Mercurial > public > m209
changeset 60:0a3e4bc49118
Added docs for the decrypt sub-command.
author | Brian Neal <bgneal@gmail.com> |
---|---|
date | Fri, 12 Jul 2013 14:17:02 -0500 (2013-07-12) |
parents | 6acd17898381 |
children | 35b5eb90f5ad |
files | docs/commandline.rst |
diffstat | 1 files changed, 84 insertions(+), 2 deletions(-) [+] |
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--- a/docs/commandline.rst Wed Jul 10 21:33:03 2013 -0500 +++ b/docs/commandline.rst Fri Jul 12 14:17:02 2013 -0500 @@ -191,8 +191,9 @@ Likewise with punctuation. To make encryption more convenient, the ``m209`` program will accept spaces and automatically convert them to the letter ``Z``. Lowercase letters will automatically be converted to uppercase. All - other characters will produce an error. This applies to both text read on - the command-line with the ``-t`` option and text read from files (``-f``). + other characters will be silently dropped from the input. This applies to + both text read on the command-line with the ``-t`` option and text read from + files (``-f``). Encrypt examples ++++++++++++++++ @@ -201,6 +202,7 @@ random encryption parameters:: $ m209 encrypt -t "Rendezvous at zero seven thirty" + BBEPH SSLBY RKHWO OBAJB VYQEQ NJHGV FWRCJ UZHMB PXXXX BBEPH SSLBY To save the encrypted text to a file:: @@ -214,3 +216,83 @@ $ cat message.txt | m209 enc --file=- -k SU -e ZQGMFO -s A + +Decrypt sub-command +------------------- + +``decrypt``, or ``dec``, is the sub-command used to decrypt text. To get help +on the ``decrypt`` command, type the following:: + + $ m209 decrypt --help + usage: m209 decrypt [-h] [-z KEY_FILE] [-f FILE] [-t TEXT] + + Decyrpt text from a file or command-line + + optional arguments: + -h, --help show this help message and exit + -z KEY_FILE, --key-file KEY_FILE + path to key list file [default: m209keys.cfg] + -f FILE, --file FILE path to ciphertext file or - for stdin + -t TEXT, --text TEXT text string to decrypt + + Either the -f/--file or -t/--text arguments must be supplied + +The options to the ``decrypt`` command are described below. + +``-z`` or ``--key-file`` + This option names the key list file. If not given, the default of + ``m209keys.cfg`` is used. + +``-t`` or ``--file`` + This option specifies the file that contains the text to decrypt. If the + filename is given as ``-`` then input is read directly from ``stdin``. Note + that either this option or the ``-t`` option must be specified, but not + both. + +``-t`` or ``--text`` + This option specifies the text to decrypt on the command-line. Depending + upon your system, you'll probably have to quote or escape your text. Note + that you must either specify this option or the ``-f`` option, but not both. + +.. NOTE:: + + The first and last 2 groups of an encrypted message contain the information + needed to decrypt the message: the system indicator, the external message + indicator, and the key list indicator. If the key list file given to the + decrypt command does not contain the key list used to encrypt the message, + then the message cannot be decrypted and an error message will be displayed. + +Decrypt examples +++++++++++++++++ + +To decrypt a simple string on the command-line using the default key file:: + + $ m209 decrypt -t "BBEPH SSLBY RKHWO OBAJB VYQEQ NJHGV FWRCJ UZHMB PXXXX BBEPH SSLBY" + RENDE VOUS AT ERO SEVEN THIRTYXSJQ + +To save the decrypted text to a file:: + + $ m209 decrypt -t "BBEPH SSLBY RKHWO OBAJB VYQEQ NJHGV FWRCJ UZHMB PXXXX BBEPH SSLBY" > msg.txt + +To read the contents of a file and decrypt it, saving it to a new file:: + + $ m209 dec -f secret.txt > msg.txt + +To decrypt from ``stdin``:: + + $ cat secret.txt | m209 dec -f - + RENDE VOUS AT ERO SEVEN THIRTYXSJQ + + +.. NOTE:: + + In this example, the last group of the encrypted message only has one + letter. It was padded out to five letters with ``X``'s by the encryption + process, and thus four "garbage" letters appear at the end in the decrypted + output. + + Note also that the ``Z`` in ``RENDEZVOUS`` and ``ZERO`` were converted to + spaces by the decrypt process. + + In both of these cases the operator would have to "fix up" the message + before passing it up the chain of command.