/src/openssl111/crypto/bn/bn_mul.c

Source (jump to first uncovered line)
/*
 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the OpenSSL license (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include <assert.h>
#include "internal/cryptlib.h"
#include "bn_local.h"

#if defined(OPENSSL_NO_ASM) || !defined(OPENSSL_BN_ASM_PART_WORDS)
/*
 * Here follows specialised variants of bn_add_words() and bn_sub_words().
 * They have the property performing operations on arrays of different sizes.
 * The sizes of those arrays is expressed through cl, which is the common
 * length ( basically, min(len(a),len(b)) ), and dl, which is the delta
 * between the two lengths, calculated as len(a)-len(b). All lengths are the
 * number of BN_ULONGs...  For the operations that require a result array as
 * parameter, it must have the length cl+abs(dl). These functions should
 * probably end up in bn_asm.c as soon as there are assembler counterparts
 * for the systems that use assembler files.
 */

BN_ULONG bn_sub_part_words(BN_ULONG *r,
                           const BN_ULONG *a, const BN_ULONG *b,
                           int cl, int dl)
{
    BN_ULONG c, t;

    assert(cl >= 0);
    c = bn_sub_words(r, a, b, cl);

    if (dl == 0)
        return c;

    r += cl;
    a += cl;
    b += cl;

    if (dl < 0) {
        for (;;) {
            t = b[0];
            r[0] = (0 - t - c) & BN_MASK2;
            if (t != 0)
                c = 1;
            if (++dl >= 0)
                break;

            t = b[1];
            r[1] = (0 - t - c) & BN_MASK2;
            if (t != 0)
                c = 1;
            if (++dl >= 0)
                break;

            t = b[2];
            r[2] = (0 - t - c) & BN_MASK2;
            if (t != 0)
                c = 1;
            if (++dl >= 0)
                break;

            t = b[3];
            r[3] = (0 - t - c) & BN_MASK2;
            if (t != 0)
                c = 1;
            if (++dl >= 0)
                break;

            b += 4;
            r += 4;
        }
    } else {
        int save_dl = dl;
        while (c) {
            t = a[0];
            r[0] = (t - c) & BN_MASK2;
            if (t != 0)
                c = 0;
            if (--dl <= 0)
                break;

            t = a[1];
            r[1] = (t - c) & BN_MASK2;
            if (t != 0)
                c = 0;
            if (--dl <= 0)
                break;

            t = a[2];
            r[2] = (t - c) & BN_MASK2;
            if (t != 0)
                c = 0;
            if (--dl <= 0)
                break;

            t = a[3];
            r[3] = (t - c) & BN_MASK2;
            if (t != 0)
                c = 0;
            if (--dl <= 0)
                break;

            save_dl = dl;
            a += 4;
            r += 4;
        }
        if (dl > 0) {
            if (save_dl > dl) {
                switch (save_dl - dl) {
                case 1:
                    r[1] = a[1];
                    if (--dl <= 0)
                        break;
                    /* fall thru */
                case 2:
                    r[2] = a[2];
                    if (--dl <= 0)
                        break;
                    /* fall thru */
                case 3:
                    r[3] = a[3];
                    if (--dl <= 0)
                        break;
                }
                a += 4;
                r += 4;
            }
        }
        if (dl > 0) {
            for (;;) {
                r[0] = a[0];
                if (--dl <= 0)
                    break;
                r[1] = a[1];
                if (--dl <= 0)
                    break;
                r[2] = a[2];
                if (--dl <= 0)
                    break;
                r[3] = a[3];
                if (--dl <= 0)
                    break;

                a += 4;
                r += 4;
            }
        }
    }
    return c;
}
#endif

#ifdef BN_RECURSION
/*
 * Karatsuba recursive multiplication algorithm (cf. Knuth, The Art of
 * Computer Programming, Vol. 2)
 */

/*-
 * r is 2*n2 words in size,
 * a and b are both n2 words in size.
 * n2 must be a power of 2.
 * We multiply and return the result.
 * t must be 2*n2 words in size
 * We calculate
 * a[0]*b[0]
 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
 * a[1]*b[1]
 */
/* dnX may not be positive, but n2/2+dnX has to be */
void bn_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,
                      int dna, int dnb, BN_ULONG *t)
{
    int n = n2 / 2, c1, c2;
    int tna = n + dna, tnb = n + dnb;
    unsigned int neg, zero;
    BN_ULONG ln, lo, *p;

# ifdef BN_MUL_COMBA
#  if 0
    if (n2 == 4) {
        bn_mul_comba4(r, a, b);
        return;
    }
#  endif
    /*
     * Only call bn_mul_comba 8 if n2 == 8 and the two arrays are complete
     * [steve]
     */
    if (n2 == 8 && dna == 0 && dnb == 0) {
        bn_mul_comba8(r, a, b);
        return;
    }
# endif                         /* BN_MUL_COMBA */
    /* Else do normal multiply */
    if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL) {
        bn_mul_normal(r, a, n2 + dna, b, n2 + dnb);
        if ((dna + dnb) < 0)
            memset(&r[2 * n2 + dna + dnb], 0,
                   sizeof(BN_ULONG) * -(dna + dnb));
        return;
    }
    /* r=(a[0]-a[1])*(b[1]-b[0]) */
    c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
    c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
    zero = neg = 0;
    switch (c1 * 3 + c2) {
    case -4:
        bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
        bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
        break;
    case -3:
        zero = 1;
        break;
    case -2:
        bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
        bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
        neg = 1;
        break;
    case -1:
    case 0:
    case 1:
        zero = 1;
        break;
    case 2:
        bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
        bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
        neg = 1;
        break;
    case 3:
        zero = 1;
        break;
    case 4:
        bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
        bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
        break;
    }

