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.TH DES 1 

.SH NAME

=pod

=head1 NAME

des - encrypt or decrypt data using Data Encryption Standard

.SH SYNOPSIS

.B des

=head1 SYNOPSIS

B<des>

(

.B \-e

B<-e>

|

.B \-E

B<-E>

) | (

.B \-d

B<-d>

|

.B \-D

B<-D>

) | (

.B \-\fR[\fPcC\fR][\fPckname\fR]\fP

B<->[B<cC>][B<ckname>]

) |

[

.B \-b3hfs

B<-b3hfs>

] [

.B \-k

.I key

B<-k>

I<key>

]

] [

.B \-u\fR[\fIuuname\fR]

B<-u>[I<uuname>]

[

.I input-file

I<input-file>

[

.I output-file

I<output-file>

] ]

.SH DESCRIPTION

.B des

=head1 NOTE

This page describes the B<des> stand-alone program, not the B<openssl des>

command.

=head1 DESCRIPTION

B<des>

encrypts and decrypts data using the

Data Encryption Standard algorithm.

One of

.B \-e, \-E

B<-e>, B<-E>

(for encrypt) or

.B \-d, \-D

B<-d>, B<-D>

(for decrypt) must be specified.

It is also possible to use

.B \-c

B<-c>

or

.B \-C

B<-C>

in conjunction or instead of the a encrypt/decrypt option to generate

a 16 character hexadecimal checksum, generated via the

.I des_cbc_cksum.

.LP

I<des_cbc_cksum>.

Two standard encryption modes are supported by the

.B des

B<des>

program, Cipher Block Chaining (the default) and Electronic Code Book

(specified with

.B \-b

).

.LP

B<-b>).

The key used for the DES

algorithm is obtained by prompting the user unless the

.B `\-k

.I key'

B<-k>

I<key>

option is given.

If the key is an argument to the

.B des

B<des>

command, it is potentially visible to users executing

.BR ps (1)

ps(1)

or a derivative.  To minimise this possibility,

.B des

B<des>

takes care to destroy the key argument immediately upon entry.

If your shell keeps a history file be careful to make sure it is not

world readable.

.LP

Since this program attempts to maintain compatability with sunOS's

Since this program attempts to maintain compatibility with sunOS's

des(1) command, there are 2 different methods used to convert the user

supplied key to a des key.

Whenever and one or more of

.B \-E, \-D, \-C

B<-E>, B<-D>, B<-C>

or

.B \-3

B<-3>

options are used, the key conversion procedure will not be compatible

with the sunOS des(1) version but will use all the user supplied

character to generate the des key.

.B des

B<des>

command reads from standard input unless

.I input-file

I<input-file>

is specified and writes to standard output unless

.I output-file

I<output-file>

is given.

.SH OPTIONS

.TP

.B \-b

=head1 OPTIONS

=over 4

=item B<-b>

Select ECB

(eight bytes at a time) encryption mode.

.TP

.B \-3

=item B<-3>

Encrypt using triple encryption.

By default triple cbc encryption is used but if the

.B \-b

option is used then triple ecb encryption is performed.

B<-b>

option is used then triple ECB encryption is performed.

If the key is less than 8 characters long, the flag has no effect.

.TP

.B \-e

=item B<-e>

Encrypt data using an 8 byte key in a manner compatible with sunOS

des(1).

.TP

.B \-E

=item B<-E>

Encrypt data using a key of nearly unlimited length (1024 bytes).

This will product a more secure encryption.

.TP

.B \-d

Decrypt data that was encrypted with the \-e option.

.TP

.B \-D

Decrypt data that was encrypted with the \-E option.

.TP

.B \-c

=item B<-d>

Decrypt data that was encrypted with the B<-e> option.

=item B<-D>

Decrypt data that was encrypted with the B<-E> option.

=item B<-c>

Generate a 16 character hexadecimal cbc checksum and output this to

stderr.

If a filename was specified after the

.B \-c

B<-c>

option, the checksum is output to that file.

The checksum is generated using a key generated in a sunOS compatible

manner.

.TP

.B \-C

=item B<-C>

A cbc checksum is generated in the same manner as described for the

.B \-c

B<-c>

option but the DES key is generated in the same manner as used for the

.B \-E

B<-E>

and

.B \-D

B<-D>

options

.TP

.B \-f

=item B<-f>

Does nothing - allowed for compatibility with sunOS des(1) command.

.TP

.B \-s

=item B<-s>

Does nothing - allowed for compatibility with sunOS des(1) command.

.TP

.B "\-k \fIkey\fP"

=item B<-k> I<key>

Use the encryption 

.I key

I<key>

specified.

