#include #ifdef BN_MP_IS_SQUARE_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is a library that provides multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library was designed directly after the MPI library by * Michael Fromberger but has been written from scratch with * additional optimizations in place. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org */ /* Check if remainders are possible squares - fast exclude non-squares */ static const char rem_128[128] = { 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1 }; static const char rem_105[105] = { 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1 }; /* Store non-zero to ret if arg is square, and zero if not */ int mp_is_square(mp_int *arg,int *ret) { int res; mp_digit c; mp_int t; unsigned long r; /* Default to Non-square :) */ *ret = MP_NO; if (arg->sign == MP_NEG) { return MP_VAL; } /* digits used? (TSD) */ if (arg->used == 0) { return MP_OKAY; } /* First check mod 128 (suppose that DIGIT_BIT is at least 7) */ if (rem_128[127 & DIGIT(arg,0)] == 1) { return MP_OKAY; } /* Next check mod 105 (3*5*7) */ if ((res = mp_mod_d(arg,105,&c)) != MP_OKAY) { return res; } if (rem_105[c] == 1) { return MP_OKAY; } if ((res = mp_init_set_int(&t,11L*13L*17L*19L*23L*29L*31L)) != MP_OKAY) { return res; } if ((res = mp_mod(arg,&t,&t)) != MP_OKAY) { goto ERR; } r = mp_get_int(&t); /* Check for other prime modules, note it's not an ERROR but we must * free "t" so the easiest way is to goto ERR. We know that res * is already equal to MP_OKAY from the mp_mod call */ if ( (1L<<(r%11)) & 0x5C4L ) goto ERR; if ( (1L<<(r%13)) & 0x9E4L ) goto ERR; if ( (1L<<(r%17)) & 0x5CE8L ) goto ERR; if ( (1L<<(r%19)) & 0x4F50CL ) goto ERR; if ( (1L<<(r%23)) & 0x7ACCA0L ) goto ERR; if ( (1L<<(r%29)) & 0xC2EDD0CL ) goto ERR; if ( (1L<<(r%31)) & 0x6DE2B848L ) goto ERR; /* Final check - is sqr(sqrt(arg)) == arg ? */ if ((res = mp_sqrt(arg,&t)) != MP_OKAY) { goto ERR; } if ((res = mp_sqr(&t,&t)) != MP_OKAY) { goto ERR; } *ret = (mp_cmp_mag(&t,arg) == MP_EQ) ? MP_YES : MP_NO; ERR:mp_clear(&t); return res; } #endif /* $Source: /root/tcl/repos-to-convert/tcl/libtommath/bn_mp_is_square.c,v $ */ /* $Revision: 1.1.1.2 $ */ /* $Date: 2005/09/26 16:31:56 $ */