static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)
{
    BIGNUM *n;
    BN_ULONG *ap, *np, *rp, n0, v, carry;
    int nl, max, i;
    n = &(mont->N);
    nl = n->top;
    if (nl == 0) {
        ret->top = 0;
        return (1);
    }
    max = (2 * nl);
    if (bn_wexpand(r, max) == NULL)
        return (0);
    r->neg ^= n->neg;
    np = n->d;
    rp = r->d;
    i = max - r->top;
    if (i)
        memset(&rp[r->top], 0, sizeof(*rp) * i);
    r->top = max;
    n0 = mont->n0[0];
    for (carry = 0, i = 0; i < nl; i++, rp++) {
        v = bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);
        v = (v + carry + rp[nl]) & BN_MASK2;
        carry |= (v != rp[nl]);
        carry &= (v <= rp[nl]);
        rp[nl] = v;
    }
    if (bn_wexpand(ret, nl) == NULL)
        return (0);
    ret->top = nl;
    ret->neg = r->neg;
    rp = ret->d;
    ap = &(r->d[nl]);
# define BRANCH_FREE 1
# if BRANCH_FREE
    {
        BN_ULONG *nrp;
        size_t m;
        v = bn_sub_words(rp, ap, np, nl) - carry;
        m = (0 - (size_t)v);
        nrp =
            (BN_ULONG *)(((PTR_SIZE_INT) rp & ~m) | ((PTR_SIZE_INT) ap & m));
        for (i = 0, nl -= 4; i < nl; i += 4) {
            BN_ULONG t1, t2, t3, t4;
            t1 = nrp[i + 0];
            t2 = nrp[i + 1];
            t3 = nrp[i + 2];
            ap[i + 0] = 0;
            t4 = nrp[i + 3];
            ap[i + 1] = 0;
            rp[i + 0] = t1;
            ap[i + 2] = 0;
            rp[i + 1] = t2;
            ap[i + 3] = 0;
            rp[i + 2] = t3;
            rp[i + 3] = t4;
        }
        for (nl += 4; i < nl; i++)
            rp[i] = nrp[i], ap[i] = 0;
    }
# else
    if (bn_sub_words(rp, ap, np, nl) - carry)
        memcpy(rp, ap, nl * sizeof(BN_ULONG));
# endif
    bn_correct_top(r);
    bn_correct_top(ret);
    bn_check_top(ret);
    return (1);
}
['int test_mod_exp_mont5(BIO *bp, BN_CTX *ctx)\n{\n    BIGNUM *a, *p, *m, *d, *e;\n    BN_MONT_CTX *mont;\n    a = BN_new();\n    p = BN_new();\n    m = BN_new();\n    d = BN_new();\n    e = BN_new();\n    mont = BN_MONT_CTX_new();\n    BN_bntest_rand(m, 1024, 0, 1);\n    BN_bntest_rand(a, 1024, 0, 0);\n    BN_zero(p);\n    if (!BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL))\n        return 0;\n    if (!BN_is_one(d)) {\n        fprintf(stderr, "Modular exponentiation test failed!\\n");\n        return 0;\n    }\n    BN_bntest_rand(p, 1024, 0, 0);\n    BN_zero(a);\n    if (!BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL))\n        return 0;\n    if (!BN_is_zero(d)) {\n        fprintf(stderr, "Modular exponentiation test failed!\\n");\n        return 0;\n    }\n    BN_one(a);\n    BN_MONT_CTX_set(mont, m, ctx);\n    if (!BN_from_montgomery(e, a, mont, ctx))\n        return 0;\n    if (!BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))\n        return 0;\n    if (!BN_mod_exp_simple(a, e, p, m, ctx))\n        return 0;\n    if (BN_cmp(a, d) != 0) {\n        fprintf(stderr, "Modular exponentiation test failed!\\n");\n        return 0;\n    }\n    BN_bntest_rand(e, 1024, 0, 0);\n    if (!BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))\n        return 0;\n    if (!BN_mod_exp_simple(a, e, p, m, ctx))\n        return 0;\n    if (BN_cmp(a, d) != 0) {\n        fprintf(stderr, "Modular exponentiation test failed!