.TP

.B "\-h"

=item B<-h>

The

.I key

I<key>

is assumed to be a 16 character hexadecimal number.

If the

.B "\-3"

B<-3>

option is used the key is assumed to be a 32 character hexadecimal

number.

.TP

.B \-u

=item B<-u>

This flag is used to read and write uuencoded files.  If decrypting,

the input file is assumed to contain uuencoded, DES encrypted data.

If encrypting, the characters following the -u are used as the name of

If encrypting, the characters following the B<-u> are used as the name of

the uuencoded file to embed in the begin line of the uuencoded

output.  If there is no name specified after the -u, the name text.des

output.  If there is no name specified after the B<-u>, the name text.des

will be embedded in the header.

.SH SEE ALSO

.B ps (1)

.B des_crypt(3)

.SH BUGS

.LP

=head1 SEE ALSO

ps(1),

L<des_crypt(3)|des_crypt(3)>

=head1 BUGS

The problem with using the

.B -e

B<-e>

option is the short key length.

It would be better to use a real 56-bit key rather than an

ASCII-based 56-bit pattern.  Knowing that the key was derived from ASCII

radically reduces the time necessary for a brute-force cryptographic attack.

My attempt to remove this problem is to add an alternative text-key to

DES-key function.  This alternative function (accessed via

.B -E, -D, -S

B<-E>, B<-D>, B<-S>

and

.B -3

)

B<-3>)

uses DES to help generate the key.

.LP

Be carefully when using the -u option.  Doing des -ud <filename> will

not decrypt filename (the -u option will gobble the d option).

.LP

Be carefully when using the B<-u> option.  Doing B<des -ud> I<filename> will

not decrypt filename (the B<-u> option will gobble the B<-d> option).

The VMS operating system operates in a world where files are always a

multiple of 512 bytes.  This causes problems when encrypted data is

send from unix to VMS since a 88 byte file will suddenly be padded

with 424 null bytes.  To get around this problem, use the -u option

send from Unix to VMS since a 88 byte file will suddenly be padded

with 424 null bytes.  To get around this problem, use the B<-u> option

to uuencode the data before it is send to the VMS system.

.SH AUTHOR

.LP

=head1 AUTHOR

Eric Young (eay@cryptsoft.com)

=cut

.TH DES_CRYPT 3 

.SH NAME

des_read_password, des_read_2password,

des_string_to_key, des_string_to_2key, des_read_pw_string,

des_random_key, des_set_key,

des_key_sched, des_ecb_encrypt, des_ecb3_encrypt, des_cbc_encrypt,

des_3cbc_encrypt,

des_pcbc_encrypt, des_cfb_encrypt, des_ofb_encrypt,

des_cbc_cksum, des_quad_cksum,

des_enc_read, des_enc_write, des_set_odd_parity,

des_is_weak_key, crypt \- (non USA) DES encryption

.SH SYNOPSIS

.nf

.nj

.ft B

#include <des.h>

.PP

.B int des_read_password(key,prompt,verify)

des_cblock *key;

char *prompt;

int verify;

.PP

.B int des_read_2password(key1,key2,prompt,verify)

des_cblock *key1,*key2;

char *prompt;

int verify;

.PP

.B int des_string_to_key(str,key)

char *str;

des_cblock *key;

.PP

.B int des_string_to_2keys(str,key1,key2)

char *str;

des_cblock *key1,*key2;

.PP

.B int des_read_pw_string(buf,length,prompt,verify)

char *buf;

int length;

char *prompt;

int verify;

.PP

.B int des_random_key(key)

des_cblock *key;

.PP

.B int des_set_key(key,schedule)

des_cblock *key;

des_key_schedule schedule;

.PP

.B int des_key_sched(key,schedule)

des_cblock *key;

des_key_schedule schedule;

.PP

.B int des_ecb_encrypt(input,output,schedule,encrypt)

des_cblock *input;

des_cblock *output;

des_key_schedule schedule;

int encrypt;

.PP

.B int des_ecb3_encrypt(input,output,ks1,ks2,encrypt)

des_cblock *input;

des_cblock *output;

des_key_schedule ks1,ks2;

int encrypt;

.PP

.B int des_cbc_encrypt(input,output,length,schedule,ivec,encrypt)

des_cblock *input;

des_cblock *output;

long length;

des_key_schedule schedule;

des_cblock *ivec;

int encrypt;

.PP

.B int des_3cbc_encrypt(input,output,length,sk1,sk2,ivec1,ivec2,encrypt)

des_cblock *input;

des_cblock *output;

long length;

des_key_schedule sk1;

des_key_schedule sk2;

des_cblock *ivec1;

des_cblock *ivec2;

int encrypt;

