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Symetric-key encryption program using a key file + a hard-coded key (so to decrypt you need the key + the binary of the program used to crypt)
/*
* Copyright (C) 2006, 2007 Sarzyniec Luc <mail@olbat.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* see the COPYING file for more informations */
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <signal.h>
#include <malloc.h>
#include <stdio.h>
/* The software use a unique binary key to crypt files, it is better to use a
* long key -more than 512 bytes.
* You can use the printfile program on /dev/random to generate one -you can
* download it at http://xiato.net/svn/dev/misc/
*/
#define KEY_SOFT __extension__ \
"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12"\
"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13"\
"\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14"\
"\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15"\
"\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16"\
"\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17"\
"\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18"\
"\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19"\
#define BUFFER_DEFAULT_SIZE 4096
/* This software could be easy to hack because the size of the crypted file,
* so the size of the original file is known
*/
int main(int argc, char **argv)
{
if (argc > 1)
{
int fd, keyptr;
char buffer_file[BUFFER_DEFAULT_SIZE];
char *buffer_key;
unsigned char keyc;
ssize_t len,tmplen,size_key;
if (argc > 2)
{
struct stat st;
int fd_key,len_key;
stat(*(argv + 2),&st);
size_key = st.st_size;
buffer_key = (char *) malloc(size_key*sizeof(char));
fd_key = open(*(argv + 2), O_RDONLY);
len_key = 0;
while(((len = read(fd_key,(buffer_key + len_key),
size_key)) > 0)
&& ((len_key += len) < size_key));
close(fd_key);
}
else
{
char *tmpbuff;
buffer_key = tmpbuff = (char *)
malloc(sizeof(char) * BUFFER_DEFAULT_SIZE);
while ((read(0,tmpbuff,1) > 0) && (*tmpbuff++ != '\n')
&&(tmpbuff < (buffer_key+BUFFER_DEFAULT_SIZE)));
size_key = (tmpbuff - buffer_key);
}
fd = open(*(argv + 1), O_RDONLY);
keyptr = 0;
keyc = *buffer_key;
/* reading of "keyc" bytes affects the value of len
* so the value of tmplen which is used to get a byte in
* KEY_SOFT
*/
while ((len = read(fd,buffer_file,keyc)) > 0)
{
tmplen = len;
while (tmplen--)
{
keyc = *(buffer_key +
(keyptr++ % size_key));
/* using keyc, tmplen and keyptr values to get
* better results when using a very short key
*/
buffer_file[tmplen] ^=
(keyc ^ KEY_SOFT[(keyc*tmplen+keyptr)
% sizeof(KEY_SOFT)]
);
}
write(1,&buffer_file,len);
}
free(buffer_key);
close(fd);
}
else
{
printf( "usage: %s <file to crypt> [<key file>]\n"
"\texample: %s file.txt file.key > file.crypt\n"
"\tthen: %s file.crypt file.key > file.txt\n"
,*argv,*argv,*argv);
}
return 0;
}
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