57 lines
1.2 KiB
Go
57 lines
1.2 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package hkdf_test
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import (
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"bytes"
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"crypto/rand"
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"crypto/sha256"
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"fmt"
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"io"
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"golang.org/x/crypto/hkdf"
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)
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// Usage example that expands one master secret into three other
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// cryptographically secure keys.
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func Example_usage() {
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// Underlying hash function for HMAC.
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hash := sha256.New
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// Cryptographically secure master secret.
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secret := []byte{0x00, 0x01, 0x02, 0x03} // i.e. NOT this.
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// Non-secret salt, optional (can be nil).
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// Recommended: hash-length random value.
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salt := make([]byte, hash().Size())
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if _, err := rand.Read(salt); err != nil {
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panic(err)
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}
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// Non-secret context info, optional (can be nil).
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info := []byte("hkdf example")
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// Generate three 128-bit derived keys.
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hkdf := hkdf.New(hash, secret, salt, info)
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var keys [][]byte
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for i := 0; i < 3; i++ {
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key := make([]byte, 16)
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if _, err := io.ReadFull(hkdf, key); err != nil {
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panic(err)
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}
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keys = append(keys, key)
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}
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for i := range keys {
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fmt.Printf("Key #%d: %v\n", i+1, !bytes.Equal(keys[i], make([]byte, 16)))
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}
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// Output:
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// Key #1: true
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// Key #2: true
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// Key #3: true
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}
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