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let (header, _, _) = alice_ratchet.encrypt(&data, ad);
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let header_bytes: Vec<u8> = header.clone().into();
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let header_const = Header::from(header_bytes);
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assert_eq!(header, header_const);
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```
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### Encrypted Headers
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```rust
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use double_ratchet_rs::RatchetEncHeader;
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let sk = [0; 32];
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let shared_hka = [1; 32];
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let shared_nhkb = [2; 32];
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let (mut bob_ratchet, public_key) = RatchetEncHeader::init_bob(sk, shared_hka, shared_nhkb);
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let mut alice_ratchet = RatchetEncHeader::init_alice(sk, public_key, shared_hka, shared_nhkb);
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let data = b"Hello World".to_vec();
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let ad = b"Associated Data";
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let (header, encrypted, nonce) = alice_ratchet.encrypt(&data, ad);
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let decrypted = bob_ratchet.decrypt(&header, &encrypted, &nonce, ad);
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assert_eq!(data, decrypted)
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```
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### Exporting / Importing Ratchet w/ Encrypted Headers
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This can be used for storing and using ratchets in a file.
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```rust
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use double_ratchet_rs::RatchetEncHeader;
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let sk = [0; 32];
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let shared_hka = [1; 32];
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let shared_nhkb = [2; 32];
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let (bob_ratchet, public_key) = RatchetEncHeader::init_bob(sk, shared_hka, shared_nhkb);
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let ex_ratchet = bob_ratchet.export();
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let im_ratchet = RatchetEncHeader::import(&ex_ratchet).unwrap();
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assert_eq!(im_ratchet, bob_ratchet)
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```
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## Features
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- `hashbrown`: Use `hashbrown` for `HashMap`. Enabled by default for `no_std` support.
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- `std`: Use `std` instead of `alloc`. Can be used with `hashbrown`, but it isn't required.
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## **M**inimum **S**upported **R**ust **V**ersion (MSRV)
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The current MSRV is 1.60.0 without `hashbrown` and 1.64.0 with `hashbrown`.
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## License
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This project is licensed under the [MIT license](https://github.com/notsatvrn/double-ratchet-rs/blob/main/LICENSE).
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[1]: https://signal.org/docs/specifications/doubleratchet/
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[2]: https://signal.org/docs/specifications/doubleratchet/#recommended-cryptographic-algorithms
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[3]: https://signal.org/docs/specifications/doubleratchet/#double-ratchet-with-header-encryption
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