secp256k1 0.6.0

Rust bindings for Pieter Wuille's `libsecp256k1` library. Implements ECDSA for the SECG elliptic curve group secp256k1 and related utilities.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

// Bitcoin secp256k1 bindings
// Written in 2015 by
//   Andrew Poelstra
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! # ECDH
//! Support for shared secret computations
//!

use std::ops;

use super::Secp256k1;
use key::{SecretKey, PublicKey};
use ffi;

/// A tag used for recovering the public key from a compact signature
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct SharedSecret(ffi::SharedSecret);

impl SharedSecret {
    /// Creates a new shared secret from a pubkey and secret key
    #[inline]
    pub fn new(secp: &Secp256k1, point: &PublicKey, scalar: &SecretKey) -> SharedSecret {
        unsafe {
            let mut ss = ffi::SharedSecret::blank();
            let res = ffi::secp256k1_ecdh(secp.ctx, &mut ss, point.as_ptr(), scalar.as_ptr());
            debug_assert_eq!(res, 1);
            SharedSecret(ss)
        }
    }

    /// Obtains a raw pointer suitable for use with FFI functions
    #[inline]
    pub fn as_ptr(&self) -> *const ffi::SharedSecret {
        &self.0 as *const _
    }
}

/// Creates a new shared secret from a FFI shared secret
impl From<ffi::SharedSecret> for SharedSecret {
    #[inline]
    fn from(ss: ffi::SharedSecret) -> SharedSecret {
        SharedSecret(ss)
    }
}


impl ops::Index<usize> for SharedSecret {
    type Output = u8;

    #[inline]
    fn index(&self, index: usize) -> &u8 {
        &self.0[index]
    }
}

impl ops::Index<ops::Range<usize>> for SharedSecret {
    type Output = [u8];

    #[inline]
    fn index(&self, index: ops::Range<usize>) -> &[u8] {
        &self.0[index]
    }
}

impl ops::Index<ops::RangeFrom<usize>> for SharedSecret {
    type Output = [u8];

    #[inline]
    fn index(&self, index: ops::RangeFrom<usize>) -> &[u8] {
        &self.0[index.start..]
    }
}

impl ops::Index<ops::RangeFull> for SharedSecret {
    type Output = [u8];

    #[inline]
    fn index(&self, _: ops::RangeFull) -> &[u8] {
        &self.0[..]
    }
}

#[cfg(test)]
mod tests {
    use rand::thread_rng;
    use super::SharedSecret;
    use super::super::Secp256k1;

    #[test]
    fn ecdh() {
        let s = Secp256k1::with_caps(::ContextFlag::SignOnly);
        let (sk1, pk1) = s.generate_keypair(&mut thread_rng()).unwrap();
        let (sk2, pk2) = s.generate_keypair(&mut thread_rng()).unwrap();

        let sec1 = SharedSecret::new(&s, &pk1, &sk2);
        let sec2 = SharedSecret::new(&s, &pk2, &sk1);
        let sec_odd = SharedSecret::new(&s, &pk1, &sk1);
        assert_eq!(sec1, sec2);
        assert!(sec_odd != sec2);
    }
}

#[cfg(all(test, feature = "unstable"))]
mod benches {
    use rand::thread_rng;
    use test::{Bencher, black_box};

    use super::SharedSecret;
    use super::super::Secp256k1;

    #[bench]
    pub fn bench_ecdh(bh: &mut Bencher) {
        let s = Secp256k1::with_caps(::ContextFlag::SignOnly);
        let (sk, pk) = s.generate_keypair(&mut thread_rng()).unwrap();

        let s = Secp256k1::new();
        bh.iter( || {
            let res = SharedSecret::new(&s, &pk, &sk);
            black_box(res);
        });
    }
}