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/strings/string_piece.h"
  12 #include "crypto/crypto_export.h"
  13
  14 namespace crypto {
  15
  16 // HKDF implements the key derivation function specified in RFC 5869 (using
  17 // SHA-256) and outputs key material, as needed by QUIC.
  18 // See https://tools.ietf.org/html/rfc5869 for details.
  19 class CRYPTO_EXPORT HKDF {
  20  public:
  21   // |secret|: the input shared secret (or, from RFC 5869, the IKM).
  22   // |salt|: an (optional) public salt / non-secret random value. While
  23   // optional, callers are strongly recommended to provide a salt. There is no
  24   // added security value in making this larger than the SHA-256 block size of
  25   // 64 bytes.
  26   // |info|: an (optional) label to distinguish different uses of HKDF. It is
  27   // optional context and application specific information (can be a zero-length
  28   // string).
  29   // |key_bytes_to_generate|: the number of bytes of key material to generate
  30   // for both client and server.
  31   // |iv_bytes_to_generate|: the number of bytes of IV to generate for both
  32   // client and server.
  33   // |subkey_secret_bytes_to_generate|: the number of bytes of subkey secret to
  34   // generate, shared between client and server.
  35   HKDF(const base::StringPiece& secret,
  36        const base::StringPiece& salt,
  37        const base::StringPiece& info,
  38        size_t key_bytes_to_generate,
  39        size_t iv_bytes_to_generate,
  40        size_t subkey_secret_bytes_to_generate);
  41   ~HKDF();
  42
  43   base::StringPiece client_write_key() const {
  44     return client_write_key_;
  45   }
  46   base::StringPiece client_write_iv() const {
  47     return client_write_iv_;
  48   }
  49   base::StringPiece server_write_key() const {
  50     return server_write_key_;
  51   }
  52   base::StringPiece server_write_iv() const {
  53     return server_write_iv_;
  54   }
  55   base::StringPiece subkey_secret() const {
  56     return subkey_secret_;
  57   }
  58
  59  private:
  60   std::vector<uint8> output_;
  61
  62   base::StringPiece client_write_key_;
  63   base::StringPiece server_write_key_;
  64   base::StringPiece client_write_iv_;
  65   base::StringPiece server_write_iv_;
  66   base::StringPiece subkey_secret_;
  67 };
  68
  69 }  // namespace crypto
  70
  71 #endif  // CRYPTO_HKDF_H_