61 lines
1.5 KiB
Go
61 lines
1.5 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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"golang.org/x/crypto/hkdf"
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"io"
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)
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// Usage example that expands one master key into three other cryptographically
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// secure keys.
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func Example_usage() {
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// Underlying hash function to use
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hash := sha256.New
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// Cryptographically secure master key.
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master := []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 sized random
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salt := make([]byte, hash().Size())
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n, err := io.ReadFull(rand.Reader, salt)
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if n != len(salt) || err != nil {
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fmt.Println("error:", err)
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return
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}
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// Non secret context specific info, optional (can be nil).
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// Note, independent from the master key.
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info := []byte{0x03, 0x14, 0x15, 0x92, 0x65}
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// Create the key derivation function
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hkdf := hkdf.New(hash, master, salt, info)
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// Generate the required keys
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keys := make([][]byte, 3)
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for i := 0; i < len(keys); i++ {
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keys[i] = make([]byte, 24)
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n, err := io.ReadFull(hkdf, keys[i])
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if n != len(keys[i]) || err != nil {
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fmt.Println("error:", err)
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return
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}
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}
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// Keys should contain 192 bit random keys
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for i := 1; i <= len(keys); i++ {
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fmt.Printf("Key #%d: %v\n", i, !bytes.Equal(keys[i-1], make([]byte, 24)))
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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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