1 /*
2 * ChaCha20
3 * (C) 2014,2018 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #ifndef BOTAN_CHACHA_H_
9 #define BOTAN_CHACHA_H_
10 
11 #include <botan/stream_cipher.h>
12 
13 BOTAN_FUTURE_INTERNAL_HEADER(chacha.h)
14 
15 namespace Botan {
16 
17 /**
18 * DJB's ChaCha (https://cr.yp.to/chacha.html)
19 */
20 class BOTAN_PUBLIC_API(2,0) ChaCha final : public StreamCipher
21    {
22    public:
23       /**
24       * @param rounds number of rounds
25       * @note Currently only 8, 12 or 20 rounds are supported, all others
26       * will throw an exception
27       */
28       explicit ChaCha(size_t rounds = 20);
29 
30       std::string provider() const override;
31 
32       void cipher(const uint8_t in[], uint8_t out[], size_t length) override;
33 
34       void write_keystream(uint8_t out[], size_t len) override;
35 
36       void set_iv(const uint8_t iv[], size_t iv_len) override;
37 
38       /*
39       * ChaCha accepts 0, 8, 12 or 24 byte IVs.
40       * The default IV is a 8 zero bytes.
41       * An IV of length 0 is treated the same as the default zero IV.
42       * An IV of length 24 selects XChaCha mode
43       */
44       bool valid_iv_length(size_t iv_len) const override;
45 
46       size_t default_iv_length() const override;
47 
48       Key_Length_Specification key_spec() const override;
49 
50       void clear() override;
51 
52       StreamCipher* clone() const override;
53 
54       std::string name() const override;
55 
56       void seek(uint64_t offset) override;
57 
58    private:
59       void key_schedule(const uint8_t key[], size_t key_len) override;
60 
61       void initialize_state();
62 
63       void chacha_x8(uint8_t output[64*8], uint32_t state[16], size_t rounds);
64 
65 #if defined(BOTAN_HAS_CHACHA_SIMD32)
66       void chacha_simd32_x4(uint8_t output[64*4], uint32_t state[16], size_t rounds);
67 #endif
68 
69 #if defined(BOTAN_HAS_CHACHA_AVX2)
70       void chacha_avx2_x8(uint8_t output[64*8], uint32_t state[16], size_t rounds);
71 #endif
72 
73       size_t m_rounds;
74       secure_vector<uint32_t> m_key;
75       secure_vector<uint32_t> m_state;
76       secure_vector<uint8_t> m_buffer;
77       size_t m_position = 0;
78    };
79 
80 }
81 
82 #endif
83