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+.TH DES 1 
+.SH NAME
+des - encrypt or decrypt data using Data Encryption Standard
+.SH SYNOPSIS
+.B des
+(
+.B \-e
+|
+.B \-E
+) | (
+.B \-d
+|
+.B \-D
+) | (
+.B \-\fR[\fPcC\fR][\fPckname\fR]\fP
+) |
+[
+.B \-b3hfs
+] [
+.B \-k
+.I key
+]
+] [
+.B \-u\fR[\fIuuname\fR]
+[
+.I input-file
+[
+.I output-file
+] ]
+.SH DESCRIPTION
+.B des
+encrypts and decrypts data using the
+Data Encryption Standard algorithm.
+One of
+.B \-e, \-E
+(for encrypt) or
+.B \-d, \-D
+(for decrypt) must be specified.
+It is also possible to use
+.B \-c
+or
+.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
+Two standard encryption modes are supported by the
+.B des
+program, Cipher Block Chaining (the default) and Electronic Code Book
+(specified with
+.B \-b
+).
+.LP
+The key used for the DES
+algorithm is obtained by prompting the user unless the
+.B `\-k
+.I key'
+option is given.
+If the key is an argument to the
+.B des
+command, it is potentially visible to users executing
+.BR ps (1)
+or a derivative.  To minimise this possibility,
+.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
+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
+or
+.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
+command reads from standard input unless
+.I input-file
+is specified and writes to standard output unless
+.I output-file
+is given.
+.SH OPTIONS
+.TP
+.B \-b
+Select ECB
+(eight bytes at a time) encryption mode.
+.TP
+.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.
+If the key is less than 8 characters long, the flag has no effect.
+.TP
+.B \-e
+Encrypt data using an 8 byte key in a manner compatible with sunOS
+des(1).
+.TP
+.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
+Generate a 16 character hexadecimal cbc checksum and output this to
+stderr.
+If a filename was specified after the
+.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
+A cbc checksum is generated in the same manner as described for the
+.B \-c
+option but the DES key is generated in the same manner as used for the
+.B \-E
+and
+.B \-D
+options
+.TP
+.B \-f
+Does nothing - allowed for compatibility with sunOS des(1) command.
+.TP
+.B \-s
+Does nothing - allowed for compatibility with sunOS des(1) command.
+.TP
+.B "\-k \fIkey\fP"
+Use the encryption 
+.I key
+specified.
+.TP
+.B "\-h"
+The
+.I key
+is assumed to be a 16 character hexadecimal number.
+If the
+.B "\-3"
+option is used the key is assumed to be a 32 character hexadecimal
+number.
+.TP
+.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
+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
+will be embedded in the header.
+.SH SEE ALSO
+.B ps (1)
+.B des_crypt(3)
+.SH BUGS
+.LP
+The problem with using the
+.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
+and
+.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
+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
+to uuencode the data before it is send to the VMS system.
+.SH AUTHOR
+.LP
+Eric Young (eay@cryptsoft.com)