Originální popis anglicky:
encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
Návod, kniha: Cryptographic Functions
#define _XOPEN_SOURCE
#include <unistd.h>
void encrypt(char block[64], int edflag);
#define _XOPEN_SOURCE
#include <stdlib.h>
void setkey(const char *key);
#define _GNU_SOURCE
#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.
These functions encrypt and decrypt 64-bit messages. The
setkey()
function sets the key used by
encrypt(). The
key parameter 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 parameter 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, initialized;
};
Before calling
setkey_r() set
data->initialized to zero.
These functions do not return any value.
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.)
You need to link with libcrypt to compile this example with glibc2.2. To do
useful work the key[] and txt[] array must be filled with a useful bit
pattern. Note that the <crypt.h> header unconditionally gives the
prototypes for setkey() and encrypt().
#include <crypt.h>
main() {
char key[64]; /* bit pattern for key */
char txt[64]; /* bit pattern for messages */
setkey(key);
encrypt(txt, 0); /* encode */
encrypt(txt, 1); /* decode */
}
In glibc2.2 these functions use the DES algorithm.
The functions
encrypt() and
setkey() conform to SVID, SUSv2, and
POSIX 1003.1-2001. The functions
encrypt_r() and
setkey_r() are
GNU extensions.
cbc_crypt(3),
crypt(3),
ecb_crypt(3),
fcrypt(3)
