Crate secp256k1

Expand description

Secp256k1

Rust bindings for Pieter Wuille’s secp256k1 library, which is used for fast and accurate manipulation of ECDSA signatures on the secp256k1 curve. Such signatures are used extensively by the Bitcoin network and its derivatives.

To minimize dependencies, some functions are feature-gated. To generate random keys or to re-randomize a context object, compile with the “rand” feature. To de/serialize objects with serde, compile with “serde”.

Where possible, the bindings use the Rust type system to ensure that API usage errors are impossible. For example, the library uses context objects that contain precomputation tables which are created on object construction. Since this is a slow operation (10+ milliseconds, vs ~50 microseconds for typical crypto operations, on a 2.70 Ghz i7-6820HQ) the tables are optional, giving a performance boost for users who only care about signing, only care about verification, or only care about parsing. In the upstream library, if you attempt to sign a message using a context that does not support this, it will trigger an assertion failure and terminate the program. In rust-secp256k1, this is caught at compile-time; in fact, it is impossible to compile code that will trigger any assertion failures in the upstream library.

extern crate secp256k1;
extern crate rand;

use rand::OsRng;
use secp256k1::{Secp256k1, Message};

let secp = Secp256k1::new();
let mut rng = OsRng::new().expect("OsRng");
let (secret_key, public_key) = secp.generate_keypair(&mut rng);
let message = Message::from_slice(&[0xab; 32]).expect("32 bytes");

let sig = secp.sign(&message, &secret_key);
assert!(secp.verify(&message, &sig, &public_key).is_ok());

The above code requires rust-secp256k1 to be compiled with the rand feature enabled, to get access to generate_keypair Alternately, keys can be parsed from slices, like

use self::secp256k1::{Secp256k1, Message, SecretKey, PublicKey};

let secp = Secp256k1::new();
let secret_key = SecretKey::from_slice(&secp, &[0xcd; 32]).expect("32 bytes, within curve order");
let public_key = PublicKey::from_secret_key(&secp, &secret_key);
let message = Message::from_slice(&[0xab; 32]).expect("32 bytes");

let sig = secp.sign(&message, &secret_key);
assert!(secp.verify(&message, &sig, &public_key).is_ok());

Users who only want to verify signatures can use a cheaper context, like so:

use secp256k1::{Secp256k1, Message, Signature, PublicKey};

let secp = Secp256k1::verification_only();

let public_key = PublicKey::from_slice(&secp, &[
    0x02,
    0xc6, 0x6e, 0x7d, 0x89, 0x66, 0xb5, 0xc5, 0x55,
    0xaf, 0x58, 0x05, 0x98, 0x9d, 0xa9, 0xfb, 0xf8,
    0xdb, 0x95, 0xe1, 0x56, 0x31, 0xce, 0x35, 0x8c,
    0x3a, 0x17, 0x10, 0xc9, 0x62, 0x67, 0x90, 0x63,
]).expect("public keys must be 33 or 65 bytes, serialized according to SEC 2");

let message = Message::from_slice(&[
    0xaa, 0xdf, 0x7d, 0xe7, 0x82, 0x03, 0x4f, 0xbe,
    0x3d, 0x3d, 0xb2, 0xcb, 0x13, 0xc0, 0xcd, 0x91,
    0xbf, 0x41, 0xcb, 0x08, 0xfa, 0xc7, 0xbd, 0x61,
    0xd5, 0x44, 0x53, 0xcf, 0x6e, 0x82, 0xb4, 0x50,
]).expect("messages must be 32 bytes and are expected to be hashes");

let sig = Signature::from_compact(&secp, &[
    0xdc, 0x4d, 0xc2, 0x64, 0xa9, 0xfe, 0xf1, 0x7a,
    0x3f, 0x25, 0x34, 0x49, 0xcf, 0x8c, 0x39, 0x7a,
    0xb6, 0xf1, 0x6f, 0xb3, 0xd6, 0x3d, 0x86, 0x94,
    0x0b, 0x55, 0x86, 0x82, 0x3d, 0xfd, 0x02, 0xae,
    0x3b, 0x46, 0x1b, 0xb4, 0x33, 0x6b, 0x5e, 0xcb,
    0xae, 0xfd, 0x66, 0x27, 0xaa, 0x92, 0x2e, 0xfc,
    0x04, 0x8f, 0xec, 0x0c, 0x88, 0x1c, 0x10, 0xc4,
    0xc9, 0x42, 0x8f, 0xca, 0x69, 0xc1, 0x32, 0xa2,
]).expect("compact signatures are 64 bytes; DER signatures are 68-72 bytes");

assert!(secp.verify(&message, &sig, &public_key).is_ok());