des(3)des(3)NAME
des, des_random_key, des_set_key, des_set_key_checked,
des_set_key_unchecked, des_set_odd_parity, des_ecb_encrypt,
des_ecb2_encrypt, des_ecb3_encrypt, des_ncbc_encrypt, des_cfb_encrypt,
des_ofb_encrypt, des_pcbc_encrypt, des_cfb64_encrypt,
des_ofb64_encrypt, des_xcbc_encrypt, des_ede2_cbc_encrypt,
des_ede2_cfb64_encrypt, des_ede2_ofb64_encrypt, des_ede3_cbc_encrypt,
des_ede3_cbcm_encrypt, des_ede3_cfb64_encrypt, des_ede3_ofb64_encrypt,
des_read_password, des_read_2passwords, des_read_pw_string,
des_cbc_cksum, des_string_to_2keys, des_fcrypt, des_enc_read,
des_enc_write - DES encryption
SYNOPSIS
#include <openssl/des.h>
void des_random_key(
des_cblock *ret ); int des_set_key(
const_des_cblock *key,
des_key_schedule schedule ); int des_key_sched(
const_des_cblock *key,
des_key_schedule schedule ); int des_set_key_checked(
const_des_cblock *key,
des_key_schedule schedule ); void des_set_key_unchecked(
const_des_cblock *key,
des_key_schedule schedule ); void des_set_odd_parity(
des_cblock *key ); int des_is_weak_key(
const_des_cblock *key ); void des_ecb_encrypt(
const_des_cblock *input,
des_cblock *output,
des_key_schedule ks,
int enc ); void des_ecb2_encrypt(
const_des_cblock *input,
des_cblock *output,
des_key_schedule ks1,
des_key_schedule ks2,
int enc ); void des_ecb3_encrypt(
const_des_cblock *input,
, des_cblock *output,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
int enc ); void des_ncbc_encrypt(
const unsigned char *input,
unsigned char *output,
long length,
des_key_schedule schedule,
des_cblock *ivec,
int enc ); void des_cfb_encrypt(
const unsigned char *in,
unsigned char *out,
int numbits,
long length,
des_key_schedule schedule,
des_cblock *ivec,
int enc ); void des_ofb_encrypt(
const unsigned char *in,
unsigned char *out,
int numbits,
long length,
des_key_schedule schedule,
des_cblock *ivec ); void des_pcbc_encrypt(
const unsigned char *input,
nsigned char *output,
u,
long length,
des_key_schedule schedule,
des_cblock *ivec,
int enc ); void des_cfb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule schedule,
des_cblock *ivec,
int *num,
int enc ); void des_ofb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule schedule,
des_cblock *ivec,
int *num ); void des_xcbc_encrypt(
const unsigned char *input,
unsigned char *output,
long length,
des_key_schedule schedule,
des_cblock *ivec,
const_des_cblock *inw,
const_des_cblock *outw,
int enc ); void des_ede2_cbc_encrypt(
const unsigned char *input,
unsigned char *output,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_cblock *ivec,
int enc ); void des_ede2_cfb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_cblock *ivec,
int *num,
int enc ); void des_ede2_ofb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_cblock *ivec,
int *num ); void des_ede3_cbc_encrypt(
const unsigned char *input,
unsigned char *output,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
des_cblock *ivec,
int enc ); void des_ede3_cbcm_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
des_cblock *ivec1,
des_cblock *ivec2,
int enc ); void des_ede3_cfb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
des_cblock *ivec,
int *num,
int enc ); void des_ede3_ofb64_encrypt(
const unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
des_cblock *ivec,
int *num ); int des_read_password(
des_cblock *key,
const char *prompt,
int verify ); int des_read_2passwords(
des_cblock *key1,
des_cblock *key2,
const char *prompt,
int verify ); int des_read_pw_string(
char *buf,
int length,
const char *prompt,
int verify ); DES_LONG des_cbc_cksum(
const unsigned char *input,
des_cblock *output,
long length,
des_key_schedule schedule,
const_des_cblock *ivec ); DES_LONG des_quad_cksum(
const unsigned char *input,
des_cblock output[],
long length,
int out_count,
des_cblock *seed ); void des_string_to_key(
const char *str,
des_cblock *key ); void des_string_to_2keys(
const char *str,
des_cblock *key1,
des_cblock *key2 ); char *des_fcrypt(
const char *buf,
const char *salt,
char *ret ); char *des_crypt(
const char *buf,
const char *salt ); char *crypt(
const char *buf,
const char *salt ); int des_enc_read(
int fd,
void *buf,
int len,
des_key_schedule sched,
des_cblock *iv ); int des_enc_write(
int fd,
const void *buf,
int len,
des_key_schedule sched,
des_cblock *iv );
DESCRIPTION
This library contains a fast implementation of the DES encryption algo‐
rithm.
