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
|
/*
* Rivest's Package Tranform
*
* (C) 2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/package.h>
#include <botan/filters.h>
#include <botan/ctr.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
namespace AllOrNothingTransform {
void package(RandomNumberGenerator& rng,
BlockCipher* cipher,
const byte input[], u32bit input_len,
byte output[])
{
if(!cipher->valid_keylength(cipher->BLOCK_SIZE))
throw Invalid_Argument("AONT::package: Invalid cipher");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(cipher->BLOCK_SIZE*2, '0');
SymmetricKey package_key(rng, cipher->BLOCK_SIZE);
Pipe pipe(new StreamCipher_Filter(new CTR_BE(cipher), package_key));
pipe.process_msg(input, input_len);
pipe.read(output, pipe.remaining());
// Set K0 (the all zero key)
cipher->set_key(SymmetricKey(all_zeros));
SecureVector<byte> buf(cipher->BLOCK_SIZE);
const u32bit blocks =
(input_len + cipher->BLOCK_SIZE - 1) / cipher->BLOCK_SIZE;
byte* final_block = output + input_len;
clear_mem(final_block, cipher->BLOCK_SIZE);
// XOR the hash blocks into the final block
for(u32bit i = 0; i != blocks; ++i)
{
u32bit left = std::min<u32bit>(cipher->BLOCK_SIZE,
input_len - cipher->BLOCK_SIZE * i);
buf.clear();
copy_mem(&buf[0], output + cipher->BLOCK_SIZE * i, left);
for(u32bit j = 0; j != 4; ++j)
buf[cipher->BLOCK_SIZE - 1 - j] ^= get_byte(3-j, i);
cipher->encrypt(buf);
xor_buf(final_block, buf, cipher->BLOCK_SIZE);
}
// XOR the random package key into the final block
xor_buf(final_block, package_key.begin(), cipher->BLOCK_SIZE);
}
void unpackage(BlockCipher* cipher,
const byte input[], u32bit input_len,
byte output[])
{
if(!cipher->valid_keylength(cipher->BLOCK_SIZE))
throw Invalid_Argument("AONT::unpackage: Invalid cipher");
if(input_len < cipher->BLOCK_SIZE)
throw Invalid_Argument("AONT::unpackage: Input too short");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(cipher->BLOCK_SIZE*2, '0');
cipher->set_key(SymmetricKey(all_zeros));
SecureVector<byte> package_key(cipher->BLOCK_SIZE);
SecureVector<byte> buf(cipher->BLOCK_SIZE);
// Copy the package key (masked with the block hashes)
copy_mem(&package_key[0],
input + (input_len - cipher->BLOCK_SIZE),
cipher->BLOCK_SIZE);
const u32bit blocks = ((input_len - 1) / cipher->BLOCK_SIZE);
// XOR the blocks into the package key bits
for(u32bit i = 0; i != blocks; ++i)
{
u32bit left = std::min<u32bit>(cipher->BLOCK_SIZE,
input_len - cipher->BLOCK_SIZE * (i+1));
buf.clear();
copy_mem(&buf[0], input + cipher->BLOCK_SIZE * i, left);
for(u32bit j = 0; j != 4; ++j)
buf[cipher->BLOCK_SIZE - 1 - j] ^= get_byte(3-j, i);
cipher->encrypt(buf);
xor_buf(&package_key[0], buf, cipher->BLOCK_SIZE);
}
Pipe pipe(new StreamCipher_Filter(new CTR_BE(cipher), package_key));
pipe.process_msg(input, input_len - cipher->BLOCK_SIZE);
pipe.read(output, pipe.remaining());
}
}
}
|