2 * RSA implementation just sufficient for ssh client-side
5 * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
14 typedef unsigned short *Bignum;
16 static unsigned short Zero[1] = { 0 };
18 #if defined TESTMODE || defined RSADEBUG
22 #define debug(x) bndebug(#x,x)
24 static void bndebug(char *name, Bignum b) {
26 int w = 50-level-strlen(name)-5*b[0];
30 dprintf("%*s%s%*s", level, "", name, w, "");
31 for (i=b[0]; i>0; i--)
32 dprintf(" %04x", b[i]);
35 #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0)
36 #define enter(x) do { dmsg(x); level += 4; } while(0)
37 #define leave(x) do { level -= 4; dmsg(x); } while(0)
45 static Bignum newbn(int length) {
46 Bignum b = malloc((length+1)*sizeof(unsigned short));
53 static void freebn(Bignum b) {
59 * Input is in the first len words of a and b.
60 * Result is returned in the first 2*len words of c.
62 static void bigmul(unsigned short *a, unsigned short *b, unsigned short *c,
68 for (j = len - 1; j >= 0; j--)
71 for (i = len - 1; i >= 0; i--) {
74 for (j = len - 1; j >= 0; j--) {
75 t += ai * (unsigned long) b[j];
76 t += (unsigned long) c[i+j+1];
77 c[i+j+1] = (unsigned short)t;
80 c[i] = (unsigned short)t;
86 * Input in first 2*len words of a and first len words of m.
87 * Output in first 2*len words of a (of which first len words will be zero).
88 * The MSW of m MUST have its high bit set.
90 static void bigmod(unsigned short *a, unsigned short *m, int len)
92 unsigned short m0, m1;
96 /* Special case for len == 1 */
98 a[1] = (((long) a[0] << 16) + a[1]) % m[0];
106 for (i = 0; i <= len; i++) {
108 unsigned int q, r, c;
117 /* Find q = h:a[i] / m0 */
118 t = ((unsigned long) h << 16) + a[i];
122 /* Refine our estimate of q by looking at
123 h:a[i]:a[i+1] / m0:m1 */
124 t = (long) m1 * (long) q;
125 if (t > ((unsigned long) r << 16) + a[i+1]) {
128 r = (r + m0) & 0xffff; /* overflow? */
129 if (r >= m0 && t > ((unsigned long) r << 16) + a[i+1])
133 /* Substract q * m from a[i...] */
135 for (k = len - 1; k >= 0; k--) {
136 t = (long) q * (long) m[k];
139 if ((unsigned short) t > a[i+k]) c++;
140 a[i+k] -= (unsigned short) t;
143 /* Add back m in case of borrow */
146 for (k = len - 1; k >= 0; k--) {
149 a[i+k] = (unsigned short)t;
157 * Compute (base ^ exp) % mod.
158 * The base MUST be smaller than the modulus.
159 * The most significant word of mod MUST be non-zero.
160 * We assume that the result array is the same size as the mod array.
