DES(1)                                                                 DES(1)



NAME
  des - encrypt or decrypt data using Data Encryption Standard

SYNOPSIS
  ddeess ( --ee | --EE ) | ( --dd | --DD ) | ( --[ccCC][cckknnaammee] ) | [ --bb33hhffss ] [ --kk _k_e_y ] ]
  [ --uu[_u_u_n_a_m_e] [ _i_n_p_u_t_-_f_i_l_e [ _o_u_t_p_u_t_-_f_i_l_e ] ]

DESCRIPTION
  ddeess encrypts and decrypts data using the Data Encryption Standard algo-
  rithm.  One of --ee,, --EE (for encrypt) or --dd,, --DD (for decrypt) must be speci-
  fied.  It is also possible to use --cc or --CC in conjunction or instead of the
  a encrypt/decrypt option to generate a 16 character hexadecimal checksum,
  generated via the _d_e_s___c_b_c___c_k_s_u_m_.

  Two standard encryption modes are supported by the ddeess program, Cipher
  Block Chaining (the default) and Electronic Code Book (specified with --bb ).

  The key used for the DES algorithm is obtained by prompting the user unless
  the ``--kk _k_e_y_' option is given.  If the key is an argument to the ddeess com-
  mand, it is potentially visible to users executing ppss(1) or a derivative.
  To minimise this possibility, ddeess 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.

  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 --EE,, --DD,, --CC or --33 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.  ddeess command reads from standard input unless _i_n_p_u_t_-_f_i_l_e is speci-
  fied and writes to standard output unless _o_u_t_p_u_t_-_f_i_l_e is given.

OPTIONS

  --bb   Select ECB (eight bytes at a time) encryption mode.

  --33   Encrypt using triple encryption.  By default triple cbc encryption is
       used but if the --bb option is used then triple ecb encryption is per-
       formed.  If the key is less than 8 characters long, the flag has no
       effect.

  --ee   Encrypt data using an 8 byte key in a manner compatible with SunOS
       des(1).

  --EE   Encrypt data using a key of nearly unlimited length (1024 bytes).
       This will product a more secure encryption.

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

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

  --cc   Generate a 16 character hexadecimal cbc checksum and output this to
       stderr.  If a filename was specified after the --cc option, the checksum
       is output to that file.  The checksum is generated using a key gener-
       ated in a SunOS compatible manner.

  --CC   A cbc checksum is generated in the same manner as described for the --cc
       option but the DES key is generated in the same manner as used for the
       --EE and --DD options

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

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

  --kk _k_e_y
       Use the encryption _k_e_y specified.

  --hh   The _k_e_y is assumed to be a 16 character hexadecimal number.  If the --33
       option is used the key is assumed to be a 32 character hexadecimal
       number.

  --uu   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.

SEE ALSO
  ppss ((11)) ddeess__ccrryypptt((33))

BUGS

  The problem with using the --ee 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 nec-
  essary for a brute-force cryptographic attack.  My attempt to remove this
  problem is to add an alternative text-key to DES-key function.  This alter-
  native function (accessed via --EE,, --DD,, --SS and --33 ) uses DES to help generate
  the key.

  Be carefully when using the -u option.  Doing des -ud <filename> will not
  decrypt filename (the -u option will gobble the d option).

  The VMS operating system operates in a world where files are always a mul-
  tiple 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.

AUTHOR

  Eric Young (eay@mincom.oz.au or eay@psych.psy.uq.oz.au)