/src/botan/build/include/botan/internal/gf2m_small_m.h
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1 | | /* |
2 | | * (C) Copyright Projet SECRET, INRIA, Rocquencourt |
3 | | * (C) Bhaskar Biswas and Nicolas Sendrier |
4 | | * |
5 | | * (C) 2014 cryptosource GmbH |
6 | | * (C) 2014 Falko Strenzke fstrenzke@cryptosource.de |
7 | | * |
8 | | * Botan is released under the Simplified BSD License (see license.txt) |
9 | | * |
10 | | */ |
11 | | |
12 | | #ifndef BOTAN_GF2M_SMALL_M_H_ |
13 | | #define BOTAN_GF2M_SMALL_M_H_ |
14 | | |
15 | | #include <botan/types.h> |
16 | | #include <vector> |
17 | | |
18 | | namespace Botan { |
19 | | |
20 | | typedef uint16_t gf2m; |
21 | | |
22 | | /** |
23 | | * GF(2^m) field for m = [2...16] |
24 | | */ |
25 | | class BOTAN_TEST_API GF2m_Field |
26 | | { |
27 | | public: |
28 | | explicit GF2m_Field(size_t extdeg); |
29 | | |
30 | | gf2m gf_mul(gf2m x, gf2m y) const |
31 | 0 | { |
32 | 0 | return ((x) ? gf_mul_fast(x, y) : 0); |
33 | 0 | } |
34 | | |
35 | | gf2m gf_square(gf2m x) const |
36 | 0 | { |
37 | 0 | return ((x) ? gf_exp(_gf_modq_1(gf_log(x) << 1)) : 0); |
38 | 0 | } |
39 | | |
40 | | gf2m square_rr(gf2m x) const |
41 | 0 | { |
42 | 0 | return _gf_modq_1(x << 1); |
43 | 0 | } |
44 | | |
45 | | gf2m gf_mul_fast(gf2m x, gf2m y) const |
46 | 0 | { |
47 | 0 | return ((y) ? gf_exp(_gf_modq_1(gf_log(x) + gf_log(y))) : 0); |
48 | 0 | } |
49 | | |
50 | | /* |
51 | | naming convention of GF(2^m) field operations: |
52 | | l logarithmic, unreduced |
53 | | r logarithmic, reduced |
54 | | n normal, non-zero |
55 | | z normal, might be zero |
56 | | */ |
57 | | |
58 | | gf2m gf_mul_lll(gf2m a, gf2m b) const |
59 | 0 | { |
60 | 0 | return (a + b); |
61 | 0 | } |
62 | | |
63 | | gf2m gf_mul_rrr(gf2m a, gf2m b) const |
64 | 0 | { |
65 | 0 | return (_gf_modq_1(gf_mul_lll(a, b))); |
66 | 0 | } |
67 | | |
68 | | gf2m gf_mul_nrr(gf2m a, gf2m b) const |
69 | 0 | { |
70 | 0 | return (gf_exp(gf_mul_rrr(a, b))); |
71 | 0 | } |
72 | | |
73 | | gf2m gf_mul_rrn(gf2m a, gf2m y) const |
74 | 0 | { |
75 | 0 | return _gf_modq_1(gf_mul_lll(a, gf_log(y))); |
76 | 0 | } |
77 | | |
78 | | gf2m gf_mul_rnr(gf2m y, gf2m a) const |
79 | 0 | { |
80 | 0 | return gf_mul_rrn(a, y); |
81 | 0 | } |
82 | | |
83 | | gf2m gf_mul_lnn(gf2m x, gf2m y) const |
84 | 0 | { |
85 | 0 | return (gf_log(x) + gf_log(y)); |
86 | 0 | } |
87 | | |
88 | | gf2m gf_mul_rnn(gf2m x, gf2m y) const |
89 | 0 | { |
90 | 0 | return _gf_modq_1(gf_mul_lnn(x, y)); |
91 | 0 | } |
92 | | |
93 | | gf2m gf_mul_nrn(gf2m a, gf2m y) const |
94 | 0 | { |
95 | 0 | return gf_exp(_gf_modq_1((a) + gf_log(y))); |
96 | 0 | } |
97 | | |
98 | | /** |
99 | | * zero operand allowed |
100 | | */ |
101 | | gf2m gf_mul_zrz(gf2m a, gf2m y) const |
102 | 0 | { |
103 | 0 | return ( (y == 0) ? 0 : gf_mul_nrn(a, y) ); |
104 | 0 | } |
105 | | |
106 | | gf2m gf_mul_zzr(gf2m a, gf2m y) const |
107 | 0 | { |
108 | 0 | return gf_mul_zrz(y, a); |
