des(3)
des(3) 0.9.6h (2000-10-11) des(3)
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_read_password,
des_read_2passwords, des_read_pw_string, 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);
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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);
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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 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); for
backward compatibility the function des_random_seed() 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
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.
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des_set_key() (called des_key_sched() in the MIT library)
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() (called des_fixup_key_parity() in the
MIT library) sets the parity of the passed key to odd.
des_is_weak_key() 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, so it is not really worth checking
for them.
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
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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 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.
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.
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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_read_pw_string() is also available under the name
EVP_read_pw_string().
des_read_pw_string() writes the string specified by prompt
to standard output, turns echo off and reads in input string
from the terminal. 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 password twice and unless the
two copies match, an error is returned. A return code of -1
indicates a system error, 1 failure due to use interaction,
and 0 is success.
des_read_password() does the same and converts the password
to a DES key by calling des_string_to_key();
des_read_2password() operates in the same way as
des_read_password() except that it generates two keys by
using the des_string_to_2key() function.
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().
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.
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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
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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_read_pw_string() is the most machine/OS dependent
function and normally generates the most problems when
porting this code.
CONFORMING TO
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
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() 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).
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