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1.1 root 1: static char sccsid[] = "@(#)nbs.c 4.1 (Berkeley) 9/12/82";
2:
3: # include <stdio.h>
4: /* sccs id variable */
5: static char *nbs_sid = "@(#)nbs.c 1.2";
6:
7: /* file nbs.c
8: This file has the necessary procedures to use the NBS algorithm
9: to encrypt and decrypt strings of arbitrary length.
10:
11: Basically
12:
13: ciphertext = nbsencrypt(cleartext,secretkey,ciphertext);
14:
15: yields a string ciphertext from string cleartext using
16: the secret string secretkey.
17: Then
18:
19: cleartext = nbsdecrypt(ciphertext,secretkey,cleartext);
20:
21: yields the original string cleartext IF the string secretkey
22: is the same for both calls.
23: The third parameter is filled with the result of the call-
24: it must be (11/8)*size(firstarg).
25: The first and third areguments must be different.
26: The cleartext must be ASCII - the top eighth bit is ignored,
27: so binary data won't work.
28: The plaintext is broken into 8 character sections,
29: encrypted, and concatenated separated by $'s to make the ciphertext.
30: The first 8 letter section uses the secretkey, subsequent
31: sections use the cleartext of the previous section as
32: the key.
33: Thus the ciphertext depends on itself, except for
34: the first section, which depends on the key.
35: This means that sections of the ciphertext, except the first,
36: may not stand alone.
37: Only the first 8 characters of the key matter.
38: */
39: char *deblknot(), *deblkclr();
40: char *nbs8decrypt(), *nbs8encrypt();
41: static char E[48];
42: char e[];
43: char *nbsencrypt(str,key,result)
44: char *result;
45: char *str, *key; {
46: static char buf[20],oldbuf[20];
47: register int j;
48: result[0] = 0;
49: strcpy(oldbuf,key);
50: while(*str){
51: for(j=0;j<10;j++)buf[j] = 0;
52: for(j=0;j<8 && *str;j++)buf[j] = *str++;
53: strcat(result,nbs8encrypt(buf,oldbuf));
54: strcat(result,"$");
55: strcpy(oldbuf,buf);
56: }
57: return(result);
58: }
59: char *nbsdecrypt(cpt,key,result)
60: char *result;
61: char *cpt,*key; {
62: char *s;
63: char c,oldbuf[20];
64: result[0] = 0;
65: strcpy(oldbuf,key);
66: while(*cpt){
67: for(s = cpt;*s && *s != '$';s++);
68: c = *s;
69: *s = 0;
70: strcpy(oldbuf,nbs8decrypt(cpt,oldbuf));
71: strcat(result,oldbuf);
72: if(c == 0)break;
73: cpt = s + 1;
74: }
75: return(result);
76: }
77: /* make key to be sent across the network */
78: makeuukey(skey,sn,mch)
79: char *skey, *sn, mch;
80: {
81: skey[0] = mch;
82: skey[1] = 0;
83: strcat(skey,sn);
84: }
85:
86: /* all other calls are private */
87: /*
88: char _sobuf[BUFSIZ];
89: testing(){
90: static char res[BUFSIZ];
91: char *s;
92: char str[BUFSIZ];
93: setbuf(stdout,_sobuf);
94: while(!feof(stdin)){
95: fprintf(stderr,"String:\n");
96: fgets(str,BUFSIZ,stdin);
97: if(feof(stdin))break;
98: strcat(str,"\n");
99: s = nbsencrypt(str,"hellothere",res);
100: fprintf(stderr,"encrypted:\n%s\n",s);
101: fprintf(stderr,"decrypted:\n");
102: printf("%s",nbsdecrypt(s,"hellothere",str));
103: fprintf(stderr,"\n");
104: }
105: }
106: */
107: /*
108: To encrypt:
109: The first level of call splits the input strings into strings
110: no longer than 8 characters, for encryption.
111: Then the encryption of 8 characters breaks all but the top bit
112: of each character into a 64-character block, each character
113: with 1 or 0 corresponding to binary.
114: The key is set likewise.
115: The encrypted form is then converted, 6 bits at a time,
116: into an ASCII string.
117:
118: To decrypt:
119: We take the result of the encryption, 6 significant bits
120: per character, and convert it to the block(64-char) fmt.
121: This is decrypted by running the nbs algorithm in reverse,
122: and transformed back into 7bit ASCII.
123:
124: The subroutines to do ASCII blocking and deblocking
125: are .....clr and the funny 6-bit code are .....not.
