1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
13 #include "base/strings/string_piece.h"
14 #include "crypto/crypto_export.h"
18 // HKDF implements the key derivation function specified in RFC 5869 (using
19 // SHA-256) and outputs key material, as needed by QUIC.
20 // See https://tools.ietf.org/html/rfc5869 for details.
21 class CRYPTO_EXPORT HKDF {
23 // |secret|: the input shared secret (or, from RFC 5869, the IKM).
24 // |salt|: an (optional) public salt / non-secret random value. While
25 // optional, callers are strongly recommended to provide a salt. There is no
26 // added security value in making this larger than the SHA-256 block size of
28 // |info|: an (optional) label to distinguish different uses of HKDF. It is
29 // optional context and application specific information (can be a zero-length
31 // |key_bytes_to_generate|: the number of bytes of key material to generate
32 // for both client and server.
33 // |iv_bytes_to_generate|: the number of bytes of IV to generate for both
35 // |subkey_secret_bytes_to_generate|: the number of bytes of subkey secret to
36 // generate, shared between client and server.
37 HKDF(base::StringPiece secret,
38 base::StringPiece salt,
39 base::StringPiece info,
40 size_t key_bytes_to_generate,
41 size_t iv_bytes_to_generate,
42 size_t subkey_secret_bytes_to_generate);
44 // An alternative constructor that allows the client and server key/IV
45 // lengths to be different.
46 HKDF(base::StringPiece secret,
47 base::StringPiece salt,
48 base::StringPiece info,
49 size_t client_key_bytes_to_generate,
50 size_t server_key_bytes_to_generate,
51 size_t client_iv_bytes_to_generate,
52 size_t server_iv_bytes_to_generate,
53 size_t subkey_secret_bytes_to_generate);
56 base::StringPiece client_write_key() const {
57 return client_write_key_;
59 base::StringPiece client_write_iv() const {
60 return client_write_iv_;
62 base::StringPiece server_write_key() const {
63 return server_write_key_;
65 base::StringPiece server_write_iv() const {
66 return server_write_iv_;
68 base::StringPiece subkey_secret() const {
69 return subkey_secret_;
73 std::vector<uint8_t> output_;
75 base::StringPiece client_write_key_;
76 base::StringPiece server_write_key_;
77 base::StringPiece client_write_iv_;
78 base::StringPiece server_write_iv_;
79 base::StringPiece subkey_secret_;
84 #endif // CRYPTO_HKDF_H_