/*-
 *      "enigma.c" is in file cbw.tar from
 *      anonymous FTP host watmsg.waterloo.edu: pub/crypt/cbw.tar.Z
 *
 *      A one-rotor machine designed along the lines of Enigma
 *      but considerably trivialized.
 *
 *      A public-domain replacement for the UNIX "crypt" command.
 *
 *      Upgraded to function properly on 64-bit machines.
 */

#include <sys/types.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MINUSKVAR "CrYpTkEy"

#define ROTORSZ 256
#define MASK 0377
static char     t1[ROTORSZ];
static char     t2[ROTORSZ];
static char     t3[ROTORSZ];
static char     deck[ROTORSZ];
static char     buf[13];

static void     shuffle(char *);
static void     setup(char *);

static void
setup(char *pw)
{
        int ic, i, k, temp;
        char salt[3];
        unsigned rnd;
        int32_t seed;
        char *cryptpw;

        if (crypt_set_format("des") == 0) {
                fprintf(stderr, "crypt_set_format(\"des\") failed.\n");
                exit(1);
        }

        strlcpy(salt, pw, sizeof(salt));
        cryptpw = crypt(pw, salt);
        if (cryptpw == NULL) {
                fprintf(stderr, "crypt(3) failure\n");
                exit(1);
        }
        memcpy(buf, cryptpw, sizeof(buf));
        seed = 123;
        for (i=0; i<13; i++)
                seed = seed*buf[i] + i;
        for(i=0;i<ROTORSZ;i++) {
                t1[i] = i;
                deck[i] = i;
        }
        for(i=0;i<ROTORSZ;i++) {
                seed = 5*seed + buf[i%13];
                rnd = seed % 65521;
                k = ROTORSZ-1 - i;
                ic = (rnd&MASK)%(k+1);
                rnd >>= 8;
                temp = t1[k];
                t1[k] = t1[ic];
                t1[ic] = temp;
                if(t3[k]!=0) continue;
                ic = (rnd&MASK) % k;
                while(t3[ic]!=0) ic = (ic+1) % k;
                t3[k] = ic;
                t3[ic] = k;
        }
        for(i=0;i<ROTORSZ;i++)
                t2[t1[i]&MASK] = i;
}

int
main(int argc, char *argv[])
{
        int i, n1, n2, nr1, nr2;
        int secureflg = 0, kflag = 0;
        char *cp;

        if (argc > 1 && argv[1][0] == '-') {
                if (argv[1][1] == 's') {
                        argc--;
                        argv++;
                        secureflg = 1;
                } else if (argv[1][1] == 'k') {
                        argc--;
                        argv++;
                        kflag = 1;
                }
        }
        if (kflag) {
                if ((cp = getenv(MINUSKVAR)) == NULL) {
                        fprintf(stderr, "%s not set\n", MINUSKVAR);
                        exit(1);
                }
                setup(cp);
        } else if (argc != 2) {
                setup(getpass("Enter key:"));
        }
        else
                setup(argv[1]);
        n1 = 0;
        n2 = 0;
        nr2 = 0;

        while((i=getchar()) != -1) {
                if (secureflg) {
                        nr1 = deck[n1]&MASK;
                        nr2 = deck[nr1]&MASK;
                } else {
                        nr1 = n1;
                }
                i = t2[(t3[(t1[(i+nr1)&MASK]+nr2)&MASK]-nr2)&MASK]-nr1;
                putchar(i);
                n1++;
                if(n1==ROTORSZ) {
                        n1 = 0;
                        n2++;
                        if(n2==ROTORSZ) n2 = 0;
                        if (secureflg) {
                                shuffle(deck);
                        } else {
                                nr2 = n2;
                        }
                }
        }

        return 0;
}

static void
shuffle(char deckary[])
{
        int i, ic, k, temp;
        unsigned rnd;
        static int32_t seed = 123;

        for(i=0;i<ROTORSZ;i++) {
                seed = 5*seed + buf[i%13];
                rnd = seed % 65521;
                k = ROTORSZ-1 - i;
                ic = (rnd&MASK)%(k+1);
                temp = deckary[k];
                deckary[k] = deckary[ic];
                deckary[ic] = temp;
        }
}