126:
127: */
128:
129: char *nbs8encrypt(str,key)
130: char *str, *key; {
131: static char keyblk[100], blk[100];
132: register int i;
133:
134: enblkclr(keyblk,key);
135: nbssetkey(keyblk);
136:
137: for(i=0;i<48;i++) E[i] = e[i];
138: enblkclr(blk,str);
139: blkencrypt(blk,0); /* forward dir */
140:
141: return(deblknot(blk));
142: }
143: char *nbs8decrypt(crp,key)
144: char *crp, *key; {
145: static char keyblk[100], blk[100];
146: register int i;
147:
148: enblkclr(keyblk,key);
149: nbssetkey(keyblk);
150:
151: for(i=0;i<48;i++) E[i] = e[i];
152: enblknot(blk,crp);
153: blkencrypt(blk,1); /* backward dir */
154:
155: return(deblkclr(blk));
156: }
157: enblkclr(blk,str) /* ignores top bit of chars in string str */
158: char *blk,*str; {
159: register int i,j;
160: char c;
161: for(i=0;i<70;i++)blk[i] = 0;
162: for(i=0; (c= *str) && i<64; str++){
163: for(j=0; j<7; j++, i++)
164: blk[i] = (c>>(6-j)) & 01;
165: i++;
166: }
167: }
168: char *deblkclr(blk)
169: char *blk; {
170: register int i,j;
171: char c;
172: static char iobuf[30];
173: for(i=0; i<10; i++){
174: c = 0;
175: for(j=0; j<7; j++){
176: c <<= 1;
177: c |= blk[8*i+j];
178: }
179: iobuf[i] = c;
180: }
181: iobuf[i] = 0;
182: return(iobuf);
183: }
184: enblknot(blk,crp)
185: char *blk;
186: char *crp; {
187: register int i,j;
188: char c;
189: for(i=0;i<70;i++)blk[i] = 0;
190: for(i=0; (c= *crp) && i<64; crp++){
191: if(c>'Z') c -= 6;
192: if(c>'9') c -= 7;
193: c -= '.';
194: for(j=0; j<6; j++, i++)
195: blk[i] = (c>>(5-j)) & 01;
196: }
197: }
198: char *deblknot(blk)
199: char *blk; {
200: register int i,j;
201: char c;
202: static char iobuf[30];
203: for(i=0; i<11; i++){
204: c = 0;
205: for(j=0; j<6; j++){
206: c <<= 1;
207: c |= blk[6*i+j];
208: }
209: c += '.';
210: if(c > '9')c += 7;
211: if(c > 'Z')c += 6;
212: iobuf[i] = c;
213: }
214: iobuf[i] = 0;
215: return(iobuf);
216: }
217: /*
218: * This program implements the
219: * Proposed Federal Information Processing
220: * Data Encryption Standard.
221: * See Federal Register, March 17, 1975 (40FR12134)
222: */
223:
224: /*
225: * Initial permutation,
226: */
227: static char IP[] = {
228: 58,50,42,34,26,18,10, 2,
229: 60,52,44,36,28,20,12, 4,
230: 62,54,46,38,30,22,14, 6,
231: 64,56,48,40,32,24,16, 8,
232: 57,49,41,33,25,17, 9, 1,
233: 59,51,43,35,27,19,11, 3,
234: 61,53,45,37,29,21,13, 5,
235: 63,55,47,39,31,23,15, 7,
236: };
237:
238: /*
239: * Final permutation, FP = IP^(-1)
240: */
241: static char FP[] = {
242: 40, 8,48,16,56,24,64,32,
243: 39, 7,47,15,55,23,63,31,
244: 38, 6,46,14,54,22,62,30,
245: 37, 5,45,13,53,21,61,29,
246: 36, 4,44,12,52,20,60,28,
247: 35, 3,43,11,51,19,59,27,
248: 34, 2,42,10,50,18,58,26,
249: 33, 1,41, 9,49,17,57,25,
250: };
251:
252: /*
253: * Permuted-choice 1 from the key bits
254: * to yield C and D.
255: * Note that bits 8,16... are left out:
256: * They are intended for a parity check.
257: */
258: static char PC1_C[] = {
259: 57,49,41,33,25,17, 9,
260: 1,58,50,42,34,26,18,
261: 10, 2,59,51,43,35,27,
262: 19,11, 3,60,52,44,36,
263: };
264:
265: static char PC1_D[] = {
266: 63,55,47,39,31,23,15,
267: 7,62,54,46,38,30,22,
268: 14, 6,61,53,45,37,29,
269: 21,13, 5,28,20,12, 4,
270: };
271:
272: /*
273: * Sequence of shifts used for the key schedule.
274: */
275: static char shifts[] = {
276: 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1,
277: };
278:
279: /*
280: * Permuted-choice 2, to pick out the bits from
281: * the CD array that generate the key schedule.
