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Displaying  Source Code(s)  
 

 
encryption and decryption of files

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Description : usally for encryption and ecryption the software being used will be associate with password by which an un-authorized user with that same software can decrypt, so in this program evelope by me with new algorithm for encryption an ecryption in which password is associated with encrypted file which provides security from un-authorized users of that encrypted file.there will come two extra unreable characters at the end of decrypted file which indicates decryption of entire file.

In main function we declare required variable.

printf(" enter choice

1)encode
2)view ecoded file
3)
decode
4)view decoced file
5)exit ------");
// this is to print the main menu
scanf("%d",&ch); // entering
of choice
while(ch!=5) // until
choice is exit
{
if(ch==1) //if
choice is to encrypt
{
scanf("%s",name); // accept file
name
scanf("%c",&ff); //accept the
choice of change

// the file position or not
if(ff=='c'||ff=='C')
{strcpy(encri,ruf);scanf("%s",encri);} // so as to change enter file path

cscanf("%s",pass); // enter
password
l=strlen(pass); // l
=string length of password

st=fopen(name,"r"); // open the
file to be encrypted
ed=fopen(encri,"w"); // open the file
to where to be
//
encrypted
while(!feof(st)) // until end
of file to be encrypted
{ x=fgetc(st); // read each
character into X
fputc(x+pass[i++%l],ed); // write the sum of X
and password
} //
char
fclose(st); // close first
file
fclose(ed); // close second file
}
if(ch==3) // if choice is
decryption
{
scanf(%s,encri); //enter the file name
to be decrypted
ed=fopen(encri,"r"); //open the above mentioned
file
scanf("%c",&ff); //accept the choice of
change
// the file
position or not

if(ff=='c'||ff=='C')
{ strcpy(decri,ruf);
scanf("%s",decri); // so as to change enter file path
}
cscanf("%s",pass); // enter password
de=fopen(decri,"w"); //open a file to store decoded
data
while(!feof(ed)) // until end of file to be
encrypted
{
x=fgetc(ed); // read each character
into X
fputc(x-pass[i++%l],de); // write the sum of X and password
} // char


fclose(ed); // close first file
fclose(de); // close second file
}

if(ch==2) //if choice is to view the
contents encoded file
{
ed=fopen(encri,"r"); //open that file and read each
character
while(!feof(ed))
printf("%c",fgetc(ed)); //print them until end of file
fclose(ed); // close this file
}
if(ch==4) //if choice is to view the
contents decoded file
{
ed=fopen(decri,"r"); //open that file and read each
character
while(!feof(ed))
printf("%c",fgetc(ed)) ; //print them until end of file
fclose(ed) ; // close this file
}

scanf("%d",&ch); // enter the choice from menu
} // end while
} // end main

 

 

 

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