\\n");\n        return 0;\n    }\n    BN_MONT_CTX_free(mont);\n    BN_free(a);\n    BN_free(p);\n    BN_free(m);\n    BN_free(d);\n    BN_free(e);\n    return (1);\n}', 'int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)\n{\n    int ret = 0;\n    BIGNUM *Ri, *R;\n    if (BN_is_zero(mod))\n        return 0;\n    BN_CTX_start(ctx);\n    if ((Ri = BN_CTX_get(ctx)) == NULL)\n        goto err;\n    R = &(mont->RR);\n    if (!BN_copy(&(mont->N), mod))\n        goto err;\n    mont->N.neg = 0;\n#ifdef MONT_WORD\n    {\n        BIGNUM tmod;\n        BN_ULONG buf[2];\n        bn_init(&tmod);\n        tmod.d = buf;\n        tmod.dmax = 2;\n        tmod.neg = 0;\n        mont->ri = (BN_num_bits(mod) + (BN_BITS2 - 1)) / BN_BITS2 * BN_BITS2;\n# if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)\n        BN_zero(R);\n        if (!(BN_set_bit(R, 2 * BN_BITS2)))\n            goto err;\n        tmod.top = 0;\n        if ((buf[0] = mod->d[0]))\n            tmod.top = 1;\n        if ((buf[1] = mod->top > 1 ? mod->d[1] : 0))\n            tmod.top = 2;\n        if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)\n            goto err;\n        if (!BN_lshift(Ri, Ri, 2 * BN_BITS2))\n            goto err;\n        if (!BN_is_zero(Ri)) {\n            if (!BN_sub_word(Ri, 1))\n                goto err;\n        } else {\n            if (bn_expand(Ri, (int)sizeof(BN_ULONG) * 2) == NULL)\n                goto err;\n            Ri->neg = 0;\n            Ri->d[0] = BN_MASK2;\n            Ri->d[1] = BN_MASK2;\n            Ri->top = 2;\n        }\n        if (!BN_div(Ri, NULL, Ri, &tmod, ctx))\n            goto err;\n        mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;\n        mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0;\n# else\n        BN_zero(R);\n        if (!(BN_set_bit(R, BN_BITS2)))\n            goto err;\n        buf[0] = mod->d[0];\n        buf[1] = 0;\n        tmod.top = buf[0] != 0 ? 1 : 0;\n        if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)\n            goto err;\n        if (!BN_lshift(Ri, Ri, BN_BITS2))\n            goto err;\n        if (!BN_is_zero(Ri)) {\n            if (!BN_sub_word(Ri, 1))\n                goto err;\n        } else {\n            if (!BN_set_word(Ri, BN_MASK2))\n                goto err;\n        }\n        if (!BN_div(Ri, NULL, Ri, &tmod, ctx))\n            goto err;\n        mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;\n        mont->n0[1] = 0;\n# endif\n    }\n#else\n    {\n        mont->ri = BN_num_bits(&mont->N);\n        BN_zero(R);\n        if (!BN_set_bit(R, mont->ri))\n            goto err;\n        if ((BN_mod_inverse(Ri, R, &mont->N, ctx)) == NULL)\n            goto err;\n        if (!BN_lshift(Ri, Ri, mont->ri))\n            goto err;\n        if (!BN_sub_word(Ri, 1))\n            goto err;\n        if (!BN_div(&(mont->Ni), NULL, Ri, &mont->N, ctx))\n            goto err;\n    }\n#endif\n    BN_zero(&(mont->RR));\n    if (!BN_set_bit(&(mont->RR), mont->ri * 2))\n        goto err;\n    if (!BN_mod(&(mont->RR), &(mont->RR), &(mont->N), ctx))\n        goto err;\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\n    return ret;\n}', 'int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,\n                       BN_CTX *ctx)\n{\n    int retn = 0;\n#ifdef MONT_WORD\n    BIGNUM *t;\n    BN_CTX_start(ctx);\n    if ((t = BN_CTX_get(ctx)) && BN_copy(t, a))\n        retn = BN_from_montgomery_word(ret, t, mont);\n    BN_CTX_end(ctx);\n#else\n    BIGNUM *t1, *t2;\n    BN_CTX_start(ctx);\n    t1 = BN_CTX_get(ctx);\n    t2 = BN_CTX_get(ctx);\n    if (t1 == NULL || t2 == NULL)\n        goto err;\n    if (!BN_copy(t1, a))\n        goto err;\n    BN_mask_bits(t1, mont->ri);\n    if (!BN_mul(t2, t1, &mont->Ni, ctx))\n        goto err;\n    BN_mask_bits(t2, mont->ri);\n    if (!BN_mul(t1, t2, &mont->N, ctx))\n        goto err;\n    if (!BN_add(t2, a, t1))\n        goto err;\n    if (!BN_rshift(ret, t2, mont->ri))\n        goto err;\n    if (BN_ucmp(ret, &(mont->N)) >= 0) {\n        if (!BN_usub(ret, ret, &(mont->N)))\n            goto err;\n    }\n    retn = 1;\n    bn_check_top(ret);\n err:\n    BN_CTX_end(ctx);\n#endif\n    return (retn);\n}', 'static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)\n{\n    BIGNUM *n;\n    BN_ULONG *ap, *np, *rp, n0, v, carry;\n    int nl, max, i;\n    n = &(mont->N);\n    nl = n->top;\n    if (nl == 0) {\n        ret->top = 0;\n        return (1);\n    }\n    max = (2 * nl);\n    if (bn_wexpand(r, max) == NULL)\n        return (0);\n    r->neg ^= n->neg;\n    np = n->d;\n    rp = r->d;\n    i = max - r->top;\n    if (i)\n        memset(&rp[r->top], 0, sizeof(*rp) * i);\n    r->top = max;\n    n0 = mont->n0[0];\n    for (carry = 0, i = 0; i < nl; i++, rp++) {\n        v = bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);\n        v = (v + carry + rp[nl]) & BN_MASK2;\n        carry |= (v != rp[nl]);\n        carry &= (v <= rp[nl]);\n        rp[nl] = v;\n    }\n    if (bn_wexpand(ret, nl) == NULL)\n        return (0);\n    ret->top = nl;\n    ret->neg = r->neg;\n    rp = ret->d;\n    ap = &(r->d[nl]);\n# define BRANCH_FREE 1\n# if BRANCH_FREE\n    {\n        BN_ULONG *nrp;\n        size_t m;\n        v = bn_sub_words(rp, ap, np, nl) - carry;\n        m = (0 - (size_t)v);\n        nrp =\n            (BN_ULONG *)(((PTR_SIZE_INT) rp & ~m) | ((PTR_SIZE_INT) ap & m));\n        for (i = 0, nl -= 4; i < nl; i += 4) {\n            BN_ULONG t1, t2, t3, t4;\n            t1 = nrp[i + 0];\n            t2 = nrp[i + 1];\n            t3 = nrp[i + 2];\n            ap[i + 0] = 0;\n            t4 = nrp[i + 3];\n            ap[i + 1] = 0;\n            rp[i + 0] = t1;\n            ap[i + 2] = 0;\n            rp[i + 1] = t2;\n            ap[i + 3] = 0;\n            rp[i + 2] = t3;\n            rp[i + 3] = t4;\n        }\n        for (nl += 4; i < nl; i++)\n            rp[i] = nrp[i], ap[i] = 0;\n    }\n# else\n    if (bn_sub_words(rp, ap, np, nl) - carry)\n        memcpy(rp, ap, nl * sizeof(BN_ULONG));\n# endif\n    bn_correct_top(r);\n    bn_correct_top(ret);\n    bn_check_top(ret);\n    return (1);\n}', 'BIGNUM *bn_wexpand(BIGNUM *a, int words)\n{\n    return (words <= a->dmax) ? a : bn_expand2(a, words);\n}']