NAME
encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
SYNOPSIS
#define _XOPEN_SOURCE
#include <unistd.h>
I void encrypt(char block [64], int edflag );
#define _XOPEN_SOURCE
#include <stdlib.h>
I void setkey(const char * key );
#define _GNU_SOURCE
I #include <crypt.h>
I void setkey_r(const char * key , struct crypt_data * data );
I 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
R setkey ()
function sets the key used by
R 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
R 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
R setkey_r ()
and
R 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
R 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.
R ENOSYS
The function is not provided.
(For example because of former USA export restrictions.)
CONFORMING TO
The functions
R encrypt ()
and
R setkey ()
conform to SVr4, SUSv2, and POSIX.1-2001.
The functions
R encrypt_r ()
and
R setkey_r ()
are GNU extensions.
NOTES
In glibc 2.2 these functions use the DES algorithm.
EXAMPLE
You need to link with libcrypt to compile this example with glibc 2.2.
To do useful work the key[] and txt[] arrays must be filled with a
useful bit pattern.
#define _XOPEN_SOURCE
#include <unistd.h>
#include <stdlib.h>
int
main(void)
{
char key[64]; /* bit pattern for key */
char txt[64]; /* bit pattern for messages */
setkey(key);
encrypt(txt, 0); /* encode */
encrypt(txt, 1); /* decode */
}
SEE ALSO
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