# ifdef BN_MUL_COMBA
    if (n == 4 && dna == 0 && dnb == 0) { /* XXX: bn_mul_comba4 could take
                                           * extra args to do this well */
        if (!zero)
            bn_mul_comba4(&(t[n2]), t, &(t[n]));
        else
            memset(&t[n2], 0, sizeof(*t) * 8);

        bn_mul_comba4(r, a, b);
        bn_mul_comba4(&(r[n2]), &(a[n]), &(b[n]));
    } else if (n == 8 && dna == 0 && dnb == 0) { /* XXX: bn_mul_comba8 could
                                                  * take extra args to do
                                                  * this well */
        if (!zero)
            bn_mul_comba8(&(t[n2]), t, &(t[n]));
        else
            memset(&t[n2], 0, sizeof(*t) * 16);

        bn_mul_comba8(r, a, b);
        bn_mul_comba8(&(r[n2]), &(a[n]), &(b[n]));
    } else
# endif                         /* BN_MUL_COMBA */
    {
        p = &(t[n2 * 2]);
        if (!zero)
            bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
        else
            memset(&t[n2], 0, sizeof(*t) * n2);
        bn_mul_recursive(r, a, b, n, 0, 0, p);
        bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]), n, dna, dnb, p);
    }

    /*-
     * t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
     * r[10] holds (a[0]*b[0])
     * r[32] holds (b[1]*b[1])
     */

    c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));

    if (neg) {                  /* if t[32] is negative */
        c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
    } else {
        /* Might have a carry */
        c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
    }

    /*-
     * t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
     * r[10] holds (a[0]*b[0])
     * r[32] holds (b[1]*b[1])
     * c1 holds the carry bits
     */
    c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
    if (c1) {
        p = &(r[n + n2]);
        lo = *p;
        ln = (lo + c1) & BN_MASK2;
        *p = ln;

        /*
         * The overflow will stop before we over write words we should not
         * overwrite
         */
        if (ln < (BN_ULONG)c1) {
            do {
                p++;
                lo = *p;
                ln = (lo + 1) & BN_MASK2;
                *p = ln;
            } while (ln == 0);
        }
    }
}

/*
 * n+tn is the word length t needs to be n*4 is size, as does r
 */
/* tnX may not be negative but less than n */
void bn_mul_part_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n,
                           int tna, int tnb, BN_ULONG *t)
{
    int i, j, n2 = n * 2;
    int c1, c2, neg;
    BN_ULONG ln, lo, *p;

    if (n < 8) {
        bn_mul_normal(r, a, n + tna, b, n + tnb);
        return;
    }

    /* r=(a[0]-a[1])*(b[1]-b[0]) */
    c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
    c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
    neg = 0;
    switch (c1 * 3 + c2) {
    case -4:
        bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
        bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
        break;
    case -3:
    case -2:
        bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
        bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
        neg = 1;
        break;
    case -1:
    case 0:
    case 1:
    case 2:
        bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
        bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
        neg = 1;
        break;
    case 3:
    case 4:
        bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
        bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
        break;
    }
    /*
     * The zero case isn't yet implemented here. The speedup would probably
     * be negligible.
     */
# if 0
    if (n == 4) {
        bn_mul_comba4(&(t[n2]), t, &(t[n]));
        bn_mul_comba4(r, a, b);
        bn_mul_normal(&(r[n2]), &(a[n]), tn, &(b[n]), tn);
        memset(&r[n2 + tn * 2], 0, sizeof(*r) * (n2 - tn * 2));
    } else
# endif
    if (n == 8) {
        bn_mul_comba8(&(t[n2]), t, &(t[n]));
        bn_mul_comba8(r, a, b);
        bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
        memset(&r[n2 + tna + tnb], 0, sizeof(*r) * (n2 - tna - tnb));
    } else {
        p = &(t[n2 * 2]);
        bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
        bn_mul_recursive(r, a, b, n, 0, 0, p);
        i = n / 2;
        /*
         * If there is only a bottom half to the number, just do it
         */
        if (tna > tnb)
            j = tna - i;
        else
            j = tnb - i;
        if (j == 0) {
            bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]),
                             i, tna - i, tnb - i, p);
            memset(&r[n2 + i * 2], 0, sizeof(*r) * (n2 - i * 2));
        } else if (j > 0) {     /* eg, n == 16, i == 8 and tn == 11 */
            bn_mul_part_recursive(&(r[n2]), &(a[n]), &(b[n]),
                                  i, tna - i, tnb - i, p);
            memset(&(r[n2 + tna + tnb]), 0,
                   sizeof(BN_ULONG) * (n2 - tna - tnb));
        } else {                /* (j < 0) eg, n == 16, i == 8 and tn == 5 */

            memset(&r[n2], 0, sizeof(*r) * n2);
            if (tna < BN_MUL_RECURSIVE_SIZE_NORMAL
                && tnb < BN_MUL_RECURSIVE_SIZE_NORMAL) {
                bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
            } else {
                for (;;) {
                    i /= 2;
                    /*
                     * these simplified conditions work exclusively because
                     * difference between tna and tnb is 1 or 0
                     */
                    if (i < tna || i < tnb) {
                        bn_mul_part_recursive(&(r[n2]),
                                              &(a[n]), &(b[n]),
                                              i, tna - i, tnb - i, p);
                        break;
                    } else if (i == tna || i == tnb) {
                        bn_mul_recursive(&(r[n2]),
                                         &(a[n]), &(b[n]),
                                         i, tna - i, tnb - i, p);
                        break;
                    }
                }
            }
        }
    }

