Mercurial > dropbear
annotate libtommath/bn_fast_mp_invmod.c @ 1493:72fd994fe7bd
Update build instructions for localoptions, and tidy
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 14 Feb 2018 00:24:32 +0800 |
parents | 8bba51a55704 |
children | f52919ffd3b1 |
rev | line source |
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1436 | 1 #include <tommath_private.h> |
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2 #ifdef BN_FAST_MP_INVMOD_C |
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
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4 * |
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5 * LibTomMath is a library that provides multiple-precision |
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6 * integer arithmetic as well as number theoretic functionality. |
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7 * |
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8 * The library was designed directly after the MPI library by |
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9 * Michael Fromberger but has been written from scratch with |
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10 * additional optimizations in place. |
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11 * |
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12 * The library is free for all purposes without any express |
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13 * guarantee it works. |
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14 * |
1436 | 15 * Tom St Denis, [email protected], http://libtom.org |
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16 */ |
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17 |
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18 /* computes the modular inverse via binary extended euclidean algorithm, |
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19 * that is c = 1/a mod b |
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20 * |
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21 * Based on slow invmod except this is optimized for the case where b is |
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22 * odd as per HAC Note 14.64 on pp. 610 |
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23 */ |
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24 int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c) |
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25 { |
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26 mp_int x, y, u, v, B, D; |
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27 int res, neg; |
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28 |
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29 /* 2. [modified] b must be odd */ |
1436 | 30 if (mp_iseven (b) == MP_YES) { |
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31 return MP_VAL; |
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32 } |
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33 |
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34 /* init all our temps */ |
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35 if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) { |
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36 return res; |
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37 } |
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38 |
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39 /* x == modulus, y == value to invert */ |
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40 if ((res = mp_copy (b, &x)) != MP_OKAY) { |
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41 goto LBL_ERR; |
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42 } |
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43 |
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44 /* we need y = |a| */ |
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45 if ((res = mp_mod (a, b, &y)) != MP_OKAY) { |
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46 goto LBL_ERR; |
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47 } |
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48 |
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49 /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ |
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50 if ((res = mp_copy (&x, &u)) != MP_OKAY) { |
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51 goto LBL_ERR; |
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52 } |
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53 if ((res = mp_copy (&y, &v)) != MP_OKAY) { |
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54 goto LBL_ERR; |
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55 } |
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56 mp_set (&D, 1); |
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57 |
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58 top: |
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59 /* 4. while u is even do */ |
1436 | 60 while (mp_iseven (&u) == MP_YES) { |
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61 /* 4.1 u = u/2 */ |
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62 if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { |
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63 goto LBL_ERR; |
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64 } |
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65 /* 4.2 if B is odd then */ |
1436 | 66 if (mp_isodd (&B) == MP_YES) { |
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67 if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { |
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68 goto LBL_ERR; |
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69 } |
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70 } |
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71 /* B = B/2 */ |
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72 if ((res = mp_div_2 (&B, &B)) != MP_OKAY) { |
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73 goto LBL_ERR; |
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74 } |
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75 } |
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76 |
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77 /* 5. while v is even do */ |
1436 | 78 while (mp_iseven (&v) == MP_YES) { |
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79 /* 5.1 v = v/2 */ |
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80 if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { |
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81 goto LBL_ERR; |
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82 } |
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83 /* 5.2 if D is odd then */ |
1436 | 84 if (mp_isodd (&D) == MP_YES) { |
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85 /* D = (D-x)/2 */ |
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86 if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { |
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87 goto LBL_ERR; |
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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
88 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
89 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
90 /* D = D/2 */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
91 if ((res = mp_div_2 (&D, &D)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
92 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
93 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
94 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
95 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
96 /* 6. if u >= v then */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
97 if (mp_cmp (&u, &v) != MP_LT) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
98 /* u = u - v, B = B - D */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
99 if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
100 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
101 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
102 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
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103 if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
104 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
105 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
106 } else { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
107 /* v - v - u, D = D - B */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
108 if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
109 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
110 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
111 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
112 if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
113 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
114 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
115 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
116 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
117 /* if not zero goto step 4 */ |
1436 | 118 if (mp_iszero (&u) == MP_NO) { |
284
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
119 goto top; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
120 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
121 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
122 /* now a = C, b = D, gcd == g*v */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
123 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
124 /* if v != 1 then there is no inverse */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
125 if (mp_cmp_d (&v, 1) != MP_EQ) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
126 res = MP_VAL; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
127 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
128 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
129 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
130 /* b is now the inverse */ |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
131 neg = a->sign; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
132 while (D.sign == MP_NEG) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
133 if ((res = mp_add (&D, b, &D)) != MP_OKAY) { |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
134 goto LBL_ERR; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
135 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
136 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
137 mp_exch (&D, c); |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
138 c->sign = neg; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
139 res = MP_OKAY; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
140 |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
141 LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL); |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
142 return res; |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
143 } |
eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff
changeset
|
144 #endif |
389
5ff8218bcee9
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e)
Matt Johnston <matt@ucc.asn.au>
parents:
284
diff
changeset
|
145 |
1470
8bba51a55704
Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents:
1436
diff
changeset
|
146 /* ref: $Format:%D$ */ |
8bba51a55704
Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents:
1436
diff
changeset
|
147 /* git commit: $Format:%H$ */ |
8bba51a55704
Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents:
1436
diff
changeset
|
148 /* commit time: $Format:%ai$ */ |