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
|
/*************************************************
* CTR Mode Source File *
* (C) 1999-2005 The Botan Project *
*************************************************/
#include <botan/ctr.h>
#include <botan/lookup.h>
#include <botan/bit_ops.h>
namespace Botan {
/*************************************************
* CTR-BE Constructor *
*************************************************/
CTR_BE::CTR_BE(const std::string& cipher_name) :
BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
{
}
/*************************************************
* CTR-BE Constructor *
*************************************************/
CTR_BE::CTR_BE(const std::string& cipher_name, const SymmetricKey& key,
const InitializationVector& iv) :
BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
{
set_key(key);
set_iv(iv);
}
/*************************************************
* CTR-BE Encryption/Decryption *
*************************************************/
void CTR_BE::write(const byte input[], u32bit length)
{
u32bit copied = std::min(BLOCK_SIZE - position, length);
xor_buf(buffer + position, input, copied);
send(buffer + position, copied);
input += copied;
length -= copied;
position += copied;
if(position == BLOCK_SIZE)
increment_counter();
while(length >= BLOCK_SIZE)
{
xor_buf(buffer, input, BLOCK_SIZE);
send(buffer, BLOCK_SIZE);
input += BLOCK_SIZE;
length -= BLOCK_SIZE;
increment_counter();
}
xor_buf(buffer + position, input, length);
send(buffer + position, length);
position += length;
}
/*************************************************
* Increment the counter and update the buffer *
*************************************************/
void CTR_BE::increment_counter()
{
for(s32bit j = BLOCK_SIZE - 1; j >= 0; j--)
if(++state[j])
break;
cipher->encrypt(state, buffer);
position = 0;
}
}
|
