Expand description
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-std feature. If you are willing to use the rand-std feature, we
have enabled an additional defense-in-depth sidechannel protection for
our context objects, which re-blinds certain operations on secret key
data. To de/serialize objects with serde, compile with “serde”.
Important: serde encoding is not the same as consensus
encoding!
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.
use secp256k1::rand::rngs::OsRng;
use secp256k1::{Secp256k1, Message};
use secp256k1::hashes::sha256;
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_hashed_data::<sha256::Hash>("Hello World!".as_bytes());
let sig = secp.sign_ecdsa(&message, &secret_key);
assert!(secp.verify_ecdsa(&message, &sig, &public_key).is_ok());If the “global-context” feature is enabled you have access to an alternate API.
use secp256k1::rand::thread_rng;
use secp256k1::{generate_keypair, Message};
use secp256k1::hashes::sha256;
let (secret_key, public_key) = generate_keypair(&mut thread_rng());
let message = Message::from_hashed_data::<sha256::Hash>("Hello World!".as_bytes());
let sig = secret_key.sign_ecdsa(&message, &secret_key);
assert!(sig.verify(&message, &public_key).is_ok());The above code requires rust-secp256k1 to be compiled with the rand-std and bitcoin_hashes
feature enabled, to get access to generate_keypair
Alternately, keys and messages can be parsed from slices, like
use secp256k1::{Secp256k1, Message, SecretKey, PublicKey};
let secp = Secp256k1::new();
let secret_key = SecretKey::from_slice(&[0xcd; 32]).expect("32 bytes, within curve order");
let public_key = PublicKey::from_secret_key(&secp, &secret_key);
// This is unsafe unless the supplied byte slice is the output of a cryptographic hash function.
// See the above example for how to use this library together with `bitcoin_hashes`.
let message = Message::from_slice(&[0xab; 32]).expect("32 bytes");
let sig = secp.sign_ecdsa(&message, &secret_key);
assert!(secp.verify_ecdsa(&message, &sig, &public_key).is_ok());Users who only want to verify signatures can use a cheaper context, like so:
use secp256k1::{Secp256k1, Message, ecdsa, PublicKey};
let secp = Secp256k1::verification_only();
let public_key = PublicKey::from_slice(&[
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 = ecdsa::Signature::from_compact(&[
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_ecdsa(&message, &sig, &public_key).is_ok());Observe that the same code using, say signing_only
to generate a context would simply not compile.
Crate features/optional dependencies
This crate provides the following opt-in Cargo features:
std- use standard Rust library, enabled by default.alloc- use theallocstandard Rust library to provide heap allocations.rand- userandlibrary to provide random generator (e.g. to generate keys).rand-std- userandlibrary with itsstdfeature enabled. (Impliesrand.)recovery- enable functions that can compute the public key from signature.lowmemory- optimize the library for low-memory environments.global-context- enable use of global secp256k1 context (impliesstd).serde- implements serialization and deserialization for types in this crate usingserde. Important:serdeencoding is not the same as consensus encoding!bitcoin_hashes- enables interaction with thebitcoin-hashescrate (e.g. conversions).
Re-exports
pub extern crate bitcoin_hashes as hashes;pub extern crate rand;pub extern crate secp256k1_sys;pub extern crate serde;pub use secp256k1_sys as ffi;Modules
Constants related to the API and the underlying curve.
Support for shared secret computations.
Structs and functionality related to the ECDSA signature algorithm.
global-context and stdModule implementing a singleton pattern for a global Secp256k1 context.
schnorrsig
Schnorr Signature related methods.
Serde implementation for the KeyPair type.
Structs
Represents the set of all capabilities with a user preallocated memory.
Error returned when conversion from an integer to Parity fails.
Opaque data structure that holds a keypair consisting of a secret and a public key.
A (hashed) message input to an ECDSA signature.
A Secp256k1 public key, used for verification of signatures.
The secp256k1 engine, used to execute all signature operations.
Secret 256-bit key used as x in an ECDSA signature.
Represents the set of capabilities needed for signing with a user preallocated memory.
Represents the set of capabilities needed for verification with a user preallocated memory.
An x-only public key, used for verification of Schnorr signatures and serialized according to BIP-340.
Enums
std or allocRepresents the set of all capabilities.
An ECDSA error
Represents the parity passed between FFI function calls.
std or allocRepresents the set of capabilities needed for signing.
std or allocRepresents the set of capabilities needed for verification.
Constants
The number 1 encoded as a secret key.
Statics
A global static context to avoid repeatedly creating contexts.
Traits
A trait for all kinds of contexts that lets you define the exact flags and a function to deallocate memory. It isn’t possible to implement this for types outside this crate.
Marker trait for indicating that an instance of Secp256k1 can be used for signing.
Trait describing something that promises to be a 32-byte random number; in particular,
it has negligible probability of being zero or overflowing the group order. Such objects
may be converted to Messages without any error paths.
Marker trait for indicating that an instance of Secp256k1 can be used for verification.
Functions
global-context and randGenerates a random keypair using the global SECP256K1 context.
Type Definitions
backwards compatible re-export of ecdsa signatures