162 static void modpow(Bignum base, Bignum exp, Bignum mod, Bignum result)
164 unsigned short *a, *b, *n, *m;
168 /* Allocate m of size mlen, copy mod to m */
169 /* We use big endian internally */
171 m = malloc(mlen * sizeof(unsigned short));
172 for (j = 0; j < mlen; j++) m[j] = mod[mod[0] - j];
174 /* Shift m left to make msb bit set */
175 for (mshift = 0; mshift < 15; mshift++)
176 if ((m[0] << mshift) & 0x8000) break;
178 for (i = 0; i < mlen - 1; i++)
179 m[i] = (m[i] << mshift) | (m[i+1] >> (16-mshift));
180 m[mlen-1] = m[mlen-1] << mshift;
183 /* Allocate n of size mlen, copy base to n */
184 n = malloc(mlen * sizeof(unsigned short));
186 for (j = 0; j < i; j++) n[j] = 0;
187 for (j = 0; j < base[0]; j++) n[i+j] = base[base[0] - j];
189 /* Allocate a and b of size 2*mlen. Set a = 1 */
190 a = malloc(2 * mlen * sizeof(unsigned short));
191 b = malloc(2 * mlen * sizeof(unsigned short));
192 for (i = 0; i < 2*mlen; i++) a[i] = 0;
195 /* Skip leading zero bits of exp. */
197 while (i < exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) {
199 if (j < 0) { i++; j = 15; }
202 /* Main computation */
205 bigmul(a + mlen, a + mlen, b, mlen);
207 if ((exp[exp[0] - i] & (1 << j)) != 0) {
208 bigmul(b + mlen, n, a, mlen);
219 /* Fixup result in case the modulus was shifted */
221 for (i = mlen - 1; i < 2*mlen - 1; i++)
222 a[i] = (a[i] << mshift) | (a[i+1] >> (16-mshift));
223 a[2*mlen-1] = a[2*mlen-1] << mshift;
225 for (i = 2*mlen - 1; i >= mlen; i--)
226 a[i] = (a[i] >> mshift) | (a[i-1] << (16-mshift));
229 /* Copy result to buffer */
230 for (i = 0; i < mlen; i++)
231 result[result[0] - i] = a[i+mlen];
233 /* Free temporary arrays */
234 for (i = 0; i < 2*mlen; i++) a[i] = 0; free(a);
235 for (i = 0; i < 2*mlen; i++) b[i] = 0; free(b);
236 for (i = 0; i < mlen; i++) m[i] = 0; free(m);
237 for (i = 0; i < mlen; i++) n[i] = 0; free(n);
240 int makekey(unsigned char *data, struct RSAKey *result,
241 unsigned char **keystr) {
242 unsigned char *p = data;
249 result->bits = (result->bits << 8) + *p++;
251 for (j=0; j<2; j++) {
257 result->bytes = b = (w+7)/8; /* bits -> bytes */
258 w = (w+15)/16; /* bits -> words */
262 if (keystr) *keystr = p; /* point at key string, second time */
266 for (i=0; i<b; i++) {
267 unsigned char byte = *p++;
269 bn[j][w-i/2] |= byte;
271 bn[j][w-i/2] |= byte<<8;
278 result->exponent = bn[0];
279 result->modulus = bn[1];
284 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
289 debug(key->exponent);
291 memmove(data+key->bytes-length, data, length);
295 for (i = 2; i < key->bytes-length-1; i++) {
297 data[i] = random_byte();
298 } while (data[i] == 0);
300 data[key->bytes-length-1] = 0;
302 w = (key->bytes+1)/2;
310 for (i=0; i<key->bytes; i++) {
311 unsigned char byte = *p++;
312 if ((key->bytes-i) & 1)
315 b1[w-i/2] |= byte<<8;
320 modpow(b1, key->exponent, key->modulus, b2);
325 for (i=0; i<key->bytes; i++) {
328 b = b2[w-i/2] & 0xFF;
338 int rsastr_len(struct RSAKey *key) {
343 return 4 * (ex[0]+md[0]) + 10;
346 void rsastr_fmt(char *str, struct RSAKey *key) {
353 for (i=1; i<=ex[0]; i++) {
354 sprintf(str+len, "%04x", ex[i]);
355 len += strlen(str+len);
358 for (i=1; i<=md[0]; i++) {
359 sprintf(str+len, "%04x", md[i]);
360 len += strlen(str+len);
377 unsigned short P1[2] = { 1, p1 };
378 unsigned short P2[2] = { 1, p2 };
379 unsigned short P3[2] = { 1, p3 };
380 unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U };
381 unsigned short mod[5] = { 4, 0, 0, 0, 0 };
382 unsigned short a[5] = { 4, 0, 0, 0, 0 };
383 unsigned short b[5] = { 4, 0, 0, 0, 0 };
384 unsigned short c[5] = { 4, 0, 0, 0, 0 };
385 unsigned short One[2] = { 1, 1 };
386 unsigned short Two[2] = { 1, 2 };
389 modmult(P1, P2, bigmod, a); debug(a);
390 modmult(a, P3, bigmod, mod); debug(mod);
392 sub(P1, One, a); debug(a);
393 sub(P2, One, b); debug(b);
394 modmult(a, b, bigmod, c); debug(c);
395 sub(P3, One, a); debug(a);
396 modmult(a, c, bigmod, b); debug(b);
398 modpow(Two, b, mod, a); debug(a);