.PP

.B int des_pcbc_encrypt(input,output,length,schedule,ivec,encrypt)

des_cblock *input;

des_cblock *output;

long length;

des_key_schedule schedule;

des_cblock *ivec;

int encrypt;

.PP

.B int des_cfb_encrypt(input,output,numbits,length,schedule,ivec,encrypt)

unsigned char *input;

unsigned char *output;

int numbits;

long length;

des_key_schedule schedule;

des_cblock *ivec;

int encrypt;

.PP

.B int des_ofb_encrypt(input,output,numbits,length,schedule,ivec)

unsigned char *input,*output;

int numbits;

long length;

des_key_schedule schedule;

des_cblock *ivec;

.PP

.B unsigned long des_cbc_cksum(input,output,length,schedule,ivec)

des_cblock *input;

des_cblock *output;

long length;

des_key_schedule schedule;

des_cblock *ivec;

.PP

.B unsigned long des_quad_cksum(input,output,length,out_count,seed)

des_cblock *input;

des_cblock *output;

long length;

int out_count;

des_cblock *seed;

.PP

.B int des_check_key;

.PP

.B int des_enc_read(fd,buf,len,sched,iv)

int fd;

char *buf;

int len;

des_key_schedule sched;

des_cblock *iv;

.PP

.B int des_enc_write(fd,buf,len,sched,iv)

int fd;

char *buf;

int len;

des_key_schedule sched;

des_cblock *iv;

.PP

.B extern int des_rw_mode;

.PP

.B void des_set_odd_parity(key)

des_cblock *key;

.PP

.B int des_is_weak_key(key)

des_cblock *key;

.PP

.B char *crypt(passwd,salt)

char *passwd;

char *salt;

.PP

.fi

.SH DESCRIPTION

This library contains a fast implementation of the DES encryption

algorithm.

.PP

There are two phases to the use of DES encryption.

The first is the generation of a

.I des_key_schedule

from a key,

the second is the actual encryption.

A des key is of type

.I des_cblock.

This type is made from 8 characters with odd parity.

The least significant bit in the character is the parity bit.

The key schedule is an expanded form of the key; it is used to speed the

encryption process.

.PP

.I des_read_password

writes the string specified by prompt to the standard output,

turns off echo and reads an input string from standard input

until terminated with a newline.

If verify is non-zero, it prompts and reads the input again and verifies

that both entered passwords are the same.

The entered string is converted into a des key by using the

.I des_string_to_key

routine.

The new key is placed in the

.I des_cblock

that was passed (by reference) to the routine.

If there were no errors,

.I des_read_password

returns 0,

-1 is returned if there was a terminal error and 1 is returned for

any other error.

.PP

.I des_read_2password

operates in the same way as

.I des_read_password

except that it generates 2 keys by using the

.I des_string_to_2key

function.

.PP

.I des_read_pw_string

is called by

.I des_read_password

to read and verify a string from a terminal device.

The string is returned in

.I buf.

The size of

.I buf

is passed to the routine via the

.I length

parameter.

.PP

.I des_string_to_key

converts a string into a valid des key.

.PP

.I des_string_to_2key

converts a string into 2 valid des keys.

This routine is best suited for used to generate keys for use with

.I des_ecb3_encrypt.

.PP

.I des_random_key

returns a random key that is made of a combination of process id,

time and an increasing counter.

.PP

Before a des key can be used it is converted into a

.I des_key_schedule

via the

.I des_set_key

routine.

If the

.I des_check_key

flag is non-zero,

.I des_set_key

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.

.PP

.I des_key_sched

is another name for the

.I des_set_key

function.

.PP

The following routines mostly operate on an input and output stream of

.I des_cblock's.

.PP

.I des_ecb_encrypt

is the basic DES encryption routine that encrypts or decrypts a single 8-byte

.I des_cblock

in

.I electronic code book

mode.

It always transforms the input data, pointed to by

.I input,

into the output data,

pointed to by the

.I output

argument.

If the

.I encrypt

argument is non-zero (DES_ENCRYPT),

the

.I input

(cleartext) is encrypted in to the

.I output

(ciphertext) using the key_schedule specified by the

.I schedule

argument,

previously set via

.I des_set_key.

If

.I encrypt

is zero (DES_DECRYPT),

the

.I input

(now ciphertext)

is decrypted into the

.I output

(now cleartext).

Input and output may overlap.

No meaningful value is returned.

.PP

.I des_ecb3_encrypt

encrypts/decrypts the

.I input

block by using triple ecb DES encryption.

This involves encrypting the input with 

.I ks1,

decryption with the key schedule

.I ks2,

and then encryption with the first again.

This routine greatly reduces the chances of brute force breaking of

DES and has the advantage of if

.I ks1

and

.I ks2

are the same, it is equivalent to just encryption using ecb mode and

.I ks1

as the key.

