-typedef unsigned short *Bignum;
-
-static unsigned short Zero[1] = { 0 };
-
-#if defined TESTMODE || defined RSADEBUG
-#ifndef DLVL
-#define DLVL 10000
-#endif
-#define debug(x) bndebug(#x,x)
-static int level = 0;
-static void bndebug(char *name, Bignum b) {
- int i;
- int w = 50-level-strlen(name)-5*b[0];
- if (level >= DLVL)
- return;
- if (w < 0) w = 0;
- dprintf("%*s%s%*s", level, "", name, w, "");
- for (i=b[0]; i>0; i--)
- dprintf(" %04x", b[i]);
- dprintf("\n");
-}
-#define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0)
-#define enter(x) do { dmsg(x); level += 4; } while(0)
-#define leave(x) do { level -= 4; dmsg(x); } while(0)
-#else
-#define debug(x)
-#define dmsg(x)
-#define enter(x)
-#define leave(x)
-#endif
-
-static Bignum newbn(int length) {
- Bignum b = malloc((length+1)*sizeof(unsigned short));
- if (!b)
- abort(); /* FIXME */
- b[0] = length;
- return b;
-}
-
-static void freebn(Bignum b) {
- free(b);
-}
-
-/*
- * Compute c = a * b.
- * Input is in the first len words of a and b.
- * Result is returned in the first 2*len words of c.
- */
-static void bigmul(unsigned short *a, unsigned short *b, unsigned short *c,
- int len)
-{
- int i, j;
- unsigned long ai, t;
-
- for (j = len - 1; j >= 0; j--)
- c[j+len] = 0;
-
- for (i = len - 1; i >= 0; i--) {
- ai = a[i];
- t = 0;
- for (j = len - 1; j >= 0; j--) {
- t += ai * (unsigned long) b[j];
- t += (unsigned long) c[i+j+1];
- c[i+j+1] = (unsigned short)t;
- t = t >> 16;
- }
- c[i] = (unsigned short)t;
- }
-}
-
-/*
- * Compute a = a % m.
- * Input in first 2*len words of a and first len words of m.
- * Output in first 2*len words of a (of which first len words will be zero).
- * The MSW of m MUST have its high bit set.
- */
-static void bigmod(unsigned short *a, unsigned short *m, int len)
-{
- unsigned short m0, m1;
- unsigned int h;
- int i, k;
-
- /* Special case for len == 1 */
- if (len == 1) {
- a[1] = (((long) a[0] << 16) + a[1]) % m[0];
- a[0] = 0;
- return;
- }
-
- m0 = m[0];
- m1 = m[1];
-
- for (i = 0; i <= len; i++) {
- unsigned long t;
- unsigned int q, r, c;
-
- if (i == 0) {
- h = 0;
- } else {
- h = a[i-1];
- a[i-1] = 0;
- }
-
- /* Find q = h:a[i] / m0 */
- t = ((unsigned long) h << 16) + a[i];
- q = t / m0;
- r = t % m0;
-
- /* Refine our estimate of q by looking at
- h:a[i]:a[i+1] / m0:m1 */
- t = (long) m1 * (long) q;
- if (t > ((unsigned long) r << 16) + a[i+1]) {
- q--;
- t -= m1;
- r = (r + m0) & 0xffff; /* overflow? */
- if (r >= m0 && t > ((unsigned long) r << 16) + a[i+1])
- q--;
- }
-
- /* Substract q * m from a[i...] */
- c = 0;
- for (k = len - 1; k >= 0; k--) {
- t = (long) q * (long) m[k];
- t += c;
- c = t >> 16;
- if ((unsigned short) t > a[i+k]) c++;
- a[i+k] -= (unsigned short) t;
- }
-
- /* Add back m in case of borrow */
- if (c != h) {
- t = 0;
- for (k = len - 1; k >= 0; k--) {
- t += m[k];
- t += a[i+k];
- a[i+k] = (unsigned short)t;
- t = t >> 16;
- }
- }
- }
-}
-
-/*
- * Compute (base ^ exp) % mod.
- * The base MUST be smaller than the modulus.
- * The most significant word of mod MUST be non-zero.
- * We assume that the result array is the same size as the mod array.
- */
-static void modpow(Bignum base, Bignum exp, Bignum mod, Bignum result)
-{
- unsigned short *a, *b, *n, *m;
- int mshift;
- int mlen, i, j;
-
- /* Allocate m of size mlen, copy mod to m */
- /* We use big endian internally */
- mlen = mod[0];
- m = malloc(mlen * sizeof(unsigned short));
- for (j = 0; j < mlen; j++) m[j] = mod[mod[0] - j];
-
- /* Shift m left to make msb bit set */
- for (mshift = 0; mshift < 15; mshift++)
- if ((m[0] << mshift) & 0x8000) break;
- if (mshift) {
- for (i = 0; i < mlen - 1; i++)
- m[i] = (m[i] << mshift) | (m[i+1] >> (16-mshift));
- m[mlen-1] = m[mlen-1] << mshift;
- }
-
- /* Allocate n of size mlen, copy base to n */
- n = malloc(mlen * sizeof(unsigned short));
- i = mlen - base[0];
- for (j = 0; j < i; j++) n[j] = 0;
- for (j = 0; j < base[0]; j++) n[i+j] = base[base[0] - j];
-
- /* Allocate a and b of size 2*mlen. Set a = 1 */
- a = malloc(2 * mlen * sizeof(unsigned short));
- b = malloc(2 * mlen * sizeof(unsigned short));
- for (i = 0; i < 2*mlen; i++) a[i] = 0;
- a[2*mlen-1] = 1;
-
- /* Skip leading zero bits of exp. */
- i = 0; j = 15;
- while (i < exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) {
- j--;
- if (j < 0) { i++; j = 15; }
- }
-
- /* Main computation */
- while (i < exp[0]) {
- while (j >= 0) {
- bigmul(a + mlen, a + mlen, b, mlen);
- bigmod(b, m, mlen);
- if ((exp[exp[0] - i] & (1 << j)) != 0) {
- bigmul(b + mlen, n, a, mlen);
- bigmod(a, m, mlen);
- } else {
- unsigned short *t;
- t = a; a = b; b = t;
- }
- j--;
- }
- i++; j = 15;
- }
-
- /* Fixup result in case the modulus was shifted */
- if (mshift) {
- for (i = mlen - 1; i < 2*mlen - 1; i++)
- a[i] = (a[i] << mshift) | (a[i+1] >> (16-mshift));
- a[2*mlen-1] = a[2*mlen-1] << mshift;
- bigmod(a, m, mlen);
- for (i = 2*mlen - 1; i >= mlen; i--)
- a[i] = (a[i] >> mshift) | (a[i-1] << (16-mshift));
- }
-
- /* Copy result to buffer */
- for (i = 0; i < mlen; i++)
- result[result[0] - i] = a[i+mlen];
-
- /* Free temporary arrays */
- for (i = 0; i < 2*mlen; i++) a[i] = 0; free(a);
- for (i = 0; i < 2*mlen; i++) b[i] = 0; free(b);
- for (i = 0; i < mlen; i++) m[i] = 0; free(m);
- for (i = 0; i < mlen; i++) n[i] = 0; free(n);
-}