137 lines
5.8 KiB
Markdown
137 lines
5.8 KiB
Markdown
[](https://crates.io/crates/double-ratchet-2)
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[](https://github.com/Dione-Software/double-ratchet-2/blob/main/LICENSE)
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[](https://coveralls.io/github/Dione-Software/double-ratchet-2?branch=main)
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[](https://github.com/Dione-Software/double-ratchet-2/actions/workflows/rust.yml)
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# double-ratchet-2
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Implementation of the double ratchet system/encryption as specified by [Signal][1].
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**WARNING! This implementation uses P-256 NOT Curve25519 as specified by Signal!**
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The 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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## Example Usage:
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### Standard:
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```rust
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use double_ratchet_2::ratchet::Ratchet;
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let sk = [1; 32]; // Initial Key created by a symmetric key agreement protocol
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk); // Creating Bobs Ratchet (returns Bobs PublicKey)
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key); // Creating Alice Ratchet with Bobs 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.ratchet_encrypt(&data, ad); // Encrypting message with Alice Ratchet (Alice always needs to send the first message)
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let decrypted = bob_ratchet.ratchet_decrypt(&header, &encrypted, &nonce, ad); // Decrypt message with Bobs Ratchet
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assert_eq!(data, decrypted)
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```
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### With lost message:
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```rust
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let sk = [1; 32]; // Initial Key created by a symmetric key agreement protocol
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let (mut bob_ratchet, public_key) = Ratchet::init_bob(sk); // Creating Bobs Ratchet (returns Bobs PublicKey)
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let mut alice_ratchet = Ratchet::init_alice(sk, public_key); // Creating Alice Ratchet with Bobs 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.ratchet_encrypt(&data, ad); // Lost message
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let (header2, encrypted2, nonce2) = alice_ratchet.ratchet_encrypt(&data, ad); // Successful message
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let decrypted2 = bob_ratchet.ratchet_decrypt(&header2, &encrypted2, &nonce2, ad); // Decrypting second message first
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let decrypted1 = bob_ratchet.ratchet_decrypt(&header1, &encrypted1, &nonce1, ad); // Decrypting latter message
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let comp = decrypted1 == data && decrypted2 == data;
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assert!(comp);
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```
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### Encryption before recieving inital message
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```rust
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use double_ratchet_2::ratchet::Ratchet;
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let sk = [1; 32];
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let ad = b"Associated Data";
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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 (_, _, _) = bob_ratchet.ratchet_encrypt(&data, ad);
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```
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### Encryption after recieving initial message
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However bob can (of course) also encrypt messages. This is possible, after decrypting the first message from alice.
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```rust
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use double_ratchet_2::ratchet::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.ratchet_encrypt(&data, ad);
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let _decrypted1 = bob_ratchet.ratchet_decrypt(&header1, &encrypted1, &nonce1, ad);
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let (header2, encrypted2, nonce2) = bob_ratchet.ratchet_encrypt(&data, ad);
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let decrypted2 = alice_ratchet.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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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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## Example Ratchet with encrypted headers
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```rust
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use double_ratchet_2::ratchet::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.ratchet_encrypt(&data, ad);
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let decrypted = bob_ratchet.ratchet_decrypt(&header, &encrypted, &nonce, ad);
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assert_eq!(data, decrypted)
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```
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## Export / Import Ratchet with encrypted headers
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This ratchet implements import and export functionality. This works over a bincode backend and
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maybe useful for saving Ratchets to and loading from a file.
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```rust
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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);
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assert_eq!(im_ratchet, bob_ratchet)
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```
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## Features
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Currently the crate only supports one feature: ring. If feature is enabled the crate switches
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to ring-compat and uses ring as backend for Sha512 Hashing. May result in slightly better performance.
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TODO:
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- [x] Standard Double Ratchet
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- [x] [Double Ratchet with encrypted headers][3]
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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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Current version: 0.4.0
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License: MIT
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