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1.1 root 1: # include <stdio.h>
2: /* file nbs.c
3: This file has the necessary procedures to use the NBS algorithm
4: to encrypt and decrypt strings of arbitrary length.
5:
6: Basically
7:
8: ciphertext = nbsencrypt(cleartext,secretkey,ciphertext);
9:
10: yields a string ciphertext from string cleartext using
11: the secret string secretkey.
12: Then
13:
14: cleartext = nbsdecrypt(ciphertext,secretkey,cleartext);
15:
16: yields the original string cleartext IF the string secretkey
17: is the same for both calls.
18: The third parameter is filled with the result of the call-
19: it must be (11/8)*size(firstarg).
20: The first and third areguments must be different.
21: The cleartext must be ASCII - the top eighth bit is ignored,
22: so binary data won't work.
23: The plaintext is broken into 8 character sections,
24: encrypted, and concatenated separated by $'s to make the ciphertext.
25: The first 8 letter section uses the secretkey, subsequent
26: sections use the cleartext of the previous section as
27: the key.
28: Thus the ciphertext depends on itself, except for
29: the first section, which depends on the key.
30: This means that sections of the ciphertext, except the first,
31: may not stand alone.
32: Only the first 8 characters of the key matter.
33: */
34: char *deblknot(), *deblkclr();
35: char *nbs8decrypt(), *nbs8encrypt();
36: static char E[48];
37: char e[];
38: char *nbsencrypt(str,key,result)
39: char *result;
40: register char *str, *key; {
41: static char buf[20],oldbuf[20];
42: register int j;
43: result[0] = 0;
44: strcpy(oldbuf,key);
45: while(*str){
46: for(j=0;j<10;j++)buf[j] = 0;
47: for(j=0;j<8 && *str;j++)buf[j] = *str++;
48: strcat(result,nbs8encrypt(buf,oldbuf));
49: strcat(result,"$");
50: strcpy(oldbuf,buf);
51: }
52: return(result);
53: }
54: char *nbsdecrypt(cpt,key,result)
55: char *result;
56: register char *cpt,*key; {
57: register char *s;
58: char c,oldbuf[20];
59: result[0] = 0;
60: strcpy(oldbuf,key);
61: while(*cpt){
62: for(s = cpt;*s && *s != '$';s++);
63: c = *s;
64: *s = 0;
65: strcpy(oldbuf,nbs8decrypt(cpt,oldbuf));
66: strcat(result,oldbuf);
67: if(c == 0)break;
68: cpt = s + 1;
69: }
70: return(result);
71: }
72: /* make key to be sent across the network */
73: makeuukey(skey,sn,mch)
74: char *skey, *sn, mch;
75: {
76: skey[0] = mch;
77: skey[1] = 0;
78: strcat(skey,sn);
79: }
80:
81: /* all other calls are private */
82: /*
83: char _sobuf[BUFSIZ];
84: testing(){
85: static char res[BUFSIZ];
86: register char *s;
87: char str[BUFSIZ];
88: setbuf(stdout,_sobuf);
89: while(!feof(stdin)){
90: fprintf(stderr,"String:\n");
91: fgets(str,BUFSIZ,stdin);
92: if(feof(stdin))break;
93: strcat(str,"\n");
94: s = nbsencrypt(str,"hellothere",res);
95: fprintf(stderr,"encrypted:\n%s\n",s);
96: fprintf(stderr,"decrypted:\n");
97: printf("%s",nbsdecrypt(s,"hellothere",str));
98: fprintf(stderr,"\n");
99: }
100: }
101: */
102: /*
103: To encrypt:
104: The first level of call splits the input strings into strings
105: no longer than 8 characters, for encryption.
106: Then the encryption of 8 characters breaks all but the top bit
107: of each character into a 64-character block, each character
108: with 1 or 0 corresponding to binary.
109: The key is set likewise.
110: The encrypted form is then converted, 6 bits at a time,
111: into an ASCII string.
112:
113: To decrypt:
114: We take the result of the encryption, 6 significant bits
115: per character, and convert it to the block(64-char) fmt.
116: This is decrypted by running the nbs algorithm in reverse,
117: and transformed back into 7bit ASCII.
118:
119: The subroutines to do ASCII blocking and deblocking
120: are .....clr and the funny 6-bit code are .....not.
