Cast: Adding helper crypto classes

media/cast/transport/cast_transport_defines.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_CAST_TRANSPORT_CAST_TRANSPORT_DEFINES_H_
 #define MEDIA_CAST_TRANSPORT_CAST_TRANSPORT_DEFINES_H_
 
 #include <list>
 #include <map>
 #include <set>
+#include <string>
 
 #include "base/basictypes.h"
 #include "base/time/time.h"
 
 namespace media {
 namespace cast {
 namespace transport {
 
 // TODO(mikhal): Implement and add more types.
 enum CastTransportStatus {
   TRANSPORT_UNINITIALIZED = 0,
   TRANSPORT_INITIALIZED,
   TRANSPORT_INVALID_CRYPTO_CONFIG,
   TRANSPORT_SOCKET_ERROR
 };
 
 const size_t kMaxIpPacketSize = 1500;
 // Each uint16 represents one packet id within a cast frame.
 typedef std::set<uint16> PacketIdSet;
 // Each uint8 represents one cast frame.
 typedef std::map<uint8, PacketIdSet> MissingFramesAndPacketsMap;
 
+// Crypto.
+const size_t kAesBlockSize = 16;
+const size_t kAesKeySize = 16;
+
+inline std::string GetAesNonce(uint32 frame_id, const std::string& iv_mask) {
+  std::string aes_nonce(kAesBlockSize, 0);
+
+  // Serializing frame_id in big-endian order (aes_nonce[8] is the most
+  // significant byte of frame_id).
+  aes_nonce[11] = frame_id & 0xff;
+  aes_nonce[10] = (frame_id >> 8) & 0xff;
+  aes_nonce[9] = (frame_id >> 16) & 0xff;
+  aes_nonce[8] = (frame_id >> 24) & 0xff;
+
+  for (size_t i = 0; i < kAesBlockSize; ++i) {
+    aes_nonce[i] ^= iv_mask[i];
+  }
+  return aes_nonce;
+}
+
 // Rtcp defines.
 
 enum RtcpPacketTypes {
   kPacketTypeLow = 194,  // SMPTE time-code mapping.
   kPacketTypeInterArrivalJitterReport = 195,
   kPacketTypeSenderReport = 200,
   kPacketTypeReceiverReport = 201,
   kPacketTypeSdes = 202,
   kPacketTypeBye = 203,
   kPacketTypeApplicationDefined = 204,
@@ skipping 78 matching lines @@
   base::TimeDelta recorded_delta = time_ticks - zero_time;
   // Timestamp is in 90 KHz for video.
   return static_cast<uint32>(recorded_delta.InMilliseconds() * 90);
 }
 
 }  // namespace transport
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_TRANSPORT_CAST_TRANSPORT_DEFINES_H_