    /*-
     * t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
     * r[10] holds (a[0]*b[0])
     * r[32] holds (b[1]*b[1])
     */

    c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));

    if (neg) {                  /* if t[32] is negative */
        c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
    } else {
        /* Might have a carry */
        c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
    }

    /*-
     * t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
     * r[10] holds (a[0]*b[0])
     * r[32] holds (b[1]*b[1])
     * c1 holds the carry bits
     */
    c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
    if (c1) {
        p = &(r[n + n2]);
        lo = *p;
        ln = (lo + c1) & BN_MASK2;
        *p = ln;

        /*
         * The overflow will stop before we over write words we should not
         * overwrite
         */
        if (ln < (BN_ULONG)c1) {
            do {
                p++;
                lo = *p;
                ln = (lo + 1) & BN_MASK2;
                *p = ln;
            } while (ln == 0);
        }
    }
}

/*-
 * a and b must be the same size, which is n2.
 * r needs to be n2 words and t needs to be n2*2
 */
void bn_mul_low_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,
                          BN_ULONG *t)
{
    int n = n2 / 2;

    bn_mul_recursive(r, a, b, n, 0, 0, &(t[0]));
    if (n >= BN_MUL_LOW_RECURSIVE_SIZE_NORMAL) {
        bn_mul_low_recursive(&(t[0]), &(a[0]), &(b[n]), n, &(t[n2]));
        bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
        bn_mul_low_recursive(&(t[0]), &(a[n]), &(b[0]), n, &(t[n2]));
        bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
    } else {
        bn_mul_low_normal(&(t[0]), &(a[0]), &(b[n]), n);
        bn_mul_low_normal(&(t[n]), &(a[n]), &(b[0]), n);
        bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
        bn_add_words(&(r[n]), &(r[n]), &(t[n]), n);
    }
}
#endif                          /* BN_RECURSION */

int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
{
    int ret = bn_mul_fixed_top(r, a, b, ctx);

    bn_correct_top(r);
    bn_check_top(r);

    return ret;
}

int bn_mul_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
{
    int ret = 0;
    int top, al, bl;
    BIGNUM *rr;
#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
    int i;
#endif
#ifdef BN_RECURSION
    BIGNUM *t = NULL;
    int j = 0, k;
#endif

    bn_check_top(a);
    bn_check_top(b);
    bn_check_top(r);

    al = a->top;
    bl = b->top;

    if ((al == 0) || (bl == 0)) {
        BN_zero(r);
        return 1;
    }
    top = al + bl;

    BN_CTX_start(ctx);
    if ((r == a) || (r == b)) {
        if ((rr = BN_CTX_get(ctx)) == NULL)
            goto err;
    } else
        rr = r;

#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
    i = al - bl;
#endif
#ifdef BN_MUL_COMBA
    if (i == 0) {
# if 0
        if (al == 4) {
            if (bn_wexpand(rr, 8) == NULL)
                goto err;
            rr->top = 8;
            bn_mul_comba4(rr->d, a->d, b->d);
            goto end;
        }
# endif
        if (al == 8) {
            if (bn_wexpand(rr, 16) == NULL)
                goto err;
            rr->top = 16;
            bn_mul_comba8(rr->d, a->d, b->d);
            goto end;
        }
    }
#endif                          /* BN_MUL_COMBA */
#ifdef BN_RECURSION
    if ((al >= BN_MULL_SIZE_NORMAL) && (bl >= BN_MULL_SIZE_NORMAL)) {
        if (i >= -1 && i <= 1) {
            /*
             * Find out the power of two lower or equal to the longest of the
             * two numbers
             */
            if (i >= 0) {
                j = BN_num_bits_word((BN_ULONG)al);
            }
            if (i == -1) {
                j = BN_num_bits_word((BN_ULONG)bl);
            }
            j = 1 << (j - 1);
            assert(j <= al || j <= bl);
            k = j + j;
            t = BN_CTX_get(ctx);
            if (t == NULL)
                goto err;
            if (al > j || bl > j) {
                if (bn_wexpand(t, k * 4) == NULL)
                    goto err;
                if (bn_wexpand(rr, k * 4) == NULL)
                    goto err;
                bn_mul_part_recursive(rr->d, a->d, b->d,
                                      j, al - j, bl - j, t->d);
            } else {            /* al <= j || bl <= j */

                if (bn_wexpand(t, k * 2) == NULL)
                    goto err;
                if (bn_wexpand(rr, k * 2) == NULL)
                    goto err;
                bn_mul_recursive(rr->d, a->d, b->d, j, al - j, bl - j, t->d);
            }
            rr->top = top;
            goto end;
        }
    }
#endif                          /* BN_RECURSION */
    if (bn_wexpand(rr, top) == NULL)
        goto err;
    rr->top = top;
    bn_mul_normal(rr->d, a->d, al, b->d, bl);

