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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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ENCRYPT(3) Linux Programmer's Manual ENCRYPT(3)
encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
#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.
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 current_saltbits;
int direction;
int 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.)
Because they employ the DES block cipher, which is no longer
considered secure, crypt(), crypt_r(), setkey(), and setkey_r()
were removed in glibc 2.28. Applications should switch to a
modern cryptography library, such as libgcrypt.
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.
Availability in glibc
See crypt(3).
Features in glibc
In glibc 2.2, these functions use the DES algorithm.
#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];
for (int i = 0; i < 64; i++) {
key[i] = rand() & 1;
}
for (int i = 0; i < 8; i++) {
for (int 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 (int i = 0; i < 8; i++) {
for (int 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 (int i = 0; i < 8; i++) {
for (int 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);
}
cbc_crypt(3), crypt(3), ecb_crypt(3),
This page is part of release 5.10 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/.
2020-11-01 ENCRYPT(3)
Pages that refer to this page: crypt(3)
Copyright and license for this manual page
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