Manpage of ppdncrypt
Section: User Commands (1)
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ppdncrypt - encrypt data for ppdd without kernel support
This program allows you to encrypt data in a such a way that it is acceptable
as a host file for ppdd. Extra functionality (including an interface to pgp)
makes it useful also as a backup tool. As it is intended to be used only with
ppdd it makes use of the fact that the size of the data it is dealing with
is a multiple of 1024 bytes. It is not a general purpose encryption tool.
The program operates in two modes, ppdd and conventional.
In ppdd mode the
program makes no use of the first 1024 bytes of the input file; the first
1024 bytes of the output file contain normal ppdd control information,
including the keys, encrypted with a key derived from the pass phrase.
In conventional mode the first 1024 bytes of the input file are included
in the output and an additional 1024 byte block is included at the start
of the output file to contain the ppdd control information. A file
encrypted this way is not suitable for use directly as a ppdd host file
but can be used as input into ppdecrypt. This is a suitable way to back
up ppdd host files.
In ppdd mode the program can be run so as to overwrite the original file,
thus providing an encrypt in place facility. Unlike that offered by ppddinit,
it does not require kernel support.
The program will ask for a pass phrase to use for encrypting the data. There
is also the possibility to select weaker random key generation.
Please see ppdd(1) and ppddinit(1) for more information on random key
generation and the choice of pass phrases.
The program provides an interface to pgp so as to enable backups to be made
using a public key. This type of operation will produce an output file which
is suitable only as input to ppdecrypt in pgp mode. The output is totally
unsuitable for use as a ppdd host file. Note that pgp must have already been
installed correctly. A userid of "backup" must exist on the public keyrung.
In pgp mode there is the choice of ppdd or conventional mode. This determines
whether the first 1024 bytes of the input file is included in the output file
or not. In ppdd mode the first 1024 bytes are excluded. The reasons why you
may want to exclude this block of data from the backup is explained in the
If any invalid combination of switches and arguments is used the program
displays a primitive help message. The number of arguments depends on the
In normal file copying mode the following are valid:
ppdncrypt input_file output_file
ppdncrypt -c input_file output_file
ppdncrypt -w input_file output_file
ppdncrypt -cw input_file output_file
-c means preserve the first 1024 bytes
-w means use weaker random key generation
In all the above case a device (e.g. /dev/hda3) could substitute for a file,
either as input or output or both,
but the output device must be at least as large as the input. In the case of
conventional encryption an extra 1024 bytes are needed.
In overwrite mode the following are valid:
ppdncrypt -o file_or_device
ppdncrypt -ow file_or_device
In pgp mode the following are valid:
ppdncrypt -p input_file_or_device output_file
ppdncrypt -pc input_file_or_device output_file
The program returns 0 if everything worked as expected.
The program returns 1 if anything has gone wrong.
All ppdd utilities display fairly meaningful errors (mostly on stderr).
In all cases the errors have a unique error number to help locate the
problem in the source code. If an error message is not clear then best
source of explanation at this stage is the source itself.
The program does not use any environment variables.
Files (and devices) are specified as arguments.
(c) 1999 Allan Latham - version 0.9
- RETURN VALUE
- SEE ALSO
This document was created by
using the manual pages.
Time: 16:39:32 GMT, September 14, 1999