#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
 end:
#endif
    rr->neg = a->neg ^ b->neg;
    rr->flags |= BN_FLG_FIXED_TOP;
    if (r != rr && BN_copy(r, rr) == NULL)
        goto err;

    ret = 1;
 err:
    bn_check_top(r);
    BN_CTX_end(ctx);
    return ret;
}

void bn_mul_normal(BN_ULONG *r, BN_ULONG *a, int na, BN_ULONG *b, int nb)
{
    BN_ULONG *rr;

    if (na < nb) {
        int itmp;
        BN_ULONG *ltmp;

        itmp = na;
        na = nb;
        nb = itmp;
        ltmp = a;
        a = b;
        b = ltmp;

    }
    rr = &(r[na]);
    if (nb <= 0) {
        (void)bn_mul_words(r, a, na, 0);
        return;
    } else
        rr[0] = bn_mul_words(r, a, na, b[0]);

    for (;;) {
        if (--nb <= 0)
            return;
        rr[1] = bn_mul_add_words(&(r[1]), a, na, b[1]);
        if (--nb <= 0)
            return;
        rr[2] = bn_mul_add_words(&(r[2]), a, na, b[2]);
        if (--nb <= 0)
            return;
        rr[3] = bn_mul_add_words(&(r[3]), a, na, b[3]);
        if (--nb <= 0)
            return;
        rr[4] = bn_mul_add_words(&(r[4]), a, na, b[4]);
        rr += 4;
        r += 4;
        b += 4;
    }
}

void bn_mul_low_normal(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n)
{
    bn_mul_words(r, a, n, b[0]);

    for (;;) {
        if (--n <= 0)
            return;
        bn_mul_add_words(&(r[1]), a, n, b[1]);
        if (--n <= 0)
            return;
        bn_mul_add_words(&(r[2]), a, n, b[2]);
        if (--n <= 0)
            return;
        bn_mul_add_words(&(r[3]), a, n, b[3]);
        if (--n <= 0)
            return;
        bn_mul_add_words(&(r[4]), a, n, b[4]);
        r += 4;
        b += 4;
    }
}

