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Title Encryption and Decryption of file wat so ever
Author Rahul
Author Email rahul_aurora_it [at] yahoo.co.in
Description The following C code can encrypt any sort of file be it be a sound,image,video or etc

Category C » Beginners / Lab Assignments
Hits 321153
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/* A simulated C program to encrypt or decrypt a file with L=26, K=3 and Buffer Stream Divisions=2 as per described approach */ /* Few Notations used R-Read W-write */ #include<stdio.h> #include<conio.h> #include<process.h> #include"fcntl.h" #include"types.h" #include"stat.h" #include<io.h> #include<ctype.h> #include<time.h> #include<stdlib.h> /*Procedure to copy a buffer stream content to another unsigned char *strcp(unsigned char buf[],unsigned char l[],unsigned int byt) { for(int i=0;i<byt;i++) buf[i]=l[i]; buf[i]=0; return(buf); } /*Procedure To reverse buffer stream content*/ unsigned char *strrever(unsigned char buf[],unsigned int byt) { unsigned char l[1024]; for(int i=byt-1;i>=0;i--) l[i]=buf[i]; l[i]=0; for(i=0;i<byt;i++) buf[i]=l[i]; buf[i]=0; return(buf); } /* Procedure Jumble Buffer stream content*/ unsigned char *strjab(unsigned char buf[],unsigned int byt,unsigned char parts,unsigned char comb) { unsigned char k[1024],l[1024],x[1024],y[1024]; int hlen,i,j,len,n=0; if(parts==2&&comb==2) { len=byt; hlen=len/2; for(i=0;i<hlen;i++) k[i]=buf[i]; k[i]=0; j=i; for(i=hlen;i<len;i++) {l[n]=buf[i];n++;} l[n]=0; for(i=0;i<j;i++) l[n+i]=k[i]; l[n+i]=0; for(i=0;i<len;i++) buf[i]=l[i]; buf[i]=0; } else if(parts==4) { } strrever(buf,byt); return(buf); } /* A procedure to Encrypt a given file of any format taking parameter name of the as parameter. */ int encrypt(unsigned char *p) { unsigned char buf[1024]; // buf is a buffer where data of file is R/W int in,out,i; /* 'in' is a handle to a file which is for R a file 'out' is a handle to a file which is for W a file, 'i' is a counter */ unsigned int byt; z:in=open(p,O_RDONLY|O_BINARY); // Opening given file in R mode out=open("",O_CREAT|O_BINARY|O_WRONLY,S_IWRITE); // Opening a temp file in W mode if(in==-1) { return(0); // if file doesn't exist it quits } while(1) { byt=read(in,buf,1024); /* The os starts fetching data from the file and fills it in the buffer*/ for(i=0;i<byt;i++) // looping the buffer { _BL=buf[i]; asm neg bl; _CL=0x04; asm ror bl,cl; _BL=_BL+0x1B0; buf[i]=_BL; /* Encryption logic is applied and a single byte is encrypted */ asm xor bl,bl; } if(byt>0) // If file is not empty it goes to next statement { write(out,buf,byt); // The buffer values are written in temp file } else // If file is now empty then it is quits the loop break; } close(in); // Closing the given file close(out); // Closing the temp file in=open("",O_RDONLY|O_BINARY); // Opening Temp file in R mode out=open(p,O_CREAT|O_BINARY|O_WRONLY,S_IWRITE); // Opening given file in W mode if(in==-1) //If resource file gets deleted by an attack by an other process { close(in); close(out); // The process restarts goto z; } while(1) { byt=read(in,buf,1024); // R content of Temp file strjab(buf,byt,2,2); if(byt>0) write(out,buf,byt); // W content to Given file else break; } close(in); // Closing the Temp file close(out); // Closing the Given file remove(""); // Deleting the temp file strcp(buf," "); //Corrupting the present Buffer value return(1); } /* A procedure to Decrypt a given file of any format taking parameter name of the as parameter. */ int decrypt(unsigned char *p) { unsigned char buf[1024]; // buf is a buffer where data of file is R/W int in,out,i; /* 'in' is a handle to a file which is for R a file 'out' is a handle to a file which is for W a file, 'i' is a counter */ unsigned int byt; l:in=open(p,O_RDONLY|O_BINARY); // Opening given file in R mode out=open("",O_CREAT|O_BINARY|O_WRONLY,S_IWRITE); // Opening a temp file in W mode if(in==-1) // if file doesn't exist it quits { return(0); } while(1) { byt=read(in,buf,1024); // R content of Given file for(i=0;i < byt;i++) { _BL=buf[i]; _BL=_BL-0x1B0; _CL=0x04; asm rol bl,cl; // Decrypting logic for Decrypting a Single byte asm neg bl; buf[i]=_BL; asm xor bl,bl; } if(byt>0) { write(out,buf,byt); //W into Temp file } else break; } close(in); close(out); in=open("",O_RDONLY|O_BINARY); // Opening Temp file in R mode out=open(p,O_CREAT|O_BINARY|O_WRONLY,S_IWRITE); // Opening Given file in W mode if(in==-1) { close(in); close(out); goto l; } while(1) { byt=read(in,buf,1024); strjab(buf,byt,2,2); //Jumbling the buffer stream if(byt>0) write(out,buf,byt); // W into Given file else break; } close(in); close(out); remove(""); // Deleting Temp file strcp(buf," "); // Corrupting the buffer return(1); } /* The Main Function to execute the program */ int main(int argc,char *argv[]) { clock_t start, end; argc=argc&argc; argc=14; if(strcmp(argv[1],"")==0) //If No File or No Input is specified { clrscr(); textcolor(14); // User Help Screen when no input is dragged cprintf(" DRAG AN INPUT FILE TOWARDS THIS ICON"); textcolor(RED); cputs(" DO LOCKING OR UNLOCKING BY TYPING L OR U"); textcolor(GREEN); cputs(" IF U FRIST LOCK A FILE THEN UNLOCK IT FOR RETRIEVAL AND VICE-VERSA"); _setcursortype(_NOCURSOR); getch(); return(0); } else { char c; clrscr(); // User input Screen if they drag a file x:printf(" U WANT LOCK OR UNLOCK THE FILE (L/U):"); /* If u press L or l for the first time, then for retrieval press U or u and vice versa.. The if u r were pressing L or l for 'N' times without pressing U or u then for retrieval pressing U or u 'N' times */ _setcursortype(_SOLIDCURSOR); c=getchar(); //Giving the input whether to lock or unlock by pressing 'L' or 'U' (or) 'l' or 'u' if(c=='L' || c=='l') //Procedure for locking { printf(" Locking...."); _setcursortype(_NOCURSOR); start = clock(); //Starting the clock counter encrypt(argv[1]); end = clock(); // Stopping the clock counter printf(" The time was: %f ", (end - start) / CLK_TCK); } else if(c=='U' || c=='u') //Procedure for unlocking { printf(" Unlocking....."); _setcursortype(_NOCURSOR); start=clock(); //Starting the clock counter decrypt(argv[1]); end= clock(); // Stopping the clock counter printf(" The time was: %f ",(end - start) / CLK_TCK); } else { printf(" wrong i/p,please press a key as per given i/p's "); _setcursortype(_NOCURSOR); getch(); clrscr(); goto x; } } return(1); }

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