Mercurial > dropbear
view libtommath/bn_mp_is_square.c @ 1812:552bb9b4f16a
Make releases tarballs more deterministic
Not fully tested on different systems yet
author | Matt Johnston <matt@ucc.asn.au> |
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date | Tue, 30 Mar 2021 22:08:14 +0800 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_MP_IS_SQUARE_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* 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 */ mp_err mp_is_square(const mp_int *arg, mp_bool *ret) { mp_err err; mp_digit c; mp_int t; unsigned long r; /* Default to Non-square :) */ *ret = MP_NO; if (arg->sign == MP_NEG) { return MP_VAL; } if (MP_IS_ZERO(arg)) { return MP_OKAY; } /* First check mod 128 (suppose that MP_DIGIT_BIT is at least 7) */ if (rem_128[127u & arg->dp[0]] == (char)1) { return MP_OKAY; } /* Next check mod 105 (3*5*7) */ if ((err = mp_mod_d(arg, 105uL, &c)) != MP_OKAY) { return err; } if (rem_105[c] == (char)1) { return MP_OKAY; } if ((err = mp_init_u32(&t, 11u*13u*17u*19u*23u*29u*31u)) != MP_OKAY) { return err; } if ((err = mp_mod(arg, &t, &t)) != MP_OKAY) { goto LBL_ERR; } r = mp_get_u32(&t); /* Check for other prime modules, note it's not an ERROR but we must * free "t" so the easiest way is to goto LBL_ERR. We know that err * is already equal to MP_OKAY from the mp_mod call */ if (((1uL<<(r%11uL)) & 0x5C4uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%13uL)) & 0x9E4uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%17uL)) & 0x5CE8uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%19uL)) & 0x4F50CuL) != 0uL) goto LBL_ERR; if (((1uL<<(r%23uL)) & 0x7ACCA0uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%29uL)) & 0xC2EDD0CuL) != 0uL) goto LBL_ERR; if (((1uL<<(r%31uL)) & 0x6DE2B848uL) != 0uL) goto LBL_ERR; /* Final check - is sqr(sqrt(arg)) == arg ? */ if ((err = mp_sqrt(arg, &t)) != MP_OKAY) { goto LBL_ERR; } if ((err = mp_sqr(&t, &t)) != MP_OKAY) { goto LBL_ERR; } *ret = (mp_cmp_mag(&t, arg) == MP_EQ) ? MP_YES : MP_NO; LBL_ERR: mp_clear(&t); return err; } #endif