/*SOME FACTS WORTH KNOWING*/ /*long max is 2147483647, unsigned long max is 4294967295, (97^5)/2 is 4293670128.5 */ /*sample time(0)=2937060310 seconds since 1/1/1970, (long)time(0)=-1357906986*/ #include #include #include /*RANDOM NUMBER GENERATOR*/ #define MODMULT(a,b,c,m,s) q=s/a; s=b*(s-a*q)-c*q; if(s<0)s+=m; void unscatind(int rlistbuf[], int rlistscat[], int kicklist[], int n); void set_globals_plus(int xmask[]); void decrypt(int rlistbuffer[], char buffer[],int rlistcypher[]); double runup(int xrun); double combine_lcg(void); void init_lcg(long init_s1, long init_s2); int getfilename(char *a); void wildseeds(long *seed1, long *seed2, int r_seeds97[]); int getcypher50(int rcypher[], FILE *fc, int cmask[]); int count=1; long s1=1, s2=1; int loc_seeds_kicked[10]; int loc_text_kicked[40]; /*KEY IS STUFF BETWEEN LINES. MUST BE THE SAME AS KEY FOR ENCRYPTION*/ /*-------------------------------------------------------------------------*/ #define M1_COUNT 87831L /* -50,000 < M1_COUNT < 250,000 */ #define M2_COUNT 126543L /* -50,000 < M2_COUNT < 250,000 */ #define A1_COUNT 78785L /* -.25x10^9 < A1_COUNT < 10^9 */ #define A2_COUNT -89897L /* -.25x10^9 < A2_COUNT < 10^9 */ char p_alphabet[97]={49,113,97,122,50,119,115,120,51,101,100,99,52,114,102,\ 118,53,116,103,98,54,121,104,110,55,117,106,109,56,105,107,44,57,111,108,46,\ 48,112,59,47,45,91,39,61,93,92,96,33,81,65,90,64,87,83,88,35,69,68,67,36,82,70\ ,86,37,84,71,66,94,89,72,78,38,85,74,77,42,73,75,60,40,79,76,62,41,80,58,63,95,\ 123,34,43,125,124,126,32,9,10}; char c_alphabet[97]={113,97,122,50,119,115,120,51,101,100,99,52,114,102,118,53,\ 116,103,98,54,121,104,110,55,117,106,109,56,105,107,44,57,111,108,46,48,112,59,\ 47,45,91,39,61,93,92,96,33,81,65,90,64,87,83,88,35,69,68,67,36,82,70,86,37,84,71,\ 66,94,89,72,78,38,85,74,77,42,73,75,60,40,79,76,62,41,80,58,63,95,123,34,43,125,\ 124,126,49,32,9,10}; int keyperm50[50]={41,4,21,33,17,37,2,32,14,30,0,15,36,1,44,34,3,48,12,25,16,27,\ 42,45,29,22,49,31,47,40,8,43,5,19,23,6,10,28,18,46,35,11,20,7,39,24,9,38,13,26}; int runupseeds[10]={56,34,91,13,33,66,43,29,71,10}; int runuptext[40]={6,3,9,3,3,6,3,9,7,1,9,4,5,6,1,8,2,5,2,2,\ 4,4,2,3,7,3,2,3,4,3,10,3,1,4,3,3,4,10,5,4}; int scatterseed[10]={51,44,61,11,39,27,51,19,34,8}; /*-------------------------------------------------------------------------*/ /*IN main() WE GET 50+ CHARACTERS OF CYPHERTEXT CORRESPONDING TO FORTY*/ /*CHARACTERS OF PLAINTEXT. THE ARRAY c_alphabet IS USED TO PUT THIS INTO ASCI*/ main() { /*BASIC DECLARATIONS AND SETUP*/ int i, j, count, cmask[127]; char ch, plainfile[20], cypherfile[20]; int rplainline[40]={0}, rcypherline[50]={0}; char plainline[40]={0}; FILE *fp, *fc; set_globals_plus(cmask); for(i=0; i<10; ++i) loc_seeds_kicked[i]=keyperm50[i]; for(i=0; i<40; ++i) loc_text_kicked[i]=keyperm50[10+i]; /*DESIGNATES CYPHERFILE AND PLAINTEXT FILE FOR DECRYPTION AND OUTPUT*/ printf("\nEnter the name of the cypherfile: "); getfilename(cypherfile); fc=fopen(cypherfile, "r"); printf("\nEnter