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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
/*
* CMAC
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cmac.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
/*
* Perform CMAC's multiplication in GF(2^n)
*/
SecureVector<byte> CMAC::poly_double(const MemoryRegion<byte>& in,
byte polynomial)
{
const bool do_xor = (in[0] & 0x80) ? true : false;
SecureVector<byte> out = in;
byte carry = 0;
for(size_t i = out.size(); i != 0; --i)
{
byte temp = out[i-1];
out[i-1] = (temp << 1) | carry;
carry = (temp >> 7);
}
if(do_xor)
out[out.size()-1] ^= polynomial;
return out;
}
/*
* Update an CMAC Calculation
*/
void CMAC::add_data(const byte input[], size_t length)
{
buffer.copy(position, input, length);
if(position + length > OUTPUT_LENGTH)
{
xor_buf(state, buffer, OUTPUT_LENGTH);
e->encrypt(state);
input += (OUTPUT_LENGTH - position);
length -= (OUTPUT_LENGTH - position);
while(length > OUTPUT_LENGTH)
{
xor_buf(state, input, OUTPUT_LENGTH);
e->encrypt(state);
input += OUTPUT_LENGTH;
length -= OUTPUT_LENGTH;
}
buffer.copy(input, length);
position = 0;
}
position += length;
}
/*
* Finalize an CMAC Calculation
*/
void CMAC::final_result(byte mac[])
{
xor_buf(state, buffer, position);
if(position == OUTPUT_LENGTH)
{
xor_buf(state, B, OUTPUT_LENGTH);
}
else
{
state[position] ^= 0x80;
xor_buf(state, P, OUTPUT_LENGTH);
}
e->encrypt(state);
for(size_t i = 0; i != OUTPUT_LENGTH; ++i)
mac[i] = state[i];
zeroise(state);
zeroise(buffer);
position = 0;
}
/*
* CMAC Key Schedule
*/
void CMAC::key_schedule(const byte key[], u32bit length)
{
clear();
e->set_key(key, length);
e->encrypt(B);
B = poly_double(B, polynomial);
P = poly_double(B, polynomial);
}
/*
* Clear memory of sensitive data
*/
void CMAC::clear()
{
e->clear();
zeroise(state);
zeroise(buffer);
zeroise(B);
zeroise(P);
position = 0;
}
/*
* Return the name of this type
*/
std::string CMAC::name() const
{
return "CMAC(" + e->name() + ")";
}
/*
* Return a clone of this object
*/
MessageAuthenticationCode* CMAC::clone() const
{
return new CMAC(e->clone());
}
/*
* CMAC Constructor
*/
CMAC::CMAC(BlockCipher* e_in) :
MessageAuthenticationCode(e_in->BLOCK_SIZE,
e_in->MINIMUM_KEYLENGTH,
e_in->MAXIMUM_KEYLENGTH,
e_in->KEYLENGTH_MULTIPLE),
e(e_in)
{
if(e->BLOCK_SIZE == 16)
polynomial = 0x87;
else if(e->BLOCK_SIZE == 8)
polynomial = 0x1B;
else
throw Invalid_Argument("CMAC cannot use the cipher " + e->name());
state.resize(OUTPUT_LENGTH);
buffer.resize(OUTPUT_LENGTH);
B.resize(OUTPUT_LENGTH);
P.resize(OUTPUT_LENGTH);
position = 0;
}
/*
* CMAC Destructor
*/
CMAC::~CMAC()
{
delete e;
}
}
|
