Cast: Added support for AES-CTR crypto.

media/cast/cast_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_CAST_DEFINES_H_
 #define MEDIA_CAST_CAST_DEFINES_H_
 
 #include <map>
 #include <set>
 
@@ skipping 28 matching lines @@
   kDefaultRtpMaxDelayMs = 100,
 };
 
 const uint16 kRtcpCastAllPacketsLost = 0xffff;
 
 const size_t kMinLengthOfRtcp = 8;
 
 // Basic RTP header + cast header.
 const size_t kMinLengthOfRtp = 12 + 6;
 
+const size_t kAesBlockSize = 16;
+
 // 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;
 
 // TODO(pwestin): Re-factor the functions bellow into a class with static
 // methods.
 
 // January 1970, in NTP seconds.
 // Network Time Protocol (NTP), which is in seconds relative to 0h UTC on
@@ skipping 64 matching lines @@
   int64 ntp_time_us = static_cast<int64>(ntp_seconds) *
       base::Time::kMicrosecondsPerSecond +
           static_cast<int64>(ntp_fractions) / kMagicFractionalUnit;
 
   base::TimeDelta elapsed_since_unix_epoch =
       base::TimeDelta::FromMicroseconds(ntp_time_us -
           (kUnixEpochInNtpSeconds * base::Time::kMicrosecondsPerSecond));
   return base::TimeTicks::UnixEpoch() + elapsed_since_unix_epoch;
 }
 
+inline char ConvertFromBase16Char(char base_16) {

[Alpha Left Google, 2013/11/07 01:10:11]

Don't do this. You should assume the key and IV are already binary strings. It
is really the application (test app / chrome) to convert from base64 to binary.
Also there's already base/base64.h that does the conversion.

[pwestin, 2013/11/07 17:16:04]

Moved to test app. I did find the base 64 but not the base 16 in chromium 

+  DCHECK((base_16 >= '0' && base_16 <= '9') ||
+         (base_16 >= 'a' && base_16 <= 'f') ||
+         (base_16 >= 'A' && base_16 <= 'F'));
+
+  if (base_16 >= '0' && base_16 <= '9') {
+    return base_16 - '0';
+  }
+  if (base_16 >= 'a' && base_16 <= 'f') {
+    return base_16 - 'a' + 10;
+  }
+  return base_16 - 'A' + 10;
+}
+
+inline std::string ConvertFromBase16String(std::string base_16) {
+  std::string compressed;
+  DCHECK(base_16.size() % 2 == 0) << "Must be a multiple of 2";
+  compressed.reserve(base_16.size() / 2);
+
+  for (std::string::iterator it = base_16.begin(); it != base_16.end(); ++it) {
+    char first_part = ConvertFromBase16Char(*it++);
+    char second_part = ConvertFromBase16Char(*it);
+    compressed.push_back((first_part << 4) + second_part);
+  }
+  return compressed;
+}
+
+inline std::string GetAesNounce(uint32 frame_id, const std::string& iv_mask) {
+  std::string aes_ivec(kAesBlockSize, 0);
+
+  aes_ivec[11] = frame_id & 0xff;
+  aes_ivec[10] = (frame_id >> 8) & 0xff;
+  aes_ivec[9] = (frame_id >> 16) & 0xff;
+  aes_ivec[8] = (frame_id >> 24) & 0xff;
+
+  for (size_t i = 0; i < kAesBlockSize; ++i) {
+    aes_ivec[i] ^= iv_mask[i];
+  }
+  return aes_ivec;
+}
+
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_CAST_DEFINES_H_