Community ALTCHA Rust Library  

Community implementation of the ALTCHA library in Rust for your own server application to create and validate challenges and responses.

For more information about ALTCHA https://altcha.org/docs

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Features

• Compatible with the ALTCHA client-side widget
• Generates and validates self-hosted challenges
• Expiring challenges option
• Supports the algorithms SHA256, SHA384, SHA512, and SHA1 (via optional feature flag)
• With v0.3, enforces delimited salt to prevent replay attacks; see https://altcha.org/security-advisory/

Not part of this library:

• Methods to call ALTCHA's spam filter API
• machine-to-machine ALTCHA
• Store previously verified challenges to prevent replay attacks

Setup

[dependencies]
altcha-lib-rs = { version = "0", features = ["json"] } # with SHA1: ["json", "sha1"]

Example

use altcha_lib_rs::{create_challenge, verify_json_solution, 
                    Payload, Challenge, ChallengeOptions};

fn main() {
    // create a challenge
    let challenge = create_challenge(ChallengeOptions {
        hmac_key: "super-secret",
        expires: Some(Utc::now() + chrono::TimeDelta::minutes(1)),
        ..Default::default()
    }).expect("should be ok");

    // transmit the challenge to the client and let the client solve it
    let res = solve_challenge(&challenge.challenge, &challenge.salt, None, None, 0)
        .expect("need to be solved");
    // pack the solution into a json string
    let payload = Payload {
        algorithm: challenge.algorithm,
        challenge: challenge.challenge,
        number: res,
        salt: challenge.salt,
        signature: challenge.signature,
        took: None,
    };
    let string_payload = serde_json::to_string(&payload).unwrap();

    // receive the solution from the client and verify it
    verify_json_solution(&string_payload, "super-secret", true).expect("should be verified");
}

See example server