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1
19
20 package com.maverick.crypto.publickey;
21
22 import com.maverick.crypto.digests.SHA1Digest;
23 import java.math.BigInteger  ;
24 import com.maverick.crypto.security.SecureRandom;
25
26 public final class Dsa {
27
28 public static byte[] sign(BigInteger x,
29 BigInteger p, BigInteger q, BigInteger g,
30 byte[] data) {
31
32 BigInteger hM = new BigInteger (1, data);
33
34 hM = hM.mod(q);
35
36 BigInteger r = g.modPow(x, p).mod(q);
37 BigInteger s = x.modInverse(q).multiply(hM.add(x.multiply(r))).mod(q);
38
39 int dataSz = data.length;
40 byte[] signature = new byte[dataSz * 2];
41 byte[] tmp;
42
43 tmp = unsignedBigIntToBytes(r, dataSz);
44 System.arraycopy(tmp, 0, signature, 0, dataSz);
45
46 tmp = unsignedBigIntToBytes(s, dataSz);
47 System.arraycopy(tmp, 0, signature, dataSz, dataSz);
48
49 return signature;
50 }
51
52 public static boolean verify(BigInteger y,
53 BigInteger p, BigInteger q, BigInteger g,
54 byte[] signature, byte[] data) {
55 int dataSz = signature.length / 2;
56 byte[] ra = new byte[dataSz];
57 byte[] sa = new byte[dataSz];
58
59 System.arraycopy(signature, 0, ra, 0, dataSz);
60 System.arraycopy(signature, dataSz, sa, 0, dataSz);
61
62 BigInteger hM = new BigInteger (1, data);
63 BigInteger r = new BigInteger (1, ra);
64 BigInteger s = new BigInteger (1, sa);
65
66 hM = hM.mod(q);
67
68 BigInteger w = s.modInverse(q);
69 BigInteger u1 = hM.multiply(w).mod(q);
70 BigInteger u2 = r.multiply(w).mod(q);
71 BigInteger v = g.modPow(u1, p).multiply(y.modPow(u2, p)).mod(p).mod(q);
72
73 return (v.compareTo(r) == 0);
74 }
75
76 private static byte[] unsignedBigIntToBytes(BigInteger bi, int size) {
77 byte[] tmp = bi.toByteArray();
78 byte[] tmp2 = null;
79 if (tmp.length > size) {
80 tmp2 = new byte[size];
81 System.arraycopy(tmp, tmp.length - size, tmp2, 0, size);
82 }
83 else if (tmp.length < size) {
84 tmp2 = new byte[size];
85 System.arraycopy(tmp, 0, tmp2, size - tmp.length, tmp.length);
86 }
87 else {
88 tmp2 = tmp;
89 }
90 return tmp2;
91 }
92
93 public static BigInteger generatePublicKey(BigInteger g, BigInteger p,
94 BigInteger x) {
95 return g.modPow(x, p);
96 }
97
98 public static DsaPrivateKey generateKey(int bits, SecureRandom rnd) {
99
100 BigInteger p, q, g, x, y;
101 BigInteger ZERO = BigInteger.valueOf(0);
102 DSAParametersGenerator dsaParams = new DSAParametersGenerator();
103 dsaParams.init(bits, 80, rnd);
104
105 DSAParameters dsa = dsaParams.generateParameters();
106
107 q = dsa.getQ();
108 p = dsa.getP();
109 g = dsa.getG();
110
111 do {
112 x = new BigInteger (160, rnd);
113 }
114 while (x.equals(ZERO) || x.compareTo(q) >= 0);
115
116 y = g.modPow(x, p);
120
121 return new DsaPrivateKey(p, q, g, x);
122 }
123
124 }
125
126
129 class DSAParametersGenerator {
130 private int size;
131 private int certainty;
132 private SecureRandom random;
133
134 private static BigInteger ONE = BigInteger.valueOf(1);
135 private static BigInteger TWO = BigInteger.valueOf(2);
136
137
144 public void init(
145 int size,
146 int certainty,
147 SecureRandom random) {
148 this.size = size;
149 this.certainty = certainty;
150 this.random = random;
151 }
152
153
158 private void add(
159 byte[] a,
160 byte[] b,
161 int value) {
162 int x = (b[b.length - 1] & 0xff) + value;
163
164 a[b.length - 1] = (byte) x;
165 x >>>= 8;
166
167 for (int i = b.length - 2; i >= 0; i--) {
168 x += (b[i] & 0xff);
169 a[i] = (byte) x;
170 x >>>= 8;
171 }
172 }
173
174
180 public DSAParameters generateParameters() {
181 byte[] seed = new byte[20];
182 byte[] part1 = new byte[20];
183 byte[] part2 = new byte[20];
184 byte[] u = new byte[20];
185 SHA1Digest sha1 = new SHA1Digest();
186 int n = (size - 1) / 160;
187 byte[] w = new byte[size / 8];
188
189 BigInteger q = null, p = null, g = null;
190 int counter = 0;
