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. 4 5 #ifndef CRYPTO_HKDF_H_ 6 #define CRYPTO_HKDF_H_ 7 8 #include <vector> 9 10 #include "base/basictypes.h" 11 #include "base/memory/scoped_ptr.h" 12 #include "base/strings/string_piece.h" 13 #include "build/build_config.h" 14 #include "crypto/crypto_export.h" 15 16 namespace crypto { 17 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 { 22 public: 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 27 // 64 bytes. 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 30 // string). 31 // |key_bytes_to_generate|: the number of bytes of key material to generate. 32 // |iv_bytes_to_generate|: the number of bytes of IV to generate. 33 HKDF(const base::StringPiece& secret, 34 const base::StringPiece& salt, 35 const base::StringPiece& info, 36 size_t key_bytes_to_generate, 37 size_t iv_bytes_to_generate); 38 ~HKDF(); 39 client_write_key()40 base::StringPiece client_write_key() const { 41 return client_write_key_; 42 } client_write_iv()43 base::StringPiece client_write_iv() const { 44 return client_write_iv_; 45 } server_write_key()46 base::StringPiece server_write_key() const { 47 return server_write_key_; 48 } server_write_iv()49 base::StringPiece server_write_iv() const { 50 return server_write_iv_; 51 } 52 53 private: 54 std::vector<uint8> output_; 55 56 base::StringPiece client_write_key_; 57 base::StringPiece server_write_key_; 58 base::StringPiece client_write_iv_; 59 base::StringPiece server_write_iv_; 60 }; 61 62 } // namespace crypto 63 64 #endif // CRYPTO_HKDF_H_ 65