121:
122: */
123:
124: char *nbs8encrypt(str,key)
125: register char *str, *key; {
126: static char keyblk[100], blk[100];
127: register int i;
128:
129: enblkclr(keyblk,key);
130: nbssetkey(keyblk);
131:
132: for(i=0;i<48;i++) E[i] = e[i];
133: enblkclr(blk,str);
134: blkencrypt(blk,0); /* forward dir */
135:
136: return(deblknot(blk));
137: }
138: char *nbs8decrypt(crp,key)
139: register char *crp, *key; {
140: static char keyblk[100], blk[100];
141: register int i;
142:
143: enblkclr(keyblk,key);
144: nbssetkey(keyblk);
145:
146: for(i=0;i<48;i++) E[i] = e[i];
147: enblknot(blk,crp);
148: blkencrypt(blk,1); /* backward dir */
149:
150: return(deblkclr(blk));
151: }
152: enblkclr(blk,str) /* ignores top bit of chars in string str */
153: char *blk,*str; {
154: register int i,j;
155: register char c;
156: for(i=0;i<70;i++)blk[i] = 0;
157: for(i=0; (c= *str) && i<64; str++){
158: for(j=0; j<7; j++, i++)
159: blk[i] = (c>>(6-j)) & 01;
160: i++;
161: }
162: }
163: char *deblkclr(blk)
164: char *blk; {
165: register int i,j;
166: register char c;
167: static char iobuf[30];
168: for(i=0; i<10; i++){
169: c = 0;
170: for(j=0; j<7; j++){
171: c <<= 1;
172: c |= blk[8*i+j];
173: }
174: iobuf[i] = c;
175: }
176: iobuf[i] = 0;
177: return(iobuf);
178: }
179: enblknot(blk,crp)
180: char *blk;
181: char *crp; {
182: register int i,j;
183: register char c;
184: for(i=0;i<70;i++)blk[i] = 0;
185: for(i=0; (c= *crp) && i<64; crp++){
186: if(c>'Z') c -= 6;
187: if(c>'9') c -= 7;
188: c -= '.';
189: for(j=0; j<6; j++, i++)
190: blk[i] = (c>>(5-j)) & 01;
191: }
192: }
193: char *deblknot(blk)
194: char *blk; {
195: register int i,j;
196: register char c;
197: static char iobuf[30];
198: for(i=0; i<11; i++){
199: c = 0;
200: for(j=0; j<6; j++){
201: c <<= 1;
202: c |= blk[6*i+j];
203: }
204: c += '.';
205: if(c > '9')c += 7;
206: if(c > 'Z')c += 6;
207: iobuf[i] = c;
208: }
209: iobuf[i] = 0;
210: return(iobuf);
211: }
212: /*
213: * This program implements the
214: * Proposed Federal Information Processing
215: * Data Encryption Standard.
216: * See Federal Register, March 17, 1975 (40FR12134)
217: */
218:
219: /*
220: * Initial permutation,
221: */
222: static char IP[] = {
223: 58,50,42,34,26,18,10, 2,
224: 60,52,44,36,28,20,12, 4,
225: 62,54,46,38,30,22,14, 6,
226: 64,56,48,40,32,24,16, 8,
227: 57,49,41,33,25,17, 9, 1,
228: 59,51,43,35,27,19,11, 3,
229: 61,53,45,37,29,21,13, 5,
230: 63,55,47,39,31,23,15, 7,
231: };
232:
233: /*
234: * Final permutation, FP = IP^(-1)
235: */
236: static char FP[] = {
237: 40, 8,48,16,56,24,64,32,
238: 39, 7,47,15,55,23,63,31,
239: 38, 6,46,14,54,22,62,30,
240: 37, 5,45,13,53,21,61,29,
241: 36, 4,44,12,52,20,60,28,
242: 35, 3,43,11,51,19,59,27,
243: 34, 2,42,10,50,18,58,26,
244: 33, 1,41, 9,49,17,57,25,
245: };
246:
247: /*
248: * Permuted-choice 1 from the key bits
249: * to yield C and D.
250: * Note that bits 8,16... are left out:
251: * They are intended for a parity check.
252: */
253: static char PC1_C[] = {
254: 57,49,41,33,25,17, 9,
255: 1,58,50,42,34,26,18,
256: 10, 2,59,51,43,35,27,
257: 19,11, 3,60,52,44,36,
258: };
259:
260: static char PC1_D[] = {
261: 63,55,47,39,31,23,15,
262: 7,62,54,46,38,30,22,
263: 14, 6,61,53,45,37,29,
264: 21,13, 5,28,20,12, 4,
265: };
266:
267: /*
268: * Sequence of shifts used for the key schedule.
269: */
270: static char shifts[] = {
271: 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1,
272: };
273:
274: /*
275: * Permuted-choice 2, to pick out the bits from
276: * the CD array that generate the key schedule.