There are two phases to the use of DES encryption. The first is the
generation of a des_key_schedule from a key; the second is the actual
encryption. A DES key is of type des_cblock. This type consists of 8
bytes with odd parity. The least significant bit in each byte is the
parity bit. The key schedule is an expanded form of the key; it is
used to speed the encryption process.
The des_random_key() generates a random key. The PRNG must be seeded
prior to using this function (see rand_ssl(3); for backward compatibil‐
ity the des_random_seed() function is available as well). If the PRNG
could not generate a secure key, 0 is returned. In earlier versions of
the library, des_random_key() did not generate secure keys.
Before a DES key can be used, it must be converted into the architec‐
ture dependent des_key_schedule via the des_set_key_checked() or
des_set_key_unchecked() functions.
The des_set_key_checked() function will check that the key passed is of
odd parity and is not a weak or semi-weak key. If the parity is wrong,
then -1 is returned. If the key is a weak key, then -2 is returned.
If an error is returned, the key schedule is not generated.
The des_set_key() function (called des_key_sched() in the MIT library)
works like des_set_key_checked() if the des_check_key flag is non-zero;
otherwise, it works like des_set_key_unchecked(). These functions are
available for compatibility; we recommend you use a function that does
not depend on a global variable.
The des_set_odd_parity() function (called des_fixup_key_parity() in the
MIT library) sets the parity of the passed key to odd.
The des_is_weak_key() function returns 1 is the passed key is a weak
key, 0 if it is ok. The probability that a randomly generated key is
weak is 1/2^52.
The following routines mostly operate on an input and output stream of
des_cblock: The des_ecb_encrypt() function is the basic DES encryption
routine that encrypts or decrypts a single 8-byte des_cblock in elec‐
tronic code book (ECB) mode. It always transforms the input data,
pointed to by input, into the output data, pointed to by the output
argument. If the encrypt argument is non-zero (DES_ENCRYPT), the input
(cleartext) is encrypted in to the output (ciphertext) using the
key_schedule specified by the schedule argument, previously set via
des_set_key. If encrypt is zero (DES_DECRYPT), the input (now cipher‐
text) is decrypted into the output (now cleartext). Input and output
may overlap. The des_ecb_encrypt() function does not return a value.
The des_ecb3_encrypt() function encrypts and decrypts the input block
by using three-key Triple-DES encryption in ECB mode. This involves
encrypting the input with ks1, decrypting with the key schedule ks2,
and then encrypting with ks3. This routine greatly reduces the chances
of brute force breaking of DES and has the advantage if ks1, ks2 and
ks3 are the same. It is equivalent to encryption using ECB mode and ks1
as the key. The des_ecb2_encrypt() macro is provided to perform two-
key Triple-DES encryption by using ks1 for the final encryption. The
des_ncbc_encrypt() function encrypts and decrypts using the cipher-
block-chaining (CBC) mode of DES. If the encrypt argument is non-zero,
the routine cipher-block-chain encrypts the cleartext data pointed to
by the input argument into the ciphertext pointed to by the output
argument, using the key schedule provided by the schedule argument, and
initialization vector provided by the ivec argument. If the length
argument is not an integral multiple of eight bytes, the last block is
copied to a temporary area and zero filled. The output is always an
integral multiple of eight bytes. The des_xcbc_encrypt() function is
RSA's DESX mode of DES. It uses inw and outw to whiten the encryption.