109 | 0 | } |
110 | | |
111 | | /** |
112 | | * non-zero operand |
113 | | */ |
114 | | gf2m gf_mul_nnr(gf2m y, gf2m a) const |
115 | 0 | { |
116 | 0 | return gf_mul_nrn(a, y); |
117 | 0 | } |
118 | | |
119 | | gf2m gf_sqrt(gf2m x) const |
120 | 0 | { |
121 | 0 | return ((x) ? gf_exp(_gf_modq_1(gf_log(x) << (get_extension_degree()-1))) : 0); |
122 | 0 | } |
123 | | |
124 | | gf2m gf_div_rnn(gf2m x, gf2m y) const |
125 | 0 | { |
126 | 0 | return _gf_modq_1(gf_log(x) - gf_log(y)); |
127 | 0 | } |
128 | | |
129 | | gf2m gf_div_rnr(gf2m x, gf2m b) const |
130 | 0 | { |
131 | 0 | return _gf_modq_1(gf_log(x) - b); |
132 | 0 | } |
133 | | |
134 | | gf2m gf_div_nrr(gf2m a, gf2m b) const |
135 | 0 | { |
136 | 0 | return gf_exp(_gf_modq_1(a - b)); |
137 | 0 | } |
138 | | |
139 | | gf2m gf_div_zzr(gf2m x, gf2m b) const |
140 | 0 | { |
141 | 0 | return ((x) ? gf_exp(_gf_modq_1(gf_log(x) - b)) : 0); |
142 | 0 | } |
143 | | |
144 | | gf2m gf_inv(gf2m x) const |
145 | 0 | { |
146 | 0 | return gf_exp(gf_ord() - gf_log(x)); |
147 | 0 | } |
148 | | |
149 | | gf2m gf_inv_rn(gf2m x) const |
150 | 0 | { |
151 | 0 | return (gf_ord() - gf_log(x)); |
152 | 0 | } |
153 | | |
154 | | gf2m gf_square_ln(gf2m x) const |
155 | 0 | { |
156 | 0 | return gf_log(x) << 1; |
157 | 0 | } |
158 | | |
159 | | gf2m gf_square_rr(gf2m a) const |
160 | 0 | { |
161 | 0 | return a << 1; |
162 | 0 | } |
163 | | |
164 | | gf2m gf_l_from_n(gf2m x) const |
165 | 0 | { |
166 | 0 | return gf_log(x); |
167 | 0 | } |
168 | | |
169 | | gf2m gf_div(gf2m x, gf2m y) const; |
170 | | |
171 | | gf2m gf_exp(gf2m i) const |
172 | 0 | { |
173 | 0 | return m_gf_exp_table.at(i); /* alpha^i */ |
174 | 0 | } |
175 | | |
176 | | gf2m gf_log(gf2m i) const |
177 | 0 | { |
178 | 0 | return m_gf_log_table.at(i); /* return i when x=alpha^i */ |
179 | 0 | } |
180 | | |
181 | | gf2m gf_ord() const |
182 | 0 | { |
183 | 0 | return m_gf_multiplicative_order; |
184 | 0 | } |
185 | | |
186 | | size_t get_extension_degree() const |
187 | 0 | { |
188 | 0 | return m_gf_extension_degree; |
189 | 0 | } |
190 | | |
191 | | gf2m get_cardinality() const |
192 | 0 | { |
193 | 0 | return static_cast<gf2m>(1 << get_extension_degree()); |
194 | 0 | } |
195 | | |
196 | | private: |
197 | | gf2m _gf_modq_1(int32_t d) const |
198 | 0 | { |
199 | | /* residual modulo q-1 |
200 | | when -q < d < 0, we get (q-1+d) |
201 | | when 0 <= d < q, we get (d) |
202 | | when q <= d < 2q-1, we get (d-q+1) |
203 | | */ |
204 | 0 | return static_cast<gf2m>(((d) & gf_ord()) + ((d) >> get_extension_degree())); |
205 | 0 | } |
206 | | |
207 | | const size_t m_gf_extension_degree; |
208 | | const gf2m m_gf_multiplicative_order; |
209 | | const std::vector<gf2m>& m_gf_log_table; |
210 | | const std::vector<gf2m>& m_gf_exp_table; |
211 | | }; |
212 | | |
213 | | uint32_t encode_gf2m(gf2m to_enc, uint8_t* mem); |
214 | | |
215 | | gf2m decode_gf2m(const uint8_t* mem); |
216 | | |
217 | | } |
218 | | |
219 | | #endif |