Coverage Report

Created: 2023-06-08 06:41

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
3		*
4		* Licensed under the OpenSSL license (the "License"). You may not use
5		* this file except in compliance with the License. You can obtain a copy
6		* in the file LICENSE in the source distribution or at
7		* https://www.openssl.org/source/license.html
8		*/
9
10		#include <assert.h>
11		#include "internal/cryptlib.h"
12		#include "bn_local.h"
13
14		#if defined(OPENSSL_NO_ASM) \|\| !defined(OPENSSL_BN_ASM_PART_WORDS)
15		/*
16		* Here follows specialised variants of bn_add_words() and bn_sub_words().
17		* They have the property performing operations on arrays of different sizes.
18		* The sizes of those arrays is expressed through cl, which is the common
19		* length ( basically, min(len(a),len(b)) ), and dl, which is the delta
20		* between the two lengths, calculated as len(a)-len(b). All lengths are the
21		* number of BN_ULONGs... For the operations that require a result array as
22		* parameter, it must have the length cl+abs(dl). These functions should
23		* probably end up in bn_asm.c as soon as there are assembler counterparts
24		* for the systems that use assembler files.
25		*/
26
27		BN_ULONG bn_sub_part_words(BN_ULONG *r,
28		const BN_ULONG a, const BN_ULONG b,
29		int cl, int dl)
30	58.9k	{
31	58.9k	BN_ULONG c, t;
32
33	58.9k	assert(cl >= 0);
34	58.9k	c = bn_sub_words(r, a, b, cl);
35
36	58.9k	if (dl == 0)
37	55.1k	return c;
38
39	3.76k	r += cl;
40	3.76k	a += cl;
41	3.76k	b += cl;
42
43	3.76k	if (dl < 0) {
44	418	for (;;) {
45	418	t = b[0];
46	418	r[0] = (0 - t - c) & BN_MASK2;
47	418	if (t != 0)
48	0	c = 1;
49	418	if (++dl >= 0)
50	166	break;
51
52	252	t = b[1];
53	252	r[1] = (0 - t - c) & BN_MASK2;
54	252	if (t != 0)
55	0	c = 1;
56	252	if (++dl >= 0)
57	58	break;
58
59	194	t = b[2];
60	194	r[2] = (0 - t - c) & BN_MASK2;
61	194	if (t != 0)
62	0	c = 1;
63	194	if (++dl >= 0)
64	34	break;
65
66	160	t = b[3];
67	160	r[3] = (0 - t - c) & BN_MASK2;
68	160	if (t != 0)
69	0	c = 1;
70	160	if (++dl >= 0)
71	24	break;
72
73	136	b += 4;
74	136	r += 4;
75	136	}
76	3.48k	} else {
77	3.48k	int save_dl = dl;
78	4.38k	while (c) {
79	1.33k	t = a[0];
80	1.33k	r[0] = (t - c) & BN_MASK2;
81	1.33k	if (t != 0)
82	886	c = 0;
83	1.33k	if (--dl <= 0)
84	194	break;
85
86	1.13k	t = a[1];
87	1.13k	r[1] = (t - c) & BN_MASK2;
88	1.13k	if (t != 0)
89	744	c = 0;
90	1.13k	if (--dl <= 0)
91	106	break;
92
93	1.03k	t = a[2];
94	1.03k	r[2] = (t - c) & BN_MASK2;
95	1.03k	if (t != 0)
96	650	c = 0;
97	1.03k	if (--dl <= 0)
98	88	break;
99
100	942	t = a[3];
101	942	r[3] = (t - c) & BN_MASK2;
102	942	if (t != 0)
103	568	c = 0;
104	942	if (--dl <= 0)
105	48	break;
106
107	894	save_dl = dl;
108	894	a += 4;
109	894	r += 4;
110	894	}
111	3.48k	if (dl > 0) {
112	3.05k	if (save_dl > dl) {
113	0	switch (save_dl - dl) {
114	0	case 1:
115	0	r[1] = a[1];
116	0	if (--dl <= 0)
117	0	break;
118		/* fall thru */
119	0	case 2:
120	0	r[2] = a[2];
121	0	if (--dl <= 0)
122	0	break;
123		/* fall thru */
124	0	case 3:
125	0	r[3] = a[3];
126	0	if (--dl <= 0)
127	0	break;
128	0	}
129	0	a += 4;
130	0	r += 4;
131	0	}
132	3.05k	}
133	3.48k	if (dl > 0) {
134	31.1k	for (;;) {
135	31.1k	r[0] = a[0];
136	31.1k	if (--dl <= 0)
137	726	break;
138	30.4k	r[1] = a[1];
139	30.4k	if (--dl <= 0)
140	94	break;
141	30.3k	r[2] = a[2];
142	30.3k	if (--dl <= 0)
143	1.16k	break;
144	29.1k	r[3] = a[3];
145	29.1k	if (--dl <= 0)
146	1.06k	break;
147
148	28.1k	a += 4;
149	28.1k	r += 4;
150	28.1k	}
151	3.05k	}
152	3.48k	}
153	3.76k	return c;
154	3.76k	}
155		#endif
156
157		#ifdef BN_RECURSION
158		/*
159		* Karatsuba recursive multiplication algorithm (cf. Knuth, The Art of
160		* Computer Programming, Vol. 2)
161		*/
162
163		/*-
164		* r is 2*n2 words in size,
165		* a and b are both n2 words in size.
166		* n2 must be a power of 2.
167		* We multiply and return the result.
168		* t must be 2*n2 words in size
169		* We calculate
170		* a[0]*b[0]
171		* a[0]b[0]+a[1]b[1]+(a[0]-a[1])*(b[1]-b[0])
172		* a[1]*b[1]
173		*/
174		/* dnX may not be positive, but n2/2+dnX has to be */
175		void bn_mul_recursive(BN_ULONG r, BN_ULONG a, BN_ULONG *b, int n2,
176		int dna, int dnb, BN_ULONG *t)
177	28.3k	{
178	28.3k	int n = n2 / 2, c1, c2;
179	28.3k	int tna = n + dna, tnb = n + dnb;
180	28.3k	unsigned int neg, zero;
181	28.3k	BN_ULONG ln, lo, *p;
182
183	28.3k	# ifdef BN_MUL_COMBA
184		# if 0
185		if (n2 == 4) {
186		bn_mul_comba4(r, a, b);
187		return;
188		}
189		# endif
190		/*
191		* Only call bn_mul_comba 8 if n2 == 8 and the two arrays are complete
192		* [steve]
193		*/
194	28.3k	if (n2 == 8 && dna == 0 && dnb == 0) {
