Double_ratchet

attempted implementation of the double ratcheting algorithm, with DH procedure only happening once in a while, defined by some parameter. The naming of fields and structs are made to comply with the LoRaRatchet protocol, such that it can be integrated into a LoRaWAN context.

Basic usage:

The repository consists of two parties, the ED and the AS>

    use rand_core::OsRng;

    use doubleratchet::r#as::ASRatchet;
    use doubleratchet::ed::EDRatchet;
    let sk = [
        16, 8, 7, 78, 159, 104, 210, 58, 89, 216, 177, 79, 10, 252, 39, 141, 8, 160, 148, 36, 29,
        68, 31, 49, 89, 67, 233, 53, 16, 210, 28, 207,
    ];
    let downlink = [
        0, 171, 247, 26, 19, 92, 119, 193, 156, 216, 49, 89, 90, 174, 165, 23, 124, 247, 30, 79,
        73, 164, 55, 63, 178, 39, 228, 26, 180, 224, 173, 104,
    ];
    let uplink = [
        218, 132, 151, 66, 151, 72, 196, 104, 152, 13, 117, 94, 224, 7, 231, 216, 62, 155, 135, 52,
        59, 100, 217, 236, 115, 100, 161, 95, 8, 146, 123, 146,
    ];

    let devaddr = [1, 2, 3, 2];


    let mut ed_ratchet = EDRatchet::new(sk, downlink, uplink, devaddr, OsRng);

    let mut as_ratchet = ASRatchet::new(sk, uplink, downlink, devaddr, OsRng);

The above code initializes the two parties withtheir shared root key, sending chain key, and receiving chain key. The caller also needs to supply a devvaddr, which is a sort of connection identifier, and some implementation of a rng, that implements RngCore and CryptoRng

Once this is done, both parties can encrypt and decrpyt messages. Receiving messages can be handled by calling the receive functions, which may fail in the case of a decrpytion or deserialization error. It also returns a boolean b indicating whether the returned value should be sent back to the ED.

    let enc0 = ed_ratchet.ratchet_encrypt_payload(b"msg");

    let dec0 = match as_ratchet.receive(enci) {
        Ok((x, _b)) => x,
        Err(s) => panic!("error unpacking {}", s),
    };

The ED can initialize a ratcheting step:

    let dhr_req = ed_ratchet.initiate_ratch();
    let dh_ack = match as_ratchet.receive(dhr_req) {
        Ok((x, _b)) => x,
        Err(s) => panic!("decrypt error {}", s), 
    };

    match ed_ratchet.receive(dh_ack) {
        Ok(_x) => println!("succesfull ratch"),
        Err(s) => panic!("rathcet error {}", s),
    }

THe ED initiates the ratchet, which is received by the AS, who sends back the value it ouputs from it's receive function.