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
|
// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package hkdf_test
import (
"bytes"
"crypto/rand"
"crypto/sha256"
"fmt"
"golang.org/x/crypto/hkdf"
"io"
)
// Usage example that expands one master key into three other cryptographically
// secure keys.
func Example_usage() {
// Underlying hash function to use
hash := sha256.New
// Cryptographically secure master key.
master := []byte{0x00, 0x01, 0x02, 0x03} // i.e. NOT this.
// Non secret salt, optional (can be nil)
// Recommended: hash-length sized random
salt := make([]byte, hash().Size())
n, err := io.ReadFull(rand.Reader, salt)
if n != len(salt) || err != nil {
fmt.Println("error:", err)
return
}
// Non secret context specific info, optional (can be nil).
// Note, independent from the master key.
info := []byte{0x03, 0x14, 0x15, 0x92, 0x65}
// Create the key derivation function
hkdf := hkdf.New(hash, master, salt, info)
// Generate the required keys
keys := make([][]byte, 3)
for i := 0; i < len(keys); i++ {
keys[i] = make([]byte, 24)
n, err := io.ReadFull(hkdf, keys[i])
if n != len(keys[i]) || err != nil {
fmt.Println("error:", err)
return
}
}
// Keys should contain 192 bit random keys
for i := 1; i <= len(keys); i++ {
fmt.Printf("Key #%d: %v\n", i, !bytes.Equal(keys[i-1], make([]byte, 24)))
}
// Output:
// Key #1: true
// Key #2: true
// Key #3: true
}
|