the name of the plainfile: "); getfilename(plainfile); printf("\n"); fp=fopen(plainfile, "w"); /*GETS LINE OF CYPHERTEXT AND DECRYPTS IT AND WRITES IT TO PLAINTEXT FILE*/ do{ j=getcypher50(rcypherline, fc, cmask); if(j>=50) { decrypt(rplainline, plainline, rcypherline); for(i=0; i<40; ++i) fprintf(fp,"%c", plainline[i]); } /*IF YOU CUT AND PASTE CYPHERTEXT FOR MAILING ETC., THERE ARE TWO COMMON*/ /*ERRORS. ONE IS TO REMOVE THE NEWLINE ON THE LAST LINE OF CYPHERTEXT*/ /*THE OTHER IS TO ADD ADDITIONAL BLANK OR SHORT LINES. THIS IS A BIT*/ /*OF "FAULT-TOLERANCE DETECTION" FOR THESE COMMON ERRORS*/ if(j==80) printf("\nCorrupt cyphertext: last line missing \\n\n"); if(j==0) printf("\nCorrupt cyphertext: extra terminal \\n present\n"); } while(j==50); /*FINAL CLEAN UP AND NOTICE THAT WE ARE DONE*/ fclose(fc); fclose(fp); printf("\nDECRYPTION DONE\n"); } /*END OF main()*/ /*INVERSE FUNCTION OF MAP SPECIFIED BY GLOBAL ARRAY c_alphabet[]*/ void set_globals_plus(int xmask[]) { int i; for(i=0; i<127; ++i)xmask[i]=-1; for(i=0; i<97; ++i) xmask[c_alphabet[i]]=i; } /*HEART OF THE DECRYPTION PROCESS IN THE NEXT TWO FUNCTIONS*/ void decrypt(int rlistbuffer[], char buffer[], int rlistcypher[]) { int i, r_seeds_scat[10], r_seeds97[10], ranscatter[40], scattertext[40]; char ch; long x=0L, y=0L; for(i=0; i<10; ++i) r_seeds_scat[i]=rlistcypher[loc_seeds_kicked[i]]; unscatind(r_seeds97, r_seeds_scat, scatterseed, 10); wildseeds(&x, &y, r_seeds97); init_lcg(x,y); for(i=0; i<40; ++i) ranscatter[i]=97*runup(runuptext[i]); for(i=0; i<40; ++i) scattertext[i]=rlistcypher[loc_text_kicked[i]]; unscatind(rlistbuffer, scattertext, ranscatter, 40); for(i=0; i<40; ++i) buffer[i]= p_alphabet[rlistbuffer[i]]; } void wildseeds(long *seed1, long *seed2, int r_seeds97[]) { int i; long x=0L, y=0L; unsigned long xul, yul; double xd=0.0, yd=0.0; for(i=0; i<5; ++i) xd+=r_seeds97[i]*pow(97,i); for(i=5; i<10; ++i) yd+=r_seeds97[i]*pow(97,(i-5)); xul=xd/2; yul=yd/2; x=xul; y=yul; *seed1=x; *seed2=y; } /*NEXT TWO FUNTIONS PLUS MODMULT DEFINE LCG PROCESS FOR PSEUDORANDOM NUMBERS*/ /*THIS LCG PROCESS DUE TO L'ECUYER IS IN SCHNEIER, APPLIED CRYPTOGRAPHY*/ double combine_lcg(void) { long q, z; MODMULT(53668L, 40014L, 12211L, 2147483563L, s1) MODMULT(52774L, 40629L, 3791L, 2147483562L, s2) z=s1-s2; if(z<1) z+=2147483562L; return z*4.656613e-10; } void init_lcg(long init_s1, long init_s2) { s1=init_s1; s2=init_s2; } /*NEXT TWO FUNCTIONS ARE EXTRA, FOR OUR USE OF THESE LCGs*/ double runup(int xrun) { int i; for(i=-1; i=50) break; else return 0; /*cyphertext line too short*/ } cypherbuffer[i]=c; } j=0; for(i=0; (i<80)&&(cypherbuffer[i]!='\0'); ++i){ if(cypherbuffer[i]=='\\'){ if(cypherbuffer[i+1]=='\\') rcypher[j++]=cmask['\\']; else if(cypherbuffer[i+1]=='n') rcypher[j++]=cmask['\n']; else if(cypherbuffer[i+1]=='t') rcypher[j++]=cmask['\t']; else if(cypherbuffer[i+1]=='s') rcypher[j++]=cmask[' ']; i=i+1; } else rcypher[j++]=cmask[cypherbuffer[i]]; } if(c==EOF) return 80; return j; /* j should be 50 */ }