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
>= (unsigned long)m0
&&
130 t
> ((unsigned long) r
<< 16) + a
[i
+1])
134 /* Substract q * m from a[i...] */
136 for (k
= len
- 1; k
>= 0; k
--) {
137 t
= (long) q
* (long) m
[k
];
140 if ((unsigned short) t
> a
[i
+k
]) c
++;
141 a
[i
+k
] -= (unsigned short) t
;
144 /* Add back m in case of borrow */
147 for (k
= len
- 1; k
>= 0; k
--) {
150 a
[i
+k
] = (unsigned short)t
;
158 * Compute (base ^ exp) % mod.
159 * The base MUST be smaller than the modulus.
160 * The most significant word of mod MUST be non-zero.
161 * We assume that the result array is the same size as the mod array.
163 static void modpow(Bignum base
, Bignum exp
, Bignum mod
, Bignum result
)
165 unsigned short *a
, *b
, *n
, *m
;
169 /* Allocate m of size mlen, copy mod to m */
170 /* We use big endian internally */
172 m
= malloc(mlen
* sizeof(unsigned short));
173 for (j
= 0; j
< mlen
; j
++) m
[j
] = mod
[mod
[0] - j
];
175 /* Shift m left to make msb bit set */
176 for (mshift
= 0; mshift
< 15; mshift
++)
177 if ((m
[0] << mshift
) & 0x8000) break;
179 for (i
= 0; i
< mlen
- 1; i
++)
180 m
[i
] = (m
[i
] << mshift
) | (m
[i
+1] >> (16-mshift
));
181 m
[mlen
-1] = m
[mlen
-1] << mshift
;
184 /* Allocate n of size mlen, copy base to n */
185 n
= malloc(mlen
* sizeof(unsigned short));
187 for (j
= 0; j
< i
; j
++) n
[j
] = 0;
188 for (j
= 0; j
< base
[0]; j
++) n
[i
+j
] = base
[base
[0] - j
];
190 /* Allocate a and b of size 2*mlen. Set a = 1 */
191 a
= malloc(2 * mlen
* sizeof(unsigned short));
192 b
= malloc(2 * mlen
* sizeof(unsigned short));
193 for (i
= 0; i
< 2*mlen
; i
++) a
[i
] = 0;
196 /* Skip leading zero bits of exp. */
198 while (i
< exp
[0] && (exp
[exp
[0] - i
] & (1 << j
)) == 0) {
200 if (j
< 0) { i
++; j
= 15; }
203 /* Main computation */
206 bigmul(a
+ mlen
, a
+ mlen
, b
, mlen
);
208 if ((exp
[exp
[0] - i
] & (1 << j
)) != 0) {
209 bigmul(b
+ mlen
, n
, a
, mlen
);
220 /* Fixup result in case the modulus was shifted */
222 for (i
= mlen
- 1; i
< 2*mlen
- 1; i
++)
223 a
[i
] = (a
[i
] << mshift
) | (a
[i
+1] >> (16-mshift
));
224 a
[2*mlen
-1] = a
[2*mlen
-1] << mshift
;
226 for (i
= 2*mlen
- 1; i
>= mlen
; i
--)
227 a
[i
] = (a
[i
] >> mshift
) | (a
[i
-1] << (16-mshift
));
230 /* Copy result to buffer */
231 for (i
= 0; i
< mlen
; i
++)
232 result
[result
[0] - i
] = a
[i
+mlen
];
234 /* Free temporary arrays */
235 for (i
= 0; i
< 2*mlen
; i
++) a
[i
] = 0; free(a
);
236 for (i
= 0; i
< 2*mlen
; i
++) b
[i
] = 0; free(b
);
237 for (i
= 0; i
< mlen
; i
++) m
[i
] = 0; free(m
);
238 for (i
= 0; i
< mlen
; i
++) n
[i
] = 0; free(n
);
241 int makekey(unsigned char *data
, struct RSAKey
*result
,
242 unsigned char **keystr
) {
243 unsigned char *p
= data
;
250 result
->bits
= (result
->bits
<< 8) + *p
++;
252 for (j
=0; j
<2; j
++) {
258 result
->bytes
= b
= (w
+7)/8; /* bits -> bytes */
259 w
= (w
+15)/16; /* bits -> words */
263 if (keystr
) *keystr
= p
; /* point at key string, second time */
268 unsigned char byte
= *p
++;
270 bn
[j
][1+i
/2] |= byte
<<8;
272 bn
[j
][1+i
/2] |= byte
;
279 result
->exponent
= bn
[0];
280 result
->modulus
= bn
[1];
285 void rsaencrypt(unsigned char *data
, int length
, struct RSAKey
*key
) {
290 debug(key
->exponent
);
292 memmove(data
+key
->bytes
-length
, data
, length
);
296 for (i
= 2; i
< key
->bytes
-length
-1; i
++) {
298 data
[i
] = random_byte();
299 } while (data
[i
] == 0);
301 data
[key
->bytes
-length
-1] = 0;
303 w
= (key
->bytes
+1)/2;
311 for (i
=key
->bytes
; i
-- ;) {
312 unsigned char byte
= *p
++;
314 b1
[1+i
/2] |= byte
<<8;
321 modpow(b1
, key
->exponent
, key
->modulus
, b2
);
326 for (i
=key
->bytes
; i
-- ;) {
331 b
= b2
[1+i
/2] & 0xFF;
339 int rsastr_len(struct RSAKey
*key
) {
344 return 4 * (ex
[0]+md
[0]) + 10;
347 void rsastr_fmt(char *str
, struct RSAKey
*key
) {
354 for (i
=1; i
<=ex
[0]; i
++) {
355 sprintf(str
+len
, "%04x", ex
[i
]);
356 len
+= strlen(str
+len
);
359 for (i
=1; i
<=md
[0]; i
++) {
360 sprintf(str
+len
, "%04x", md
[i
]);
361 len
+= strlen(str
+len
);
378 unsigned short P1
[2] = { 1, p1
};
379 unsigned short P2
[2] = { 1, p2
};
380 unsigned short P3
[2] = { 1, p3
};
381 unsigned short bigmod
[5] = { 4, 0, 0, 0, 32768U };
382 unsigned short mod
[5] = { 4, 0, 0, 0, 0 };
383 unsigned short a
[5] = { 4, 0, 0, 0, 0 };
384 unsigned short b
[5] = { 4, 0, 0, 0, 0 };
385 unsigned short c
[5] = { 4, 0, 0, 0, 0 };
386 unsigned short One
[2] = { 1, 1 };
387 unsigned short Two
[2] = { 1, 2 };
390 modmult(P1
, P2
, bigmod
, a
); debug(a
);
391 modmult(a
, P3
, bigmod
, mod
); debug(mod
);
393 sub(P1
, One
, a
); debug(a
);
394 sub(P2
, One
, b
); debug(b
);
395 modmult(a
, b
, bigmod
, c
); debug(c
);
396 sub(P3
, One
, a
); debug(a
);
397 modmult(a
, c
, bigmod
, b
); debug(b
);
399 modpow(Two
, b
, mod
, a
); debug(a
);