crypto/hkdf.h

   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
  40   base::StringPiece client_write_key() const {
  41     return client_write_key_;
  42   }
  43   base::StringPiece client_write_iv() const {
  44     return client_write_iv_;
  45   }
  46   base::StringPiece server_write_key() const {
  47     return server_write_key_;
  48   }
  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_