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Annotation of 3BSD/cmd/net/nbs.c, revision 1.1

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

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