191 boolean primesFound = false;
192
193 while (!primesFound) {
194 do {
195 random.nextBytes(seed);
196
197 sha1.update(seed, 0, seed.length);
198
199 sha1.doFinal(part1, 0);
200
201 System.arraycopy(seed, 0, part2, 0, seed.length);
202
203 add(part2, seed, 1);
204
205 sha1.update(part2, 0, part2.length);
206
207 sha1.doFinal(part2, 0);
208
209 for (int i = 0; i != u.length; i++) {
210 u[i] = (byte) (part1[i] ^ part2[i]);
211 }
212
213 u[0] |= (byte) 0x80;
214 u[19] |= (byte) 0x01;
215
216 q = new BigInteger (1, u);
217 }
218 while (!q.isProbablePrime(certainty));
219
220 counter = 0;
221
222 int offset = 2;
223
224 while (counter < 4096) {
225 for (int k = 0; k < n; k++) {
226 add(part1, seed, offset + k);
227 sha1.update(part1, 0, part1.length);
228 sha1.doFinal(part1, 0);
229 System.arraycopy(part1, 0, w, w.length - (k + 1) * part1.length,
230 part1.length);
231 }
232
233 add(part1, seed, offset + n);
234 sha1.update(part1, 0, part1.length);
235 sha1.doFinal(part1, 0);
236 System.arraycopy(part1, part1.length - ( (w.length - (n) * part1.length)),
237 w, 0, w.length - n * part1.length);
238
239 w[0] |= (byte) 0x80;
240
241 BigInteger x = new BigInteger (1, w);
242
243 BigInteger c = x.mod(q.multiply(TWO));
244
245 p = x.subtract(c.subtract(ONE));
246
247 if (p.testBit(size - 1)) {
248 if (p.isProbablePrime(certainty)) {
249 primesFound = true;
250 break;
251 }
252 }
253
254 counter += 1;
255 offset += n + 1;
256 }
257 }
258
259 BigInteger pMinusOneOverQ = p.subtract(ONE).divide(q);
263
264 for (; ; ) {
265 BigInteger h = new BigInteger (size, random);
266 if (h.compareTo(ONE) <= 0 || h.compareTo(p.subtract(ONE)) >= 0) {
267 continue;
268 }
269
270 g = h.modPow(pMinusOneOverQ, p);
271 if (g.compareTo(ONE) <= 0) {
272 continue;
273 }
274
275 break;
276 }
277
278 return new DSAParameters(p, q, g, new DSAValidationParameters(seed, counter));
279 }
280 }
281
282 class DSAParameters
283
284 {
285 private BigInteger g;
286 private BigInteger q;
287 private BigInteger p;
288 private DSAValidationParameters validation;
289
290 public DSAParameters(
291 BigInteger p,
292 BigInteger q,
293 BigInteger g) {
294 this.g = g;
295 this.p = p;
296 this.q = q;
297 }
298
299 public DSAParameters(
300 BigInteger p,
301 BigInteger q,
302 BigInteger g,
303 DSAValidationParameters params) {
304 this.g = g;
305 this.p = p;
306 this.q = q;
307 this.validation = params;
308 }
309
310 public BigInteger getP() {
311 return p;
312 }
313
314 public BigInteger getQ() {
315 return q;
316 }
317
318 public BigInteger getG() {
319 return g;
320 }
321
322 public DSAValidationParameters getValidationParameters() {
323 return validation;
324 }
325
326 public boolean equals(
327 Object obj) {
328 if (! (obj instanceof DSAParameters)) {
329 return false;
330 }
331
332 DSAParameters pm = (DSAParameters) obj;
333
334 return (pm.getP().equals(p) && pm.getQ().equals(q) && pm.getG().equals(g));
335 }
336 }
337
338 class DSAValidationParameters {
339 private byte[] seed;
340 private int counter;
341
342 public DSAValidationParameters(
343 byte[] seed,
344 int counter) {
345 this.seed = seed;
346 this.counter = counter;
347 }
348
349 public int getCounter() {
350 return counter;
351 }
352
353 public byte[] getSeed() {
354 return seed;
355 }
356
357 public boolean equals(
358 Object o) {
359 if (o == null || ! (o instanceof DSAValidationParameters)) {
360 return false;
361 }
362
363 DSAValidationParameters other = (DSAValidationParameters) o;
364
365 if (other.counter != this.counter) {
366 return false;
367 }
368
369 if (other.seed.length != this.seed.length) {
370 return false;
371 }
372
373 for (int i = 0; i != other.seed.length; i++) {
374 if (other.seed[i] != this.seed[i]) {
375 return false;
376 }
377 }
378
379 return true;
380 }
381 }
382 |
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