├── go.mod
├── ecdh.go
├── LICENSE
└── ecdh_test.go


/go.mod:
--------------------------------------------------------------------------------
1 | module github.com/fd/ecdh
2 | 


--------------------------------------------------------------------------------
/ecdh.go:
--------------------------------------------------------------------------------
 1 | // Package ecdh implments Elliptic curve Diffie–Hellman key sharing
 2 | package ecdh
 3 | 
 4 | import (
 5 | 	"crypto/elliptic"
 6 | 	"math/big"
 7 | )
 8 | 
 9 | // ComputeShared computes the shared key for the private key material priv and
10 | // the x and y public coordinates
11 | func ComputeShared(curve elliptic.Curve, x, y *big.Int, priv []byte) []byte {
12 | 	x, _ = curve.ScalarMult(x, y, priv)
13 | 	return x.Bytes()
14 | }
15 | 


--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
 1 | The MIT License (MIT)
 2 | 
 3 | Copyright (c) 2015 Simon Menke
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 
23 | 


--------------------------------------------------------------------------------
/ecdh_test.go:
--------------------------------------------------------------------------------
 1 | package ecdh
 2 | 
 3 | import (
 4 | 	"bytes"
 5 | 	"crypto/elliptic"
 6 | 	"crypto/rand"
 7 | 	"testing"
 8 | 
 9 | 	"github.com/fd/secp160r1"
10 | )
11 | 
12 | func Test_ComputeShared_P256(t *testing.T) {
13 | 	curve := elliptic.P256()
14 | 
15 | 	for i := 100; i > 0; i-- {
16 | 		prv1, x1, y1, err := elliptic.GenerateKey(curve, rand.Reader)
17 | 		if err != nil {
18 | 			t.Fatal(err)
19 | 		}
20 | 		if prv1 == nil {
21 | 			t.Fatal("expected prv1 to be non-nil")
22 | 		}
23 | 		if x1 == nil {
24 | 			t.Fatal("expected x1 to be non-nil")
25 | 		}
26 | 		if y1 == nil {
27 | 			t.Fatal("expected y1 to be non-nil")
28 | 		}
29 | 
30 | 		prv2, x2, y2, err := elliptic.GenerateKey(curve, rand.Reader)
31 | 		if err != nil {
32 | 			t.Fatal(err)
33 | 		}
34 | 		if prv2 == nil {
35 | 			t.Fatal("expected prv2 to be non-nil")
36 | 		}
37 | 		if x2 == nil {
38 | 			t.Fatal("expected x2 to be non-nil")
39 | 		}
40 | 		if y2 == nil {
41 | 			t.Fatal("expected y2 to be non-nil")
42 | 		}
43 | 
44 | 		shared1 := ComputeShared(curve, x2, y2, prv1)
45 | 		shared2 := ComputeShared(curve, x1, y1, prv2)
46 | 
47 | 		if !bytes.Equal(shared1, shared2) {
48 | 			t.Fatal("expected shared1 and shared2 to be equal")
49 | 		}
50 | 	}
51 | }
52 | 
53 | func Test_ComputeShared_P160(t *testing.T) {
54 | 	curve := secp160r1.P160()
55 | 
56 | 	for i := 100; i > 0; i-- {
57 | 		prv1, x1, y1, err := elliptic.GenerateKey(curve, rand.Reader)
58 | 		if err != nil {
59 | 			t.Fatal(err)
60 | 		}
61 | 		if prv1 == nil {
62 | 			t.Fatal("expected prv1 to be non-nil")
63 | 		}
64 | 		if x1 == nil {
65 | 			t.Fatal("expected x1 to be non-nil")
66 | 		}
67 | 		if y1 == nil {
68 | 			t.Fatal("expected y1 to be non-nil")
69 | 		}
70 | 
71 | 		prv2, x2, y2, err := elliptic.GenerateKey(curve, rand.Reader)
72 | 		if err != nil {
73 | 			t.Fatal(err)
74 | 		}
75 | 		if prv2 == nil {
76 | 			t.Fatal("expected prv2 to be non-nil")
77 | 		}
78 | 		if x2 == nil {
79 | 			t.Fatal("expected x2 to be non-nil")
80 | 		}
81 | 		if y2 == nil {
82 | 			t.Fatal("expected y2 to be non-nil")
83 | 		}
84 | 
85 | 		shared1 := ComputeShared(curve, x2, y2, prv1)
86 | 		shared2 := ComputeShared(curve, x1, y1, prv2)
87 | 
88 | 		if !bytes.Equal(shared1, shared2) {
89 | 			t.Fatal("expected shared1 and shared2 to be equal")
90 | 		}
91 | 	}
92 | }
93 | 


--------------------------------------------------------------------------------