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use asn1_der::{FromDerObject, DerObject};
use lazy_static::lazy_static;
use sha2::{Digest as ShaDigestTrait, Sha256};
use secp256k1 as secp;
use secp::{Message, Signature};
use super::error::DecodingError;
use zeroize::Zeroize;
lazy_static! {
static ref SECP: secp::Secp256k1<secp::All> = secp::Secp256k1::new();
}
#[derive(Clone)]
pub struct Keypair {
secret: SecretKey,
public: PublicKey
}
impl Keypair {
pub fn generate() -> Keypair {
Keypair::from(SecretKey::generate())
}
pub fn public(&self) -> &PublicKey {
&self.public
}
pub fn secret(&self) -> &SecretKey {
&self.secret
}
}
impl From<SecretKey> for Keypair {
fn from(secret: SecretKey) -> Keypair {
let public = PublicKey(secp::key::PublicKey::from_secret_key(&SECP, &secret.0));
Keypair { secret, public }
}
}
impl From<Keypair> for SecretKey {
fn from(kp: Keypair) -> SecretKey {
kp.secret
}
}
#[derive(Clone)]
pub struct SecretKey(secp::key::SecretKey);
impl AsRef<[u8]> for SecretKey {
fn as_ref(&self) -> &[u8] {
&self.0[..]
}
}
impl SecretKey {
pub fn generate() -> SecretKey {
SecretKey(secp::key::SecretKey::new(&mut secp::rand::thread_rng()))
}
pub fn from_bytes(mut sk: impl AsMut<[u8]>) -> Result<SecretKey, DecodingError> {
let sk_bytes = sk.as_mut();
let secret = secp::key::SecretKey::from_slice(&*sk_bytes)
.map_err(|e| DecodingError::new("Secp256k1 secret key", e))?;
sk_bytes.zeroize();
Ok(SecretKey(secret))
}
pub fn from_der(mut der: impl AsMut<[u8]>) -> Result<SecretKey, DecodingError> {
let der_obj = der.as_mut();
let obj: Vec<DerObject> = FromDerObject::deserialize((&*der_obj).iter())
.map_err(|e| DecodingError::new("Secp256k1 DER ECPrivateKey", e))?;
der_obj.zeroize();
let sk_obj = obj.into_iter().nth(1)
.ok_or_else(|| "Not enough elements in DER".to_string())?;
let mut sk_bytes: Vec<u8> = FromDerObject::from_der_object(sk_obj)
.map_err(|e| e.to_string())?;
let sk = SecretKey::from_bytes(&mut sk_bytes)?;
sk_bytes.zeroize();
Ok(sk)
}
pub fn sign(&self, msg: &[u8]) -> Vec<u8> {
let m = Message::from_slice(Sha256::digest(&msg).as_ref())
.expect("digest output length doesn't match secp256k1 input length");
SECP.sign(&m, &self.0).serialize_der()
}
}
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct PublicKey(secp::key::PublicKey);
impl PublicKey {
pub fn verify(&self, msg: &[u8], sig: &[u8]) -> bool {
Message::from_slice(&Sha256::digest(msg))
.and_then(|m| Signature::from_der(sig)
.and_then(|s| SECP.verify(&m, &s, &self.0))).is_ok()
}
pub fn encode(&self) -> [u8; 33] {
self.0.serialize()
}
pub fn decode(k: &[u8]) -> Result<PublicKey, DecodingError> {
secp256k1::PublicKey::from_slice(k)
.map_err(|e| DecodingError::new("Secp256k1 public key", e))
.map(PublicKey)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn secp256k1_secret_from_bytes() {
let sk1 = SecretKey::generate();
let mut sk_bytes = [0; 32];
sk_bytes.copy_from_slice(sk1.as_ref());
let sk2 = SecretKey::from_bytes(&mut sk_bytes).unwrap();
assert_eq!(sk1.as_ref(), sk2.as_ref());
assert_eq!(sk_bytes, [0; 32]);
}
}