NAME¶
DES_random_key, DES_set_key, DES_key_sched, DES_set_key_checked,
DES_set_key_unchecked, DES_set_odd_parity, DES_is_weak_key, 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_cbc_cksum, DES_quad_cksum,
DES_string_to_key, DES_string_to_2keys, DES_fcrypt, DES_crypt, 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, unsigned char *output,
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);
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);
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 algorithm.
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 is 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.
DES_random_key() generates a random key. The PRNG must be seeded prior to
using this function (see
rand(3)). If the PRNG could not generate a
secure key, 0 is returned.
Before a DES key can be used, it must be converted into the architecture
dependent
DES_key_schedule via the
DES_set_key_checked() or
DES_set_key_unchecked() function.
DES_set_key_checked() will check that the key passed is of odd parity and
is not a week 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.
DES_set_key() works like
DES_set_key_checked() if the
DES_check_key flag is non-zero, otherwise like
DES_set_key_unchecked(). These functions are available for
compatibility; it is recommended to use a function that does not depend on a
global variable.
DES_set_odd_parity() sets the parity of the passed
key to odd.
DES_is_weak_key() returns 1 if the passed key is a weak key, 0 if it is
ok.
The following routines mostly operate on an input and output stream of
DES_cblocks.
DES_ecb_encrypt() is the basic DES encryption routine that encrypts or
decrypts a single 8-byte
DES_cblock in
electronic 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 ciphertext) is decrypted into the
output (now cleartext). Input
and output may overlap.
DES_ecb_encrypt() does not return a value.
DES_ecb3_encrypt() encrypts/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 of if
ks1,
ks2 and
ks3 are the same, it is equivalent to just encryption using ECB mode
and
ks1 as the key.
The macro
DES_ecb2_encrypt() is provided to perform two-key Triple-DES
encryption by using
ks1 for the final encryption.
DES_ncbc_encrypt() encrypts/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.
DES_xcbc_encrypt() is RSA's DESX mode of DES. It uses
inw and
outw to 'whiten' the encryption.
inw and
outw are secret
(unlike the iv) and are as such, part of the key. So the key is sort of 24
bytes. This is much better than CBC DES.
DES_ede3_cbc_encrypt() implements outer triple CBC DES encryption with
three keys. This means that each DES operation inside the CBC mode is 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.
DES_pcbc_encrypt() encrypt/decrypts using the propagating cipher block
chaining mode used by Kerberos v4. Its parameters are the same as
DES_ncbc_encrypt().
DES_cfb_encrypt() encrypt/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. Note: 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.
DES_cfb64_encrypt() implements CFB mode of DES with 64bit feedback. Why
is this useful you ask? Because this routine will allow you to encrypt an
arbitrary number of bytes, no 8 byte padding. Each call to this routine will
encrypt the input bytes to output and then update ivec and num. num contains
'how far' we are though ivec. If this does not make much sense, read more
about cfb mode of DES :-).
DES_ede3_cfb64_encrypt() and
DES_ede2_cfb64_encrypt() is the same
as
DES_cfb64_encrypt() except that Triple-DES is used.
DES_ofb_encrypt() encrypts using output 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. Note: 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.
DES_ofb64_encrypt() is the same as
DES_cfb64_encrypt() using
Output Feed Back mode.
DES_ede3_ofb64_encrypt() and
DES_ede2_ofb64_encrypt() is the same
as
DES_ofb64_encrypt(), using Triple-DES.
The following functions are included in the DES library for compatibility with
the MIT Kerberos library.
DES_cbc_cksum() 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
Kerberos v4. Other applications should use
EVP_DigestInit(3) etc.
instead.
DES_quad_cksum() 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
output.
The following are DES-based transformations:
DES_fcrypt() is a fast version of the Unix
crypt(3) function. This
version takes only a small amount of space relative to other fast
crypt() implementations. This is different to 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.
DES_crypt() is a faster replacement 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(3).
DES_enc_write() 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.
DES_enc_read() 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 vector.
Warning: 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. So don't use these functions
unless you are sure you know what you do (in which case you might not want to
use them anyway). They cannot handle non-blocking sockets.
DES_enc_read() uses an internal state and thus cannot be used on
multiple files.
DES_rw_mode is used to specify the encryption mode to use with
DES_enc_read() and
DES_end_write(). If set to
DES_PCBC_MODE (the default), DES_pcbc_encrypt is used. If 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.
BUGS¶
DES_3cbc_encrypt() is flawed and must not be used in applications.
DES_cbc_encrypt() does not modify
ivec; use
DES_ncbc_encrypt() instead.
DES_cfb_encrypt() and
DES_ofb_encrypt() operates 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 1st 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 4th input byte. The same holds
for output. This function has been implemented this way because most people
will be using a multiple of 8 and because once you get into pulling bytes
input bytes apart things get ugly!
DES_string_to_key() is available for backward compatibility with the MIT
library. New applications should use a cryptographic hash function. The same
applies for
DES_string_to_2key().
ANSI X3.106
The
des library was written to be source code compatible with the MIT
Kerberos library.
SEE ALSO¶
crypt(3),
des_modes(7),
evp(3),
rand(3)
HISTORY¶
In OpenSSL 0.9.7, all des_ functions were renamed to DES_ to avoid clashes with
older versions of libdes. Compatibility des_ functions are provided for a
short while, as well as
crypt(). Declarations for these are in
<openssl/des_old.h>. There is no DES_ variant for
des_random_seed(). This will happen to other functions as well if they
are deemed redundant (
des_random_seed() just calls
RAND_seed()
and is present for backward compatibility only), buggy or already scheduled
for removal.
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() and
des_string_to_key() are available in the MIT Kerberos library;
des_check_key_parity(),
des_fixup_key_parity() and
des_is_weak_key() are available in newer versions of that library.
des_set_key_checked() and
des_set_key_unchecked() were added in
OpenSSL 0.9.5.
des_generate_random_block(),
des_init_random_number_generator(),
des_new_random_key(),
des_set_random_generator_seed() and
des_set_sequence_number() and
des_rand_data() are used in newer
versions of Kerberos but are not implemented here.
des_random_key() generated cryptographically weak random data in SSLeay
and in OpenSSL prior version 0.9.5, as well as in the original MIT library.
AUTHOR¶
Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project
(
http://www.openssl.org).