Created
September 19, 2011 12:08
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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)
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/* | |
* 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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