282: */
283: static char PC2_C[] = {
284: 14,17,11,24, 1, 5,
285: 3,28,15, 6,21,10,
286: 23,19,12, 4,26, 8,
287: 16, 7,27,20,13, 2,
288: };
289:
290: static char PC2_D[] = {
291: 41,52,31,37,47,55,
292: 30,40,51,45,33,48,
293: 44,49,39,56,34,53,
294: 46,42,50,36,29,32,
295: };
296:
297: /*
298: * The C and D arrays used to calculate the key schedule.
299: */
300:
301: static char C[28];
302: static char D[28];
303: /*
304: * The key schedule.
305: * Generated from the key.
306: */
307: static char KS[16][48];
308:
309: /*
310: * Set up the key schedule from the key.
311: */
312:
313: nbssetkey(key)
314: char *key;
315: {
316: register i, j, k;
317: int t;
318:
319: /*
320: * First, generate C and D by permuting
321: * the key. The low order bit of each
322: * 8-bit char is not used, so C and D are only 28
323: * bits apiece.
324: */
325: for (i=0; i<28; i++) {
326: C[i] = key[PC1_C[i]-1];
327: D[i] = key[PC1_D[i]-1];
328: }
329: /*
330: * To generate Ki, rotate C and D according
331: * to schedule and pick up a permutation
332: * using PC2.
333: */
334: for (i=0; i<16; i++) {
335: /*
336: * rotate.
337: */
338: for (k=0; k<shifts[i]; k++) {
339: t = C[0];
340: for (j=0; j<28-1; j++)
341: C[j] = C[j+1];
342: C[27] = t;
343: t = D[0];
344: for (j=0; j<28-1; j++)
345: D[j] = D[j+1];
346: D[27] = t;
347: }
348: /*
349: * get Ki. Note C and D are concatenated.
350: */
351: for (j=0; j<24; j++) {
352: KS[i][j] = C[PC2_C[j]-1];
353: KS[i][j+24] = D[PC2_D[j]-28-1];
354: }
355: }
356: }
357:
358: /*
359: * The E bit-selection table.
360: */
361: static char e[] = {
362: 32, 1, 2, 3, 4, 5,
363: 4, 5, 6, 7, 8, 9,
364: 8, 9,10,11,12,13,
365: 12,13,14,15,16,17,
366: 16,17,18,19,20,21,
367: 20,21,22,23,24,25,
368: 24,25,26,27,28,29,
369: 28,29,30,31,32, 1,
370: };
371:
372: /*
373: * The 8 selection functions.
374: * For some reason, they give a 0-origin
375: * index, unlike everything else.
376: */
377: static char S[8][64] = {
378: 14, 4,13, 1, 2,15,11, 8, 3,10, 6,12, 5, 9, 0, 7,
379: 0,15, 7, 4,14, 2,13, 1,10, 6,12,11, 9, 5, 3, 8,
380: 4, 1,14, 8,13, 6, 2,11,15,12, 9, 7, 3,10, 5, 0,
381: 15,12, 8, 2, 4, 9, 1, 7, 5,11, 3,14,10, 0, 6,13,
382:
383: 15, 1, 8,14, 6,11, 3, 4, 9, 7, 2,13,12, 0, 5,10,
384: 3,13, 4, 7,15, 2, 8,14,12, 0, 1,10, 6, 9,11, 5,
385: 0,14, 7,11,10, 4,13, 1, 5, 8,12, 6, 9, 3, 2,15,
386: 13, 8,10, 1, 3,15, 4, 2,11, 6, 7,12, 0, 5,14, 9,
387:
388: 10, 0, 9,14, 6, 3,15, 5, 1,13,12, 7,11, 4, 2, 8,
389: 13, 7, 0, 9, 3, 4, 6,10, 2, 8, 5,14,12,11,15, 1,
390: 13, 6, 4, 9, 8,15, 3, 0,11, 1, 2,12, 5,10,14, 7,
391: 1,10,13, 0, 6, 9, 8, 7, 4,15,14, 3,11, 5, 2,12,
392:
393: 7,13,14, 3, 0, 6, 9,10, 1, 2, 8, 5,11,12, 4,15,
394: 13, 8,11, 5, 6,15, 0, 3, 4, 7, 2,12, 1,10,14, 9,
395: 10, 6, 9, 0,12,11, 7,13,15, 1, 3,14, 5, 2, 8, 4,
396: 3,15, 0, 6,10, 1,13, 8, 9, 4, 5,11,12, 7, 2,14,
397:
398: 2,12, 4, 1, 7,10,11, 6, 8, 5, 3,15,13, 0,14, 9,
399: 14,11, 2,12, 4, 7,13, 1, 5, 0,15,10, 3, 9, 8, 6,
400: 4, 2, 1,11,10,13, 7, 8,15, 9,12, 5, 6, 3, 0,14,
401: 11, 8,12, 7, 1,14, 2,13, 6,15, 0, 9,10, 4, 5, 3,
402:
403: 12, 1,10,15, 9, 2, 6, 8, 0,13, 3, 4,14, 7, 5,11,
404: 10,15, 4, 2, 7,12, 9, 5, 6, 1,13,14, 0,11, 3, 8,
