Copyright © 2001 - 2002 SILC Project SILC Project Website | SILC Toolkit Reference Manual

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Function silc_mp_modinv SYNOPSIS
        void silc_mp_modinv(SilcMPInt *inv, SilcMPInt *a, SilcMPInt *n);
DESCRIPTION
        Find multiplicative inverse using Euclid's extended algorithm.
        Computes inverse such that a * inv mod n = 1, where 0 < a < n.
        Algorithm goes like this:

        g(0) = n    v(0) = 0
        g(1) = a    v(1) = 1

        y = g(i-1) / g(i)
        g(i+1) = g(i-1) - y * g(i) = g(i)-1 mod g(i)
        v(i+1) = v(i-1) - y * v(i)

        do until g(i) = 0, then inverse = v(i-1). If inverse is negative then n,
        is added to inverse making it positive again. (Sometimes the algorithm
        has a variable u defined too and it behaves just like v, except that
        initalize values are swapped (i.e. u(0) = 1, u(1) = 0). However, u is
        not needed by the algorithm so it does not have to be included.)
SilcMPAPI SilcMPInt silc_mp_init silc_mp_uninit silc_mp_size silc_mp_sizeinbase silc_mp_set silc_mp_set_ui silc_mp_set_si silc_mp_set_str silc_mp_get_ui silc_mp_get_str silc_mp_add silc_mp_add_ui silc_mp_sub silc_mp_sub_ui silc_mp_mul silc_mp_mul_ui silc_mp_mul_2exp silc_mp_sqrt silc_mp_div silc_mp_div_ui silc_mp_div_qr silc_mp_div_2exp silc_mp_div_2exp_qr silc_mp_mod silc_mp_mod_ui silc_mp_mod_2exp silc_mp_pow silc_mp_pow_ui silc_mp_pow_mod silc_mp_pow_mod_ui silc_mp_modinv silc_mp_gcd silc_mp_gcdext silc_mp_cmp silc_mp_cmp_si silc_mp_cmp_ui silc_mp_mp2bin silc_mp_mp2bin_noalloc silc_mp_bin2mp silc_mp_abs silc_mp_neg silc_mp_and silc_mp_or silc_mp_xor

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