1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
/*
* Counter mode
* (C) 1999-2011,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ctr.h>
namespace Botan {
CTR_BE::CTR_BE(BlockCipher* ciph) :
m_cipher(ciph),
m_counter(m_cipher->parallel_bytes()),
m_pad(m_counter.size()),
m_iv(m_cipher->block_size()),
m_ctr_size(m_cipher->block_size()),
m_pad_pos(0)
{
}
CTR_BE::CTR_BE(BlockCipher* cipher, size_t ctr_size) :
m_cipher(cipher),
m_counter(m_cipher->parallel_bytes()),
m_pad(m_counter.size()),
m_iv(m_cipher->block_size()),
m_ctr_size(ctr_size),
m_pad_pos(0)
{
//BOTAN_CHECK_ARG(m_ctr_size > 0 && m_ctr_size <= cipher->block_size(), "Invalid CTR size");
if(m_ctr_size == 0 || m_ctr_size > m_cipher->block_size())
throw Invalid_Argument("Invalid CTR-BE counter size");
}
void CTR_BE::clear()
{
m_cipher->clear();
zeroise(m_pad);
zeroise(m_counter);
zeroise(m_iv);
m_pad_pos = 0;
}
void CTR_BE::key_schedule(const uint8_t key[], size_t key_len)
{
m_cipher->set_key(key, key_len);
// Set a default all-zeros IV
set_iv(nullptr, 0);
}
std::string CTR_BE::name() const
{
return ("CTR-BE(" + m_cipher->name() + ")");
}
void CTR_BE::cipher(const uint8_t in[], uint8_t out[], size_t length)
{
while(length >= m_pad.size() - m_pad_pos)
{
xor_buf(out, in, &m_pad[m_pad_pos], m_pad.size() - m_pad_pos);
length -= (m_pad.size() - m_pad_pos);
in += (m_pad.size() - m_pad_pos);
out += (m_pad.size() - m_pad_pos);
increment_counter();
}
xor_buf(out, in, &m_pad[m_pad_pos], length);
m_pad_pos += length;
}
void CTR_BE::set_iv(const uint8_t iv[], size_t iv_len)
{
if(!valid_iv_length(iv_len))
throw Invalid_IV_Length(name(), iv_len);
zeroise(m_iv);
buffer_insert(m_iv, 0, iv, iv_len);
seek(0);
}
/*
* Increment the counter and update the buffer
*/
void CTR_BE::increment_counter()
{
const size_t bs = m_cipher->block_size();
const size_t n_wide = m_counter.size() / bs;
add_counter(n_wide);
m_cipher->encrypt_n(m_counter.data(), m_pad.data(), n_wide);
m_pad_pos = 0;
}
void CTR_BE::add_counter(const uint64_t counter)
{
const size_t bs = m_cipher->block_size();
const size_t n_wide = m_counter.size() / bs;
for(size_t i = 0; i != n_wide; ++i)
{
uint64_t local_counter = counter;
uint16_t carry = static_cast<uint8_t>(local_counter);
for(size_t j = 0; (carry || local_counter) && j != m_ctr_size; ++j)
{
const size_t off = i*bs + (bs-1-j);
const uint16_t cnt = static_cast<uint16_t>(m_counter[off]) + carry;
m_counter[off] = static_cast<uint8_t>(cnt);
local_counter = (local_counter >> 8);
carry = (cnt >> 8) + static_cast<uint8_t>(local_counter);
}
}
}
void CTR_BE::seek(uint64_t offset)
{
const size_t bs = m_cipher->block_size();
const size_t n_wide = m_counter.size() / bs;
const uint64_t base_counter = n_wide * (offset / m_counter.size());
zeroise(m_counter);
buffer_insert(m_counter, 0, m_iv);
// Set m_counter blocks to IV, IV + 1, ... IV + n
for(size_t i = 1; i != n_wide; ++i)
{
buffer_insert(m_counter, i*bs, &m_counter[(i-1)*bs], bs);
for(size_t j = 0; j != m_ctr_size; ++j)
if(++m_counter[i*bs + (bs - 1 - j)])
break;
}
if (base_counter > 0)
add_counter(base_counter);
m_cipher->encrypt_n(m_counter.data(), m_pad.data(), n_wide);
m_pad_pos = offset % m_counter.size();
}
}
|
