annotate libtommath/bn_mp_montgomery_reduce.c @ 1653:76189c9ffea2

External Public-Key Authentication API (#72) * Implemented dynamic loading of an external plug-in shared library to delegate public key authentication * Moved conditional compilation of the plugin infrastructure into the configure.ac script to be able to add -ldl to dropbear build only when the flag is enabled * Added tags file to the ignore list * Updated API to have the constructor to return function pointers in the pliugin instance. Added support for passing user name to the checkpubkey function. Added options to the session returned by the plugin and have dropbear to parse and process them * Added -rdynamic to the linker flags when EPKA is enabled * Changed the API to pass a previously created session to the checkPubKey function (created during preauth) * Added documentation to the API * Added parameter addrstring to plugin creation function * Modified the API to retrieve the auth options. Instead of having them as field of the EPKASession struct, they are stored internally (plugin-dependent) in the plugin/session and retrieved through a pointer to a function (in the session) * Changed option string to be a simple char * instead of unsigned char *
author fabriziobertocci <fabriziobertocci@gmail.com>
date Wed, 15 May 2019 09:43:57 -0400
parents 8bba51a55704
children f52919ffd3b1
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 #include <tommath_private.h>
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2 #ifdef BN_MP_MONTGOMERY_REDUCE_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 *
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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 xR**-1 == x (mod N) via Montgomery Reduction */
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19 int
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20 mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho)
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21 {
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22 int ix, res, digs;
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23 mp_digit mu;
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24
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25 /* can the fast reduction [comba] method be used?
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26 *
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27 * Note that unlike in mul you're safely allowed *less*
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28 * than the available columns [255 per default] since carries
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29 * are fixed up in the inner loop.
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30 */
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31 digs = (n->used * 2) + 1;
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32 if ((digs < MP_WARRAY) &&
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33 (n->used <
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34 (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
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35 return fast_mp_montgomery_reduce (x, n, rho);
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36 }
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37
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38 /* grow the input as required */
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39 if (x->alloc < digs) {
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40 if ((res = mp_grow (x, digs)) != MP_OKAY) {
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41 return res;
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42 }
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43 }
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44 x->used = digs;
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45
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46 for (ix = 0; ix < n->used; ix++) {
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47 /* mu = ai * rho mod b
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48 *
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49 * The value of rho must be precalculated via
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50 * montgomery_setup() such that
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51 * it equals -1/n0 mod b this allows the
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52 * following inner loop to reduce the
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53 * input one digit at a time
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54 */
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55 mu = (mp_digit) (((mp_word)x->dp[ix] * (mp_word)rho) & MP_MASK);
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56
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57 /* a = a + mu * m * b**i */
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58 {
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59 int iy;
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60 mp_digit *tmpn, *tmpx, u;
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61 mp_word r;
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62
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63 /* alias for digits of the modulus */
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64 tmpn = n->dp;
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65
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66 /* alias for the digits of x [the input] */
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67 tmpx = x->dp + ix;
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68
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69 /* set the carry to zero */
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70 u = 0;
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71
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72 /* Multiply and add in place */
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73 for (iy = 0; iy < n->used; iy++) {
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74 /* compute product and sum */
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75 r = ((mp_word)mu * (mp_word)*tmpn++) +
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76 (mp_word) u + (mp_word) *tmpx;
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77
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78 /* get carry */
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79 u = (mp_digit)(r >> ((mp_word) DIGIT_BIT));
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80
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81 /* fix digit */
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82 *tmpx++ = (mp_digit)(r & ((mp_word) MP_MASK));
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83 }
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84 /* At this point the ix'th digit of x should be zero */
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85
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86
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87 /* propagate carries upwards as required*/
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88 while (u != 0) {
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89 *tmpx += u;
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90 u = *tmpx >> DIGIT_BIT;
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91 *tmpx++ &= MP_MASK;
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92 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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93 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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94 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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95
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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96 /* at this point the n.used'th least
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Matt Johnston <matt@ucc.asn.au>
parents:
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97 * significant digits of x are all zero
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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98 * which means we can shift x to the
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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99 * right by n.used digits and the
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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100 * residue is unchanged.
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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101 */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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102
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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103 /* x = x/b**n.used */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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104 mp_clamp(x);
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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105 mp_rshd (x, n->used);
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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106
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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107 /* if x >= n then x = x - n */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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108 if (mp_cmp_mag (x, n) != MP_LT) {
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Matt Johnston <matt@ucc.asn.au>
parents:
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109 return s_mp_sub (x, n, x);
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Matt Johnston <matt@ucc.asn.au>
parents:
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110 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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111
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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112 return MP_OKAY;
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Matt Johnston <matt@ucc.asn.au>
parents:
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113 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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114 #endif
389
5ff8218bcee9 propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e)
Matt Johnston <matt@ucc.asn.au>
parents: 284
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115
1470
8bba51a55704 Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents: 1436
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116 /* ref: $Format:%D$ */
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Matt Johnston <matt@ucc.asn.au>
parents: 1436
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117 /* git commit: $Format:%H$ */
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118 /* commit time: $Format:%ai$ */