195	50	bn_mul_comba8(r, a, b);
196	50	return;
197	50	}
198	28.3k	# endif /* BN_MUL_COMBA */
199		/* Else do normal multiply */
200	28.3k	if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL) {
201	26	bn_mul_normal(r, a, n2 + dna, b, n2 + dnb);
202	26	if ((dna + dnb) < 0)
203	26	memset(&r[2 * n2 + dna + dnb], 0,
204	26	sizeof(BN_ULONG) * -(dna + dnb));
205	26	return;
206	26	}
207		/* r=(a[0]-a[1])(b[1]-b[0]) /
208	28.3k	c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
209	28.3k	c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
210	28.3k	zero = neg = 0;
211	28.3k	switch (c1 * 3 + c2) {
212	7.12k	case -4:
213	7.12k	bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
214	7.12k	bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
215	7.12k	break;
216	170	case -3:
217	170	zero = 1;
218	170	break;
219	5.36k	case -2:
220	5.36k	bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
221	5.36k	bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
222	5.36k	neg = 1;
223	5.36k	break;
224	136	case -1:
225	276	case 0:
226	378	case 1:
227	378	zero = 1;
228	378	break;
229	8.77k	case 2:
230	8.77k	bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
231	8.77k	bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
232	8.77k	neg = 1;
233	8.77k	break;
234	140	case 3:
235	140	zero = 1;
236	140	break;
237	6.36k	case 4:
238	6.36k	bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
239	6.36k	bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
240	6.36k	break;
241	28.3k	}
242
243	28.3k	# ifdef BN_MUL_COMBA
244	28.3k	if (n == 4 && dna == 0 && dnb == 0) { /* XXX: bn_mul_comba4 could take
245		* extra args to do this well */
246	0	if (!zero)
247	0	bn_mul_comba4(&(t[n2]), t, &(t[n]));
248	0	else
249	0	memset(&t[n2], 0, sizeof(t) 8);
250
251	0	bn_mul_comba4(r, a, b);
252	0	bn_mul_comba4(&(r[n2]), &(a[n]), &(b[n]));
253	28.3k	} else if (n == 8 && dna == 0 && dnb == 0) { /* XXX: bn_mul_comba8 could
254		* take extra args to do
255		* this well */
256	19.9k	if (!zero)
257	19.3k	bn_mul_comba8(&(t[n2]), t, &(t[n]));
258	588	else
259	588	memset(&t[n2], 0, sizeof(t) 16);
260
261	19.9k	bn_mul_comba8(r, a, b);
262	19.9k	bn_mul_comba8(&(r[n2]), &(a[n]), &(b[n]));
263	19.9k	} else
264	8.41k	# endif /* BN_MUL_COMBA */
265	8.41k	{
266	8.41k	p = &(t[n2 * 2]);
267	8.41k	if (!zero)
268	8.31k	bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
269	100	else
270	100	memset(&t[n2], 0, sizeof(t) n2);
271	8.41k	bn_mul_recursive(r, a, b, n, 0, 0, p);
272	8.41k	bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]), n, dna, dnb, p);
273	8.41k	}
274
275		/*-
276		* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
277		* r[10] holds (a[0]*b[0])
278		* r[32] holds (b[1]*b[1])
279		*/
280
281	28.3k	c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
282
283	28.3k	if (neg) { /* if t[32] is negative */
284	14.1k	c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
285	14.1k	} else {
286		/* Might have a carry */
287	14.1k	c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
288	14.1k	}
289
290		/*-
291		* t[32] holds (a[0]-a[1])(b[1]-b[0])+(a[0]b[0])+(a[1]*b[1])
292		* r[10] holds (a[0]*b[0])
293		* r[32] holds (b[1]*b[1])
294		* c1 holds the carry bits
295		*/
296	28.3k	c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
297	28.3k	if (c1) {
298	10.1k	p = &(r[n + n2]);
299	10.1k	lo = *p;
300	10.1k	ln = (lo + c1) & BN_MASK2;
301	10.1k	*p = ln;
302
303		/*
304		* The overflow will stop before we over write words we should not
305		* overwrite
306		*/
307	10.1k	if (ln < (BN_ULONG)c1) {
308	678	do {
309	678	p++;
310	678	lo = *p;
311	678	ln = (lo + 1) & BN_MASK2;
312	678	*p = ln;
313	678	} while (ln == 0);
314	198	}
315	10.1k	}
316	28.3k	}
317
318		/*
319		* n+tn is the word length t needs to be n*4 is size, as does r
320		*/
321		/* tnX may not be negative but less than n */
322		void bn_mul_part_recursive(BN_ULONG r, BN_ULONG a, BN_ULONG *b, int n,
323		int tna, int tnb, BN_ULONG *t)
324	1.84k	{
325	1.84k	int i, j, n2 = n * 2;
326	1.84k	int c1, c2, neg;
327	1.84k	BN_ULONG ln, lo, *p;
328
329	1.84k	if (n < 8) {
330	0	bn_mul_normal(r, a, n + tna, b, n + tnb);
331	0	return;
332	0	}
333
334		/* r=(a[0]-a[1])(b[1]-b[0]) /
335	1.84k	c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
336	1.84k	c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
337	1.84k	neg = 0;
338	1.84k	switch (c1 * 3 + c2) {
339	178	case -4:
340	178	bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
341	178	bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
342	178	break;
343	2	case -3:
344	26	case -2:
345	26	bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
346	26	bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