.PP

.I des_cbc_encrypt

encrypts/decrypts using the

.I cipher-block-chaining

mode of DES.

If the

.I encrypt

argument is non-zero,

the routine cipher-block-chain encrypts the cleartext data pointed to by the

.I input

argument into the ciphertext pointed to by the

.I output

argument,

using the key schedule provided by the

.I schedule

argument,

and initialisation vector provided by the

.I ivec

argument.

If the

.I 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.

To make multiple cbc encrypt calls on a large amount of data appear to

be one 

.I des_cbc_encrypt

call, the

.I ivec

of subsequent calls should be the last 8 bytes of the output.

.PP

.I des_3cbc_encrypt

encrypts/decrypts the

.I input

block by using triple cbc DES encryption.

This involves encrypting the input with key schedule

.I ks1,

decryption with the key schedule

.I ks2,

and then encryption with the first again.

2 initialisation vectors are required,

.I ivec1

and

.I ivec2.

Unlike

.I des_cbc_encrypt,

these initialisation vectors are modified by the subroutine.

This routine greatly reduces the chances of brute force breaking of

DES and has the advantage of if

.I ks1

and

.I ks2

are the same, it is equivalent to just encryption using cbc mode and

.I ks1

as the key.

.PP

.I des_pcbc_encrypt

encrypt/decrypts using a modified block chaining mode.

It provides better error propagation characteristics than cbc

encryption.

.PP

.I 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.

.PP

.I des_ofb_encrypt

encrypt 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.

.PP

.I des_cbc_cksum

produces an 8 byte checksum based on the input stream (via cbc encryption).

The last 4 bytes of the checksum is returned and the complete 8 bytes is

placed in

.I output.

.PP

.I des_quad_cksum

returns a 4 byte checksum from the input bytes.

The algorithm can be iterated over the input,

depending on

.I out_count,

1, 2, 3 or 4 times.

If

.I output

is non-NULL,

the 8 bytes generated by each pass are written into

.I output.

.PP

.I des_enc_write

is used to write

.I len

bytes

to file descriptor

.I fd

from buffer

.I buf.

The data is encrypted via

.I pcbc_encrypt

(default) using

.I sched

for the key and

.I iv

as a starting vector.

The actual data send down

.I 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.

.PP

.I des_enc_read

is used to read

.I len

bytes

from file descriptor

.I fd

into buffer

.I buf.

The data being read from

.I fd

is assumed to have come from

.I des_enc_write

and is decrypted using

.I sched

for the key schedule and

.I iv

for the initial vector.

The

.I des_enc_read/des_enc_write

pair can be used to read/write to files, pipes and sockets.

I have used them in implementing a version of rlogin in which all

data is encrypted.

.PP

.I des_rw_mode

is used to specify the encryption mode to use with 

.I des_enc_read

and 

.I des_end_write.

If set to

.I DES_PCBC_MODE

(the default), des_pcbc_encrypt is used.

If set to

.I DES_CBC_MODE

des_cbc_encrypt is used.

These two routines and the variable are not part of the normal MIT library.

.PP

.I des_set_odd_parity

sets the parity of the passed

.I key

to odd.  This routine is not part of the standard MIT library.

.PP

.I des_is_weak_key

returns 1 is the passed key is a weak key (pick again :-),

0 if it is ok.

This routine is not part of the standard MIT library.

.PP

.I crypt

is a replacement for the normal system crypt.

It is much faster than the system crypt.

.PP

.SH FILES

/usr/include/des.h

.br

/usr/lib/libdes.a

.PP

The encryption routines have been tested on 16bit, 32bit and 64bit

machines of various endian and even works under VMS.

.PP

.SH BUGS

.PP

If you think this manual is sparse,

read the des_crypt(3) manual from the MIT kerberos (or bones outside

of the USA) distribution.

.PP

.I des_cfb_encrypt

and

.I 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!

.PP

.I des_read_pw_string

is the most machine/OS dependent function and normally generates the

most problems when porting this code.

.PP

.I des_string_to_key

is probably different from the MIT version since there are lots

of fun ways to implement one-way encryption of a text string.

.PP

The routines are optimised for 32 bit machines and so are not efficient

on IBM PCs.

.PP

NOTE: extensive work has been done on this library since this document

was origionally written.  Please try to read des.doc from the libdes

distribution since it is far more upto date and documents more of the

functions.  Libdes is now also being shipped as part of SSLeay, a

general cryptographic library that amonst other things implements

netscapes SSL protocoll.  The most recent version can be found in

SSLeay distributions.

.SH AUTHOR

Eric Young (eay@cryptsoft.com)