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1 // Copyright 2015 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 MEDIA_BASE_ENCRYPTION_SCHEME_H_ | |
6 #define MEDIA_BASE_ENCRYPTION_SCHEME_H_ | |
7 | |
8 #include <stdint.h> | |
9 | |
10 #include "media/base/media_export.h" | |
11 | |
12 namespace media { | |
13 | |
14 // Specification of whether and how the stream is encrypted (in whole or part). | |
15 class MEDIA_EXPORT EncryptionScheme { | |
16 public: | |
17 // Algorithm and mode used for encryption. CIPHER_MODE_UNENCRYPTED indicates | |
18 // no encryption. | |
19 enum CipherMode { | |
20 CIPHER_MODE_UNENCRYPTED, | |
21 CIPHER_MODE_AES_CTR, | |
22 CIPHER_MODE_AES_CBC, | |
23 CIPHER_MODE_MAX = CIPHER_MODE_AES_CBC | |
24 }; | |
25 | |
26 // CENC 3rd Edition adds pattern encryption, through two new protection | |
27 // schemes: 'cens' (with AES-CTR) and 'cbcs' (with AES-CBC). | |
28 // The pattern applies independently to each 'encrypted' part of the frame (as | |
29 // defined by the relevant subsample entries), and reduces further the | |
30 // actual encryption applied through a repeating pattern of (encrypt:skip) | |
31 // 16 byte blocks. For example, in a (1:9) pattern, the first block is | |
32 // encrypted, and the next nine are skipped. This pattern is applied | |
33 // repeatedly until the end of the last 16-byte block in the subsample. | |
34 // Any remaining bytes are left clear. | |
35 // If either of encrypt_blocks or skip_blocks is 0, pattern encryption is | |
36 // disabled. | |
37 class Pattern { | |
38 public: | |
39 Pattern(); | |
40 Pattern(uint32_t encrypt_blocks, uint32_t skip_blocks); | |
41 ~Pattern(); | |
42 | |
43 bool Matches(const Pattern& other) const; | |
44 | |
45 uint32_t encrypt_blocks() const { return encrypt_blocks_; } | |
46 uint32_t skip_blocks() const { return skip_blocks_; } | |
47 | |
48 bool IsInEffect() const; | |
49 | |
50 private: | |
51 uint32_t encrypt_blocks_ = 0; | |
52 uint32_t skip_blocks_ = 0; | |
53 | |
54 // Allow copy and assignment. | |
55 }; | |
56 | |
57 // The default constructor makes an instance that indicates no encryption. | |
58 EncryptionScheme(); | |
59 | |
60 // This constructor allows specification of the cipher mode and the pattern. | |
61 EncryptionScheme(CipherMode mode, const Pattern& pattern); | |
62 ~EncryptionScheme(); | |
63 | |
64 bool Matches(const EncryptionScheme& other) const; | |
65 | |
66 bool is_encrypted() const { return mode_ != CIPHER_MODE_UNENCRYPTED; } | |
67 CipherMode mode() const { return mode_; } | |
68 const Pattern& pattern() const { return pattern_; } | |
69 | |
70 private: | |
71 CipherMode mode_ = CIPHER_MODE_UNENCRYPTED; | |
72 Pattern pattern_; | |
73 | |
74 // Allow copy and assignment. | |
75 }; | |
76 | |
77 } // namespace media | |
78 | |
79 #endif // MEDIA_BASE_ENCRYPTION_SCHEME_H_ | |
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