Title	ENCRYPTION & DECRYPTION OF FILE(CRYPTOGRAPHY)
Author:	MURALI KUMAR .P Visitor Submitted Source Code
Author Email:	murali_ece2003@yahoo.co.in
Description:	The encryption program converts a DAT file into BMP file with a password.Then decryption is done by adding e wtih bmp file name and opened with password.The decrypted file can be found using(func)type defilename. D:\dosbased\TURBOC>encrypt enter file name to encrypt test.dat enter password[ space to end ] ****** D:\dosbased\TURBOC>decrypt enter file name to decrypt etest.bmp enter password[ space to end ] ****** D:\dosbased\TURBOC>type test.dat The dawn of a new PC era. The first 64-bit processor -G5. D:\dosbased\TURBOC>type detest.dat The dawn of a new PC era. The first 64-bit processor -G5. D:\dosbased\TURBOC> Encrypted file: etest.bmp
Hits:	4847 Since 25th November, 2003
Code:	Select and Copy the Code /* Encryption Program */ #include<stdio.h> #include<string.h> char map1[]= "aeiostbcdfghjklmnpqruvwxyz0123456789AEIOSTBCDFGHJKLMNPQRUVWXYZ "; char map2[]= "otsiaehfbdgclnjkmuypzqvwxr4697081325OTSIAEHFBDGCLNJKMUYPZQVWXR "; void main() { char fn[20],m1,m2,tfn[20],p1[10]; FILE *f1,*f2; int i=0,j=0,flag=0,l,a,k; printf("\nenter file name to encrypt\n"); scanf("%s",fn); f1=fopen(fn,"r");/* OPENS SOURCE FILE */ if(f1==NULL){ printf("\ncannot open file"); exit(0); } printf("\nenter password[ space to end ]\n"); while((int)(m1=getch())!=32) { printf("*"); p1[i]=m1; i++; } p1[i]='\0'; i=0; tfn[i]='e'; m1=fn[0]; while(m1!='.')/* CONVERTS EXTESION .DAT TO .BMP */ { tfn[i+1]=fn[i]; i++; m1=fn[i]; } tfn[i]='.';tfn[i+1]='b';tfn[i+2]='m';tfn[i+3]='p'; i=0; f2=fopen(tfn,"wb");/* OPENS DESTINATION FILE */ if(f2==NULL) { printf("\ncannot open file"); exit(0); } m1=getc(f1); while(!feof(f1)) { for(i=0;i<63;i++)/* LAYER ONE */ { flag=0; if(m1==map1[i]) { m2=map2[i]; flag=1; break; } } if(flag==0) m2=m1;/* END OF LAYER ONE */ l=strlen(p1); m2=(m2)^(~p1[j]);/* LAYER TWO */ for(i=7;i>=0;i--)/* LAYER THREE */ { a=1<<i; k=(int)m2&a; if(k==0) putc(0,f2);//WRITES CHAR IN BMP FILLE else { k=1; putc(1,f2); }//WRITES CHAR IN BMP FILE } j++; if(j==l) j=0; m1=getc(f1); } } /* Decryption Program */ #include<stdio.h> #include<string.h> #include<math.h> char map1[]= "aeiostbcdfghjklmnpqruvwxyz0123456789AEIOSTBCDFGHJKLMNPQRUVWXYZ "; char map2[]= "otsiaehfbdgclnjkmuypzqvwxr4697081325OTSIAEHFBDGCLNJKMUYPZQVWXR "; void main() { char fn[20],m1,m2,tfn[20],p1[10]; FILE *f1,*f2; int i=0,j=0,flag=0,l,k,c,w=0; printf("\nenter file name to decrypt\n"); scanf("%s",fn); f1=fopen(fn,"rb");/* OPENS ENCRYPTED .BMP FILE */ if(f1==NULL) { printf("\ncannot open file"); exit(0); } printf("\nenter password[ space to end ]\n"); while((int)(m1=getch())!=32) { printf("*"); p1[i]=m1; i++; } p1[i]='\0'; l=strlen(p1); i=0; tfn[i]='d'; m1=fn[0]; while(m1!='.')/* CONVERTS .BMP EXTENSION TO .DAT */ { tfn[i+1]=fn[i]; i++; m1=fn[i]; } tfn[i+1]='.';tfn[i+2]='d';tfn[i+3]='a';tfn[i+4]='t'; i=0; f2=fopen(tfn,"w");//OPENS OUTPUT FILE if(f2==NULL) { printf("\ncannot open file"); exit(0); } while(!feof(f1)) { w=0; for(k=7;k>=0;k--)/* LAYER ONE */ { c=getc(f1); w+=pow(2,k)*(int)c; } m2=(char)w;/* END OF LAYER ONE */ m2=(m2)^(~p1[j]);/* LAYER TWO */ j++; if(j==l) j=0; for(i=0;i<63;i++)/* LAYER THREE */ { flag=0; if(m2==map2[i]) { m1=map1[i]; flag=1; break; } } if(flag==0) m1=m2; putc(m1,f2);// WRITES CHARACTER TO OUTPUT FILE } }