277: */
278: static char PC2_C[] = {
279: 14,17,11,24, 1, 5,
280: 3,28,15, 6,21,10,
281: 23,19,12, 4,26, 8,
282: 16, 7,27,20,13, 2,
283: };
284:
285: static char PC2_D[] = {
286: 41,52,31,37,47,55,
287: 30,40,51,45,33,48,
288: 44,49,39,56,34,53,
289: 46,42,50,36,29,32,
290: };
291:
292: /*
293: * The C and D arrays used to calculate the key schedule.
294: */
295:
296: static char C[28];
297: static char D[28];
298: /*
299: * The key schedule.
300: * Generated from the key.
301: */
302: static char KS[16][48];
303:
304: /*
305: * Set up the key schedule from the key.
306: */
307:
308: nbssetkey(key)
309: char *key;
310: {
311: register i, j, k;
312: int t;
313:
314: /*
315: * First, generate C and D by permuting
316: * the key. The low order bit of each
317: * 8-bit char is not used, so C and D are only 28
318: * bits apiece.
319: */
320: for (i=0; i<28; i++) {
321: C[i] = key[PC1_C[i]-1];
322: D[i] = key[PC1_D[i]-1];
323: }
324: /*
325: * To generate Ki, rotate C and D according
326: * to schedule and pick up a permutation
327: * using PC2.
328: */
329: for (i=0; i<16; i++) {
330: /*
331: * rotate.
332: */
333: for (k=0; k<shifts[i]; k++) {
334: t = C[0];
335: for (j=0; j<28-1; j++)
336: C[j] = C[j+1];
337: C[27] = t;
338: t = D[0];
339: for (j=0; j<28-1; j++)
340: D[j] = D[j+1];
341: D[27] = t;
342: }
343: /*
344: * get Ki. Note C and D are concatenated.
345: */
346: for (j=0; j<24; j++) {
347: KS[i][j] = C[PC2_C[j]-1];
348: KS[i][j+24] = D[PC2_D[j]-28-1];
349: }
350: }
351: }
352:
353: /*
354: * The E bit-selection table.
355: */
356: static char e[] = {
357: 32, 1, 2, 3, 4, 5,
358: 4, 5, 6, 7, 8, 9,
359: 8, 9,10,11,12,13,
360: 12,13,14,15,16,17,
361: 16,17,18,19,20,21,
362: 20,21,22,23,24,25,
363: 24,25,26,27,28,29,
364: 28,29,30,31,32, 1,
365: };
366:
367: /*
368: * The 8 selection functions.
369: * For some reason, they give a 0-origin
370: * index, unlike everything else.
371: */
372: static char S[8][64] = {
373: 14, 4,13, 1, 2,15,11, 8, 3,10, 6,12, 5, 9, 0, 7,
374: 0,15, 7, 4,14, 2,13, 1,10, 6,12,11, 9, 5, 3, 8,
375: 4, 1,14, 8,13, 6, 2,11,15,12, 9, 7, 3,10, 5, 0,
376: 15,12, 8, 2, 4, 9, 1, 7, 5,11, 3,14,10, 0, 6,13,
377:
378: 15, 1, 8,14, 6,11, 3, 4, 9, 7, 2,13,12, 0, 5,10,
379: 3,13, 4, 7,15, 2, 8,14,12, 0, 1,10, 6, 9,11, 5,
380: 0,14, 7,11,10, 4,13, 1, 5, 8,12, 6, 9, 3, 2,15,
381: 13, 8,10, 1, 3,15, 4, 2,11, 6, 7,12, 0, 5,14, 9,
382:
383: 10, 0, 9,14, 6, 3,15, 5, 1,13,12, 7,11, 4, 2, 8,
384: 13, 7, 0, 9, 3, 4, 6,10, 2, 8, 5,14,12,11,15, 1,
385: 13, 6, 4, 9, 8,15, 3, 0,11, 1, 2,12, 5,10,14, 7,
386: 1,10,13, 0, 6, 9, 8, 7, 4,15,14, 3,11, 5, 2,12,
387:
388: 7,13,14, 3, 0, 6, 9,10, 1, 2, 8, 5,11,12, 4,15,
389: 13, 8,11, 5, 6,15, 0, 3, 4, 7, 2,12, 1,10,14, 9,
390: 10, 6, 9, 0,12,11, 7,13,15, 1, 3,14, 5, 2, 8, 4,
391: 3,15, 0, 6,10, 1,13, 8, 9, 4, 5,11,12, 7, 2,14,
392:
393: 2,12, 4, 1, 7,10,11, 6, 8, 5, 3,15,13, 0,14, 9,
394: 14,11, 2,12, 4, 7,13, 1, 5, 0,15,10, 3, 9, 8, 6,
395: 4, 2, 1,11,10,13, 7, 8,15, 9,12, 5, 6, 3, 0,14,
396: 11, 8,12, 7, 1,14, 2,13, 6,15, 0, 9,10, 4, 5, 3,
397:
398: 12, 1,10,15, 9, 2, 6, 8, 0,13, 3, 4,14, 7, 5,11,
399: 10,15, 4, 2, 7,12, 9, 5, 6, 1,13,14, 0,11, 3, 8,
