Botan 3.5.0 Crypto and TLS for C&
poly_dbl.cpp
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1/*
2* (C) 2017,2018 Jack Lloyd
3*
5*/
6
7#include <botan/internal/poly_dbl.h>
8
9#include <botan/exceptn.h>
10#include <botan/internal/ct_utils.h>
12
13namespace Botan {
14
15namespace {
16
17/*
18* The minimum weight irreducible binary polynomial of size n
19*
20* See "Table of Low-Weight Binary Irreducible Polynomials"
21* by Gadiel Seroussi, HP Labs Tech Report HPL-98-135
22* http://www.hpl.hp.com/techreports/98/HPL-98-135.pdf
23*/
24enum class MinWeightPolynomial : uint32_t {
25 P64 = 0x1B,
26 P128 = 0x87,
27 P192 = 0x87,
28 P256 = 0x425,
29 P512 = 0x125,
30 P1024 = 0x80043,
31};
32
33/**
34* If the top bit of c is set, returns the carry (the polynomial)
35*
36* Otherwise returns zero.
37*/
38template <MinWeightPolynomial P>
39inline uint64_t return_carry(uint64_t c) {
41}
42
43template <size_t LIMBS, MinWeightPolynomial P>
44void poly_double(uint8_t out[], const uint8_t in[]) {
45 uint64_t W[LIMBS];
47
48 const uint64_t carry = return_carry<P>(W[0]);
49
50 if constexpr(LIMBS > 0) {
51 for(size_t i = 0; i != LIMBS - 1; ++i) {
52 W[i] = (W[i] << 1) ^ (W[i + 1] >> 63);
53 }
54 }
55
56 W[LIMBS - 1] = (W[LIMBS - 1] << 1) ^ carry;
57
58 copy_out_be(std::span(out, LIMBS * 8), W);
59}
60
61template <size_t LIMBS, MinWeightPolynomial P>
62void poly_double_le(uint8_t out[], const uint8_t in[]) {
63 uint64_t W[LIMBS];
65
66 const uint64_t carry = return_carry<P>(W[LIMBS - 1]);
67
68 if constexpr(LIMBS > 0) {
69 for(size_t i = 0; i != LIMBS - 1; ++i) {
70 W[LIMBS - 1 - i] = (W[LIMBS - 1 - i] << 1) ^ (W[LIMBS - 2 - i] >> 63);
71 }
72 }
73
74 W[0] = (W[0] << 1) ^ carry;
75
76 copy_out_le(std::span(out, LIMBS * 8), W);
77}
78
79} // namespace
80
81void poly_double_n(uint8_t out[], const uint8_t in[], size_t n) {
82 switch(n) {
83 case 8:
84 return poly_double<1, MinWeightPolynomial::P64>(out, in);
85 case 16:
86 return poly_double<2, MinWeightPolynomial::P128>(out, in);
87 case 24:
88 return poly_double<3, MinWeightPolynomial::P192>(out, in);
89 case 32:
90 return poly_double<4, MinWeightPolynomial::P256>(out, in);
91 case 64:
92 return poly_double<8, MinWeightPolynomial::P512>(out, in);
93 case 128:
94 return poly_double<16, MinWeightPolynomial::P1024>(out, in);
95 default:
96 throw Invalid_Argument("Unsupported size for poly_double_n");
97 }
98}
99
100void poly_double_n_le(uint8_t out[], const uint8_t in[], size_t n) {
101 switch(n) {
102 case 8:
103 return poly_double_le<1, MinWeightPolynomial::P64>(out, in);
104 case 16:
105 return poly_double_le<2, MinWeightPolynomial::P128>(out, in);
106 case 24:
107 return poly_double_le<3, MinWeightPolynomial::P192>(out, in);
108 case 32:
109 return poly_double_le<4, MinWeightPolynomial::P256>(out, in);
110 case 64:
111 return poly_double_le<8, MinWeightPolynomial::P512>(out, in);
112 case 128:
113 return poly_double_le<16, MinWeightPolynomial::P1024>(out, in);
114 default:
115 throw Invalid_Argument("Unsupported size for poly_double_n_le");
116 }
117}
118
119void xts_update_tweak_block(uint8_t tweak[], size_t BS, size_t blocks_in_tweak) {
120 if(BS == 16) {
121 constexpr size_t LIMBS = 2;
122
123 uint64_t W[LIMBS];
125
126 for(size_t i = 1; i < blocks_in_tweak; ++i) {
127 const uint64_t carry = return_carry<MinWeightPolynomial::P128>(W[1]);
128 W[1] = (W[1] << 1) ^ (W[0] >> 63);
129 W[0] = (W[0] << 1) ^ carry;
130 copy_out_le(std::span(&tweak[i * BS], 2 * 8), W);
131 }
132 } else {
133 for(size_t i = 1; i < blocks_in_tweak; ++i) {
134 const uint8_t* prev = &tweak[(i - 1) * BS];
135 uint8_t* cur = &tweak[i * BS];
136 poly_double_n_le(cur, prev, BS);
137 }
138 }
139}
140
141} // namespace Botan
static constexpr Mask< T > expand_top_bit(T v)
Definition ct_utils.h:231
void copy_out_be(std::span< uint8_t > out, InR &&in)