The inw and outw are secret (unlike the iv) and are part of the key.
So the key is sort of 24 bytes. This is much better than CBC DES. The
des_ede3_cbc_encrypt() function implements outer triple CBC DES encryp‐
tion with three keys. This means that each DES operation inside the CBC
mode is really an C=E(ks3,D(ks2,E(ks1,M))). This mode is used by SSL.
The des_ede2_cbc_encrypt() macro implements two-key Triple-DES by
reusing ks1 for the final encryption. C=E(ks1,D(ks2,E(ks1,M))). This
form of Triple-DES is used by the RSAREF library. The
des_pcbc_encrypt() function encrypts and decrypts using the propagating
cipher block chaining mode used by Kerberos v4. Its parameters are the
same as des_ncbc_encrypt(). The des_cfb_encrypt() function encrypts
and decrypts using cipher feedback mode. This method takes an array of
characters as input and outputs and array of characters. It does not
require any padding to 8 character groups. The ivec variable is changed
and the new changed value needs to be passed to the next call to this
function. Since this function runs a complete DES ECB encryption per
numbits, this function is only suggested for use when sending small
numbers of characters. The des_cfb64_encrypt() function implements CFB
mode of DES with 64-bit feedback. This is useful because this routine
will allow you to encrypt an arbitrary number of bytes, no 8-byte pad‐
ding. Each call to this routine will encrypt the input bytes to output
and then update ivec and num. The num shows where you are through
ivec. The des_ede3_cfb64_encrypt() and des_ede2_cfb64_encrypt() func‐
tions are the same as the des_cfb64_encrypt() function except that
Triple-DES is used. The des_ofb_encrypt() function encrypts using out‐
put feedback mode. This method takes an array of characters as input
and outputs and array of characters. It does not require any padding
to 8-character groups. The ivec variable is changed and the new changed
value needs to be passed to the next call to this function. Since this
function runs a complete DES ECB encryption per numbits, we recommend
using this function only when sending small numbers of characters. The
des_ofb64_encrypt() function is the same as the des_cfb64_encrypt()
function using Output Feed Back mode. The des_ede3_ofb64_encrypt() and
des_ede2_ofb64_encrypt() functions are the same as des_ofb64_encrypt()
using Triple-DES.
The following functions are included in the DES library for compatibil‐
ity with the MIT Kerberos library. The des_read_pw_string() function is
also available under the name EVP_read_pw_string(). The
des_read_pw_string() function writes the string specified by prompt to
standard output, turns echo off and reads in input string from the ter‐
minal. The string is returned in buf, which must have space for at
least length bytes. If verify is set, the user is asked for the pass‐
word twice. Unless the two copies match, an error is returned. A
return code of -1 indicates a system error, 1 failure due to use inter‐
action, and 0 is success. The des_read_password() function does the
same and converts the password to a DES key by calling
des_string_to_key(); the des_read_2password() function operates in the
same way as des_read_password() except that it generates two keys by
using the des_string_to_2key() function. The des_string_to_key() func‐
tion is available for backward compatibility with the MIT library. New
applications should use a cryptographic hash function. The same
applies for the des_string_to_2key() function. The des_cbc_cksum()
function produces an 8-byte checksum based on the input stream (via CBC
encryption). The last 4 bytes of the checksum are returned and the
complete 8 bytes are placed in output. This function is used by Ker‐
beros v4. Other applications should use EVP_DigestInit() etc. instead.
The des_quad_cksum() function is a Kerberos v4 function. It returns a
4-byte checksum from the input bytes. The algorithm can be iterated
over the input, depending on out_count, 1, 2, 3 or 4 times. If output
is non-NULL, the 8 bytes generated by each pass are written into out‐
put.