405: 9,14,15, 5, 2, 8,12, 3, 7, 0, 4,10, 1,13,11, 6,
406: 4, 3, 2,12, 9, 5,15,10,11,14, 1, 7, 6, 0, 8,13,
407:
408: 4,11, 2,14,15, 0, 8,13, 3,12, 9, 7, 5,10, 6, 1,
409: 13, 0,11, 7, 4, 9, 1,10,14, 3, 5,12, 2,15, 8, 6,
410: 1, 4,11,13,12, 3, 7,14,10,15, 6, 8, 0, 5, 9, 2,
411: 6,11,13, 8, 1, 4,10, 7, 9, 5, 0,15,14, 2, 3,12,
412:
413: 13, 2, 8, 4, 6,15,11, 1,10, 9, 3,14, 5, 0,12, 7,
414: 1,15,13, 8,10, 3, 7, 4,12, 5, 6,11, 0,14, 9, 2,
415: 7,11, 4, 1, 9,12,14, 2, 0, 6,10,13,15, 3, 5, 8,
416: 2, 1,14, 7, 4,10, 8,13,15,12, 9, 0, 3, 5, 6,11,
417: };
418:
419: /*
420: * P is a permutation on the selected combination
421: * of the current L and key.
422: */
423: static char P[] = {
424: 16, 7,20,21,
425: 29,12,28,17,
426: 1,15,23,26,
427: 5,18,31,10,
428: 2, 8,24,14,
429: 32,27, 3, 9,
430: 19,13,30, 6,
431: 22,11, 4,25,
432: };
433:
434: /*
435: * The current block, divided into 2 halves.
436: */
437: static char L[32], R[32];
438: static char tempL[32];
439: static char f[32];
440:
441: /*
442: * The combination of the key and the input, before selection.
443: */
444: static char preS[48];
445:
446: /*
447: * The payoff: encrypt a block.
448: */
449:
450: blkencrypt(block, edflag)
451: char *block;
452: {
453: int i, ii;
454: register t, j, k;
455:
456: /*
457: * First, permute the bits in the input
458: */
459: for (j=0; j<64; j++)
460: L[j] = block[IP[j]-1];
461: /*
462: * Perform an encryption operation 16 times.
463: */
464: for (ii=0; ii<16; ii++) {
465: /*
466: * Set direction
467: */
468: if (edflag)
469: i = 15-ii;
470: else
471: i = ii;
472: /*
473: * Save the R array,
474: * which will be the new L.
475: */
476: for (j=0; j<32; j++)
477: tempL[j] = R[j];
478: /*
479: * Expand R to 48 bits using the E selector;
480: * exclusive-or with the current key bits.
481: */
482: for (j=0; j<48; j++)
483: preS[j] = R[E[j]-1] ^ KS[i][j];
484: /*
485: * The pre-select bits are now considered
486: * in 8 groups of 6 bits each.
487: * The 8 selection functions map these
488: * 6-bit quantities into 4-bit quantities
489: * and the results permuted
490: * to make an f(R, K).
491: * The indexing into the selection functions
492: * is peculiar; it could be simplified by
493: * rewriting the tables.
494: */
495: for (j=0; j<8; j++) {
496: t = 6*j;
497: k = S[j][(preS[t+0]<<5)+
498: (preS[t+1]<<3)+
499: (preS[t+2]<<2)+
500: (preS[t+3]<<1)+
501: (preS[t+4]<<0)+
502: (preS[t+5]<<4)];
503: t = 4*j;
504: f[t+0] = (k>>3)&01;
505: f[t+1] = (k>>2)&01;
506: f[t+2] = (k>>1)&01;
507: f[t+3] = (k>>0)&01;
508: }
509: /*
510: * The new R is L ^ f(R, K).
511: * The f here has to be permuted first, though.
512: */
513: for (j=0; j<32; j++)
514: R[j] = L[j] ^ f[P[j]-1];
515: /*
516: * Finally, the new L (the original R)
517: * is copied back.
518: */
519: for (j=0; j<32; j++)
520: L[j] = tempL[j];
521: }
522: /*
523: * The output L and R are reversed.
524: */
525: for (j=0; j<32; j++) {
526: t = L[j];
527: L[j] = R[j];
528: R[j] = t;
529: }
530: /*
531: * The final output
532: * gets the inverse permutation of the very original.
533: */
534: for (j=0; j<64; j++)
535: block[j] = L[FP[j]-1];
536: }
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