347	26	neg = 1;
348	26	break;
349	2	case -1:
350	4	case 0:
351	6	case 1:
352	1.59k	case 2:
353	1.59k	bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
354	1.59k	bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
355	1.59k	neg = 1;
356	1.59k	break;
357	2	case 3:
358	50	case 4:
359	50	bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
360	50	bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
361	50	break;
362	1.84k	}
363		/*
364		* The zero case isn't yet implemented here. The speedup would probably
365		* be negligible.
366		*/
367		# if 0
368		if (n == 4) {
369		bn_mul_comba4(&(t[n2]), t, &(t[n]));
370		bn_mul_comba4(r, a, b);
371		bn_mul_normal(&(r[n2]), &(a[n]), tn, &(b[n]), tn);
372		memset(&r[n2 + tn * 2], 0, sizeof(r) (n2 - tn * 2));
373		} else
374		# endif
375	1.84k	if (n == 8) {
376	260	bn_mul_comba8(&(t[n2]), t, &(t[n]));
377	260	bn_mul_comba8(r, a, b);
378	260	bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
379	260	memset(&r[n2 + tna + tnb], 0, sizeof(r) (n2 - tna - tnb));
380	1.58k	} else {
381	1.58k	p = &(t[n2 * 2]);
382	1.58k	bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
383	1.58k	bn_mul_recursive(r, a, b, n, 0, 0, p);
384	1.58k	i = n / 2;
385		/*
386		* If there is only a bottom half to the number, just do it
387		*/
388	1.58k	if (tna > tnb)
389	1.08k	j = tna - i;
390	502	else
391	502	j = tnb - i;
392	1.58k	if (j == 0) {
393	4	bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]),
394	4	i, tna - i, tnb - i, p);
395	4	memset(&r[n2 + i * 2], 0, sizeof(r) (n2 - i * 2));
396	1.58k	} else if (j > 0) { /* eg, n == 16, i == 8 and tn == 11 */
397	528	bn_mul_part_recursive(&(r[n2]), &(a[n]), &(b[n]),
398	528	i, tna - i, tnb - i, p);
399	528	memset(&(r[n2 + tna + tnb]), 0,
400	528	sizeof(BN_ULONG) * (n2 - tna - tnb));
401	1.05k	} else { /* (j < 0) eg, n == 16, i == 8 and tn == 5 */
402
403	1.05k	memset(&r[n2], 0, sizeof(r) n2);
404	1.05k	if (tna < BN_MUL_RECURSIVE_SIZE_NORMAL
405	1.05k	&& tnb < BN_MUL_RECURSIVE_SIZE_NORMAL) {
406	1.05k	bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
407	1.05k	} else {
408	0	for (;;) {
409	0	i /= 2;
410		/*
411		* these simplified conditions work exclusively because
412		* difference between tna and tnb is 1 or 0
413		*/
414	0	if (i < tna \|\| i < tnb) {
415	0	bn_mul_part_recursive(&(r[n2]),
416	0	&(a[n]), &(b[n]),
417	0	i, tna - i, tnb - i, p);
418	0	break;
419	0	} else if (i == tna \|\| i == tnb) {
420	0	bn_mul_recursive(&(r[n2]),
421	0	&(a[n]), &(b[n]),
422	0	i, tna - i, tnb - i, p);
423	0	break;
424	0	}
425	0	}
426	0	}
427	1.05k	}
428	1.58k	}
429
430		/*-
431		* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
432		* r[10] holds (a[0]*b[0])
433		* r[32] holds (b[1]*b[1])
434		*/
435
436	1.84k	c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
437
438	1.84k	if (neg) { /* if t[32] is negative */
439	1.62k	c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
440	1.62k	} else {
441		/* Might have a carry */
442	228	c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
443	228	}
444
445		/*-
446		* t[32] holds (a[0]-a[1])(b[1]-b[0])+(a[0]b[0])+(a[1]*b[1])
447		* r[10] holds (a[0]*b[0])
448		* r[32] holds (b[1]*b[1])
449		* c1 holds the carry bits
450		*/
451	1.84k	c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
452	1.84k	if (c1) {
453	142	p = &(r[n + n2]);
454	142	lo = *p;
455	142	ln = (lo + c1) & BN_MASK2;
456	142	*p = ln;
457
458		/*
459		* The overflow will stop before we over write words we should not
460		* overwrite
461		*/
462	142	if (ln < (BN_ULONG)c1) {
463	54	do {
464	54	p++;
465	54	lo = *p;
466	54	ln = (lo + 1) & BN_MASK2;
467	54	*p = ln;
468	54	} while (ln == 0);
469	18	}
470	142	}
471	1.84k	}
472
473		/*-
474		* a and b must be the same size, which is n2.
475		* r needs to be n2 words and t needs to be n2*2
476		*/
477		void bn_mul_low_recursive(BN_ULONG r, BN_ULONG a, BN_ULONG *b, int n2,
478		BN_ULONG *t)
479	0	{
480	0	int n = n2 / 2;
481
482	0	bn_mul_recursive(r, a, b, n, 0, 0, &(t[0]));
483	0	if (n >= BN_MUL_LOW_RECURSIVE_SIZE_NORMAL) {
484	0	bn_mul_low_recursive(&(t[0]), &(a[0]), &(b[n]), n, &(t[n2]));
485	0	bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
486	0	bn_mul_low_recursive(&(t[0]), &(a[n]), &(b[0]), n, &(t[n2]));
487	0	bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
488	0	} else {
489	0	bn_mul_low_normal(&(t[0]), &(a[0]), &(b[n]), n);
490	0	bn_mul_low_normal(&(t[n]), &(a[n]), &(b[0]), n);
491	0	bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
492	0	bn_add_words(&(r[n]), &(r[n]), &(t[n]), n);
493	0	}
494	0	}
495		#endif /* BN_RECURSION */
496
497		int BN_mul(BIGNUM r, const BIGNUM a, const BIGNUM b, BN_CTX ctx)