400: 9,14,15, 5, 2, 8,12, 3, 7, 0, 4,10, 1,13,11, 6,
401: 4, 3, 2,12, 9, 5,15,10,11,14, 1, 7, 6, 0, 8,13,
402:
403: 4,11, 2,14,15, 0, 8,13, 3,12, 9, 7, 5,10, 6, 1,
404: 13, 0,11, 7, 4, 9, 1,10,14, 3, 5,12, 2,15, 8, 6,
405: 1, 4,11,13,12, 3, 7,14,10,15, 6, 8, 0, 5, 9, 2,
406: 6,11,13, 8, 1, 4,10, 7, 9, 5, 0,15,14, 2, 3,12,
407:
408: 13, 2, 8, 4, 6,15,11, 1,10, 9, 3,14, 5, 0,12, 7,
409: 1,15,13, 8,10, 3, 7, 4,12, 5, 6,11, 0,14, 9, 2,
410: 7,11, 4, 1, 9,12,14, 2, 0, 6,10,13,15, 3, 5, 8,
411: 2, 1,14, 7, 4,10, 8,13,15,12, 9, 0, 3, 5, 6,11,
412: };
413:
414: /*
415: * P is a permutation on the selected combination
416: * of the current L and key.
417: */
418: static char P[] = {
419: 16, 7,20,21,
420: 29,12,28,17,
421: 1,15,23,26,
422: 5,18,31,10,
423: 2, 8,24,14,
424: 32,27, 3, 9,
425: 19,13,30, 6,
426: 22,11, 4,25,
427: };
428:
429: /*
430: * The current block, divided into 2 halves.
431: */
432: static char L[32], R[32];
433: static char tempL[32];
434: static char f[32];
435:
436: /*
437: * The combination of the key and the input, before selection.
438: */
439: static char preS[48];
440:
441: /*
442: * The payoff: encrypt a block.
443: */
444:
445: blkencrypt(block, edflag)
446: char *block;
447: {
448: int i, ii;
449: register t, j, k;
450:
451: /*
452: * First, permute the bits in the input
453: */
454: for (j=0; j<64; j++)
455: L[j] = block[IP[j]-1];
456: /*
457: * Perform an encryption operation 16 times.
458: */
459: for (ii=0; ii<16; ii++) {
460: /*
461: * Set direction
462: */
463: if (edflag)
464: i = 15-ii;
465: else
466: i = ii;
467: /*
468: * Save the R array,
469: * which will be the new L.
470: */
471: for (j=0; j<32; j++)
472: tempL[j] = R[j];
473: /*
474: * Expand R to 48 bits using the E selector;
475: * exclusive-or with the current key bits.
476: */
477: for (j=0; j<48; j++)
478: preS[j] = R[E[j]-1] ^ KS[i][j];
479: /*
480: * The pre-select bits are now considered
481: * in 8 groups of 6 bits each.
482: * The 8 selection functions map these
483: * 6-bit quantities into 4-bit quantities
484: * and the results permuted
485: * to make an f(R, K).
486: * The indexing into the selection functions
487: * is peculiar; it could be simplified by
488: * rewriting the tables.
489: */
490: for (j=0; j<8; j++) {
491: t = 6*j;
492: k = S[j][(preS[t+0]<<5)+
493: (preS[t+1]<<3)+
494: (preS[t+2]<<2)+
495: (preS[t+3]<<1)+
496: (preS[t+4]<<0)+
497: (preS[t+5]<<4)];
498: t = 4*j;
499: f[t+0] = (k>>3)&01;
500: f[t+1] = (k>>2)&01;
501: f[t+2] = (k>>1)&01;
502: f[t+3] = (k>>0)&01;
503: }
504: /*
505: * The new R is L ^ f(R, K).
506: * The f here has to be permuted first, though.
507: */
508: for (j=0; j<32; j++)
509: R[j] = L[j] ^ f[P[j]-1];
510: /*
511: * Finally, the new L (the original R)
512: * is copied back.
513: */
514: for (j=0; j<32; j++)
515: L[j] = tempL[j];
516: }
517: /*
518: * The output L and R are reversed.
519: */
520: for (j=0; j<32; j++) {
521: t = L[j];
522: L[j] = R[j];
523: R[j] = t;
524: }
525: /*
526: * The final output
527: * gets the inverse permutation of the very original.
528: */
529: for (j=0; j<64; j++)
530: block[j] = L[FP[j]-1];
531: }
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