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// 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.
// +build ignore
package hkdf_test
import (
"bytes"
"crypto/rand"
"crypto/sha256"
"fmt"
"io"
"internal/x/crypto/hkdf"
)
// Usage example that expands one master secret into three other
// cryptographically secure keys.
func Example_usage() {
// Underlying hash function for HMAC.
hash := sha256.New
// Cryptographically secure master secret.
secret := []byte{0x00, 0x01, 0x02, 0x03} // i.e. NOT this.
// Non-secret salt, optional (can be nil).
// Recommended: hash-length random value.
salt := make([]byte, hash().Size())
if _, err := rand.Read(salt); err != nil {
panic(err)
}
// Non-secret context info, optional (can be nil).
info := []byte("hkdf example")
// Generate three 128-bit derived keys.
hkdf := hkdf.New(hash, secret, salt, info)
var keys [][]byte
for i := 0; i < 3; i++ {
key := make([]byte, 16)
if _, err := io.ReadFull(hkdf, key); err != nil {
panic(err)
}
keys = append(keys, key)
}
for i := range keys {
fmt.Printf("Key #%d: %v\n", i+1, !bytes.Equal(keys[i], make([]byte, 16)))
}
// Output:
// Key #1: true
// Key #2: true
// Key #3: true
}
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