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des(3)				    OpenSSL				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_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 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 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.

       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().

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
       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).

1.0.1e				  2013-02-11				des(3)

NAME | SYNOPSIS | DESCRIPTION | NOTES | BUGS | CONFORMING TO | SEE ALSO | HISTORY | AUTHOR

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