The following are DES-based transformations: The des_fcrypt() function
is a fast version of the Unix crypt() function. This version takes
only a small amount of space relative to other fast crypt() implementa‐
tions. This is different from the normal crypt in that the third
parameter is the buffer that the return value is written into. It
needs to be at least 14 bytes long. This function is thread safe,
unlike the normal crypt. The des_crypt() function is a faster replace‐
ment for the normal system crypt(). This function calls des_fcrypt()
with a static array passed as the third parameter. This emulates the
normal non-thread safe semantics of crypt(). The des_enc_write() func‐
tion writes len bytes to file descriptor fd from buffer buf. The data
is encrypted via pcbc_encrypt (default) using sched for the key and iv
as a starting vector. The actual data send down fd consists of 4 bytes
(in network byte order) containing the length of the following
encrypted data. The encrypted data then follows, padded with random
data out to a multiple of 8 bytes. The des_enc_read() function is used
to read len bytes from file descriptor fd into buffer buf. The data
being read from fd is assumed to have come from des_enc_write() and is
decrypted using sched for the key schedule and iv for the initial vec‐
tor.
Note
The data format used by des_enc_write() and des_enc_read() has a
cryptographic weakness: When asked to write more than MAXWRITE
bytes, des_enc_write() will split the data into several chunks
that are all encrypted using the same IV. We do not recommend
using these functions unless you are sure you know what you do.
They cannot handle non-blocking sockets. The des_enc_read()
function uses an internal state and cannot be used on multiple
files. The des_rw_mode specifies the encryption mode to use
with the des_enc_read() and des_end_write() functions. If it is
set to DES_PCBC_MODE (the default), des_pcbc_encrypt is used.
If it is set to DES_CBC_MODE, des_cbc_encrypt is used.
NOTES
Single-key DES is insecure due to its short key size. ECB mode is not
suitable for most applications; see des_modes(7).
The evp(3) library provides higher-level encryption functions.
RESTRICTIONS
The des_3cbc_encrypt() function is flawed and must not be used in
applications.
The des_cbc_encrypt() function does not modify ivec; use the
des_ncbc_encrypt() function instead.
The des_cfb_encrypt() and des_ofb_encrypt() functions operate on input
of 8 bits. What this means is that if you set numbits to 12, and length
to 2, the first 12 bits will come from the first input byte and the low
half of the second input byte. The second 12 bits will have the low 8
bits taken from the 3rd input byte and the top 4 bits taken from the
fourth input byte. The same holds for output. This function has been
implemented this way because most people will be using a multiple of 8.
The des_read_pw_string() function is the most machine/OS dependent
function and normally generates the most problems when porting this
code.
The des library was written to be source code compatible with the MIT
Kerberos library. It conforms to ANSI X3.106.
HISTORY
The des_cbc_cksum(), des_cbc_encrypt(), des_ecb_encrypt(),
des_is_weak_key(), des_key_sched(), des_pcbc_encrypt(),
des_quad_cksum(), des_random_key(), des_read_password(), and
des_string_to_key() functions are available in the MIT Kerberos
library; the des_check_key_parity(), des_fixup_key_parity(), and
des_is_weak_key() functions are available in newer versions of that
library.
The des_set_key_checked() and des_set_key_unchecked() functions were
added in OpenSSL 0.9.5.
The des_generate_random_block(), des_init_random_number_generator(),
des_new_random_key(), des_set_random_generator_seed(),
des_set_sequence_number(), and des_rand_data() functions are used in
newer versions of Kerberos but are not implemented here.
The des_random_key() function generated cryptographically weak random
data in SSLeay and in OpenSSL prior version 0.9.5, as well as in the
original MIT library.
Author is Eric Young (eay@cryptsoft.com). Modified for the OpenSSL
project (http://www.openssl.org).
SEE ALSO
Functions: crypt(3), des_crypt(3), evp(3), rand_ssl(3)
Files: des_modes(7)des(3)
