Unmaintained -- please use this fork instead https://github.com/WesleyBatista/rust-otp
rust-otp is a Rust library for performing the HMAC-based One-time Passsword Algorithm as per RFC 4226 and the Time-based One-time Password Algorithm as per RFC 6238. These are also the algorithms many mobile-based 2FA apps, such as Google Authenticator and Authy, use to generate 2FA codes.
Just add the library as a dependency by adding the following section to your
Cargo.toml file.
[dependencies.otp]
git = "https://github.com/TimDumol/rust-otp"   // first argument is the secret, second argument is the counter
    println!("HOTP: {:?}", otp::make_hotp("base32secret3232".to_ascii_uppercase().as_str(), 0).unwrap());
    assert_eq!(otp::make_hotp(&"base32secret3232".to_ascii_uppercase(), 0).unwrap(), 260182);
    // first argument is the secret, followed by the time step in seconds (Google
    // Authenticator uses a time step of 30), and then the skew in seconds
    // (often used when calculating HOTPs for a sequence of consecutive
    // time intervals, to deal with potential latency and desynchronization).
    println!("TOTP: {:?}", otp::make_totp(&("base32secret3232".to_ascii_uppercase()), 30, 0).unwrap());
    // there is a non-zero possibility of this assertion failing
    assert_ne!(otp::make_totp(&"base32secret3232".to_ascii_uppercase(), 30, 0).unwrap(), 260182_u32);rust-otp is licensed under the MIT license.
The full license is included in this repository in LICENSE.md.