498	180k	{
499	180k	int ret = bn_mul_fixed_top(r, a, b, ctx);
500
501	180k	bn_correct_top(r);
502	180k	bn_check_top(r);
503
504	180k	return ret;
505	180k	}
506
507		int bn_mul_fixed_top(BIGNUM r, const BIGNUM a, const BIGNUM b, BN_CTX ctx)
508	288k	{
509	288k	int ret = 0;
510	288k	int top, al, bl;
511	288k	BIGNUM *rr;
512	288k	#if defined(BN_MUL_COMBA) \|\| defined(BN_RECURSION)
513	288k	int i;
514	288k	#endif
515	288k	#ifdef BN_RECURSION
516	288k	BIGNUM *t = NULL;
517	288k	int j = 0, k;
518	288k	#endif
519
520	288k	bn_check_top(a);
521	288k	bn_check_top(b);
522	288k	bn_check_top(r);
523
524	288k	al = a->top;
525	288k	bl = b->top;
526
527	288k	if ((al == 0) \|\| (bl == 0)) {
528	38.2k	BN_zero(r);
529	38.2k	return 1;
530	38.2k	}
531	250k	top = al + bl;
532
533	250k	BN_CTX_start(ctx);
534	250k	if ((r == a) \|\| (r == b)) {
535	5.49k	if ((rr = BN_CTX_get(ctx)) == NULL)
536	0	goto err;
537	5.49k	} else
538	244k	rr = r;
539
540	250k	#if defined(BN_MUL_COMBA) \|\| defined(BN_RECURSION)
541	250k	i = al - bl;
542	250k	#endif
543	250k	#ifdef BN_MUL_COMBA
544	250k	if (i == 0) {
545		# if 0
546		if (al == 4) {
547		if (bn_wexpand(rr, 8) == NULL)
548		goto err;
549		rr->top = 8;
550		bn_mul_comba4(rr->d, a->d, b->d);
551		goto end;
552		}
553		# endif
554	162k	if (al == 8) {
555	210	if (bn_wexpand(rr, 16) == NULL)
556	0	goto err;
557	210	rr->top = 16;
558	210	bn_mul_comba8(rr->d, a->d, b->d);
559	210	goto end;
560	210	}
561	162k	}
562	249k	#endif /* BN_MUL_COMBA */
563	249k	#ifdef BN_RECURSION
564	249k	if ((al >= BN_MULL_SIZE_NORMAL) && (bl >= BN_MULL_SIZE_NORMAL)) {
565	2.77k	if (i >= -1 && i <= 1) {
566		/*
567		* Find out the power of two lower or equal to the longest of the
568		* two numbers
569		*/
570	1.38k	if (i >= 0) {
571	1.29k	j = BN_num_bits_word((BN_ULONG)al);
572	1.29k	}
573	1.38k	if (i == -1) {
574	90	j = BN_num_bits_word((BN_ULONG)bl);
575	90	}
576	1.38k	j = 1 << (j - 1);
577	1.38k	assert(j <= al \|\| j <= bl);
578	1.38k	k = j + j;
579	1.38k	t = BN_CTX_get(ctx);
580	1.38k	if (t == NULL)
581	0	goto err;
582	1.38k	if (al > j \|\| bl > j) {
583	1.32k	if (bn_wexpand(t, k * 4) == NULL)
584	0	goto err;
585	1.32k	if (bn_wexpand(rr, k * 4) == NULL)
586	0	goto err;
587	1.32k	bn_mul_part_recursive(rr->d, a->d, b->d,
588	1.32k	j, al - j, bl - j, t->d);
589	1.32k	} else { /* al <= j \|\| bl <= j */
590
591	62	if (bn_wexpand(t, k * 2) == NULL)
592	0	goto err;
593	62	if (bn_wexpand(rr, k * 2) == NULL)
594	0	goto err;
595	62	bn_mul_recursive(rr->d, a->d, b->d, j, al - j, bl - j, t->d);
596	62	}
597	1.38k	rr->top = top;
598	1.38k	goto end;
599	1.38k	}
600	2.77k	}
601	248k	#endif /* BN_RECURSION */
602	248k	if (bn_wexpand(rr, top) == NULL)
603	0	goto err;
604	248k	rr->top = top;
605	248k	bn_mul_normal(rr->d, a->d, al, b->d, bl);
606
607	248k	#if defined(BN_MUL_COMBA) \|\| defined(BN_RECURSION)
608	250k	end:
609	250k	#endif
610	250k	rr->neg = a->neg ^ b->neg;
611	250k	rr->flags \|= BN_FLG_FIXED_TOP;
612	250k	if (r != rr && BN_copy(r, rr) == NULL)
613	0	goto err;
614
615	250k	ret = 1;
616	250k	err:
617	250k	bn_check_top(r);
618	250k	BN_CTX_end(ctx);
619	250k	return ret;
620	250k	}
621
622		void bn_mul_normal(BN_ULONG r, BN_ULONG a, int na, BN_ULONG *b, int nb)
623	249k	{
624	249k	BN_ULONG *rr;
625
626	249k	if (na < nb) {
627	56.6k	int itmp;
628	56.6k	BN_ULONG *ltmp;
629
630	56.6k	itmp = na;
631	56.6k	na = nb;
632	56.6k	nb = itmp;
633	56.6k	ltmp = a;
634	56.6k	a = b;
635	56.6k	b = ltmp;
636
637	56.6k	}
638	249k	rr = &(r[na]);
639	249k	if (nb <= 0) {
640	988	(void)bn_mul_words(r, a, na, 0);
641	988	return;
642	988	} else
643	248k	rr[0] = bn_mul_words(r, a, na, b[0]);
644
645	274k	for (;;) {
646	274k	if (--nb <= 0)
647	73.9k	return;
648	201k	rr[1] = bn_mul_add_words(&(r[1]), a, na, b[1]);
649	201k	if (--nb <= 0)
650	16.5k	return;
651	184k	rr[2] = bn_mul_add_words(&(r[2]), a, na, b[2]);
652	184k	if (--nb <= 0)
653	1.56k	return;
654	182k	rr[3] = bn_mul_add_words(&(r[3]), a, na, b[3]);
655	182k	if (--nb <= 0)
656	156k	return;
657	26.0k	rr[4] = bn_mul_add_words(&(r[4]), a, na, b[4]);
658	26.0k	rr += 4;
659	26.0k	r += 4;
660	26.0k	b += 4;
661	26.0k	}
662	248k	}
663
664		void bn_mul_low_normal(BN_ULONG r, BN_ULONG a, BN_ULONG *b, int n)
665	0	{
666	0	bn_mul_words(r, a, n, b[0]);
667
668	0	for (;;) {
669	0	if (--n <= 0)
670	0	return;
671	0	bn_mul_add_words(&(r[1]), a, n, b[1]);
672	0	if (--n <= 0)
673	0	return;
674	0	bn_mul_add_words(&(r[2]), a, n, b[2]);
675	0	if (--n <= 0)
676	0	return;
677	0	bn_mul_add_words(&(r[3]), a, n, b[3]);
678	0	if (--n <= 0)
679	0	return;
680	0	bn_mul_add_words(&(r[4]), a, n, b[4]);
681	0	r += 4;
682	0	b += 4;
683	0	}
684	0	}