NAME¶
encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
SYNOPSIS¶
#define _XOPEN_SOURCE /* See
feature_test_macros(7) */
#include <unistd.h>
void encrypt(char block[64], int edflag);
#define _XOPEN_SOURCE /* See
feature_test_macros(7) */
#include <stdlib.h>
void setkey(const char *key);
#define _GNU_SOURCE /* See
feature_test_macros(7) */
#include <crypt.h>
void setkey_r(const char *key, struct crypt_data
*data);
void encrypt_r(char *block, int edflag, struct
crypt_data *data);
Each of these requires linking with
-lcrypt.
DESCRIPTION¶
These functions encrypt and decrypt 64-bit messages. The
setkey()
function sets the key used by
encrypt(). The
key argument used
here is an array of 64 bytes, each of which has numerical value 1 or 0. The
bytes key[n] where n=8*i-1 are ignored, so that the effective key length is 56
bits.
The
encrypt() function modifies the passed buffer, encoding if
edflag is 0, and decoding if 1 is being passed. Like the
key
argument, also
block is a bit vector representation of the actual value
that is encoded. The result is returned in that same vector.
These two functions are not reentrant, that is, the key data is kept in static
storage. The functions
setkey_r() and
encrypt_r() are the
reentrant versions. They use the following structure to hold the key data:
struct crypt_data {
char keysched[16 * 8];
char sb0[32768];
char sb1[32768];
char sb2[32768];
char sb3[32768];
char crypt_3_buf[14];
char current_salt[2];
long int current_saltbits;
int direction;
int initialized;
};
Before calling
setkey_r() set
data->initialized to zero.
RETURN VALUE¶
These functions do not return any value.
ERRORS¶
Set
errno to zero before calling the above functions. On success, it is
unchanged.
- ENOSYS
- The function is not provided. (For example because of former USA export
restrictions.)
ATTRIBUTES¶
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
encrypt (), setkey () |
Thread safety |
MT-Unsafe race:crypt |
encrypt_r (), setkey_r () |
Thread safety |
MT-Safe |
encrypt(),
setkey(): POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
The functions
encrypt_r() and
setkey_r() are GNU extensions.
NOTES¶
In glibc 2.2, these functions use the DES algorithm.
EXAMPLE¶
#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <crypt.h>
int
main(void)
{
char key[64];
char orig[9] = "eggplant";
char buf[64];
char txt[9];
int i, j;
for (i = 0; i < 64; i++) {
key[i] = rand() & 1;
}
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
buf[i * 8 + j] = orig[i] >> j & 1;
}
setkey(key);
}
printf("Before encrypting: %s\n", orig);
encrypt(buf, 0);
for (i = 0; i < 8; i++) {
for (j = 0, txt[i] = '\0'; j < 8; j++) {
txt[i] |= buf[i * 8 + j] << j;
}
txt[8] = '\0';
}
printf("After encrypting: %s\n", txt);
encrypt(buf, 1);
for (i = 0; i < 8; i++) {
for (j = 0, txt[i] = '\0'; j < 8; j++) {
txt[i] |= buf[i * 8 + j] << j;
}
txt[8] = '\0';
}
printf("After decrypting: %s\n", txt);
exit(EXIT_SUCCESS);
}
SEE ALSO¶
cbc_crypt(3),
crypt(3),
ecb_crypt(3),
COLOPHON¶
This page is part of release 4.10 of the Linux
man-pages project. A
description of the project, information about reporting bugs, and the latest
version of this page, can be found at
https://www.kernel.org/doc/man-pages/.