Archimedes Palimpsest MD5 Read Me File

WHAT THE MD5 FILES ARE

Each image and XML data file in the Archimedes Palimpsest Digital
Release is accompanied by an MD5 checksum file.  This file is used to
check the integrity and authenticity of the corresponding data file.
It has a name that, except for the file extension, is identical to the
data file it accompanies.  For example, the TIFF image file

        * 069r-068v_Arch09r_Heiberg_ultraviolet_stitch_beta.tif

is accompanied by the MD5 file

        * 069r-068v_Arch09r_Heiberg_ultraviolet_stitch_beta.md5

The content of this file is (all on one line):

f11dc15e9ac2ed66c94fd853965d25dd \
       069r-068v_Arch09r_Heiberg_ultraviolet_stitch_beta.tif

If a single byte in the input file is changed, then it will have a
different MD5 checksum.

HOW TO USE AN MD5 CHECKSUM

A file's integrity is checked by running an MD5 utility on an input
file and comparing the generated checksum against the checksum stored
in its MD5 file.  Common MD5 utilities are 'md5' and 'md5sum'.  A list
of MD5 utilities is given below.

The following example shows a checksum comparison using the
command-line utility 'md5' on the Mac OS X operating system.

This directory listing shows the MD5 and TIFF files.

  [095v-090r]>ls
  095v-090r_Arch43v_Sinar_pseudo_no-veil.md5
  095v-090r_Arch43v_Sinar_pseudo_no-veil.tif

The cat command outputs the content of a file, in this case the MD5,
to the screen.

  [095v-090r]>cat 095v-090r_Arch43v_Sinar_pseudo_no-veil.md5 
  e02df965870fcbb2a247d10827cec44d 095v-090r_Arch43v_Sinar_pseudo_no-veil.tif

The MD5 file contains two values: the 32-character checksum and the
name of the input file.  

The md5 utility is run on the TIFF file to generate a new checksum:

  [095v-090r]>md5 -r 095v-090r_Arch43v_Sinar_pseudo_no-veil.tif
  e02df965870fcbb2a247d10827cec44d 095v-090r_Arch43v_Sinar_pseudo_no-veil.tif

An comparison of the MD5 file with the checksum output shows the two
checksums are identical.  (The '-r' flag tells md5 to format the
checksum in this, more or less, standard form.)

MD5 UTILITIES

Most MD5 utilities are command-line tools that are run from a console,
like a DOS prompt or Unix terminal window.  Most allow you to generate
a checksum, as shown above, to compare visually to a stored checksum.

The following list of tools is for users' convenience.  These tools
have not been tested by the Archimedes Palimpsest Project and no
guarantee or endorsement is intended by this listing.

                               Windows
Graphical User Interface Tools

  * WinMD5
    http://www.blisstonia.com/software/WinMD5/

  * MD5 Summer
    http://www.md5summer.org/

Command-Line Tools

  * MD5sums for Windows
    http://www.pc-tools.net/win32/md5sums/

  * md5sum is also available with the Cygwin Windows Linux utilities
    http://www.cygwin.com/

                               Mac OS X
Command-Line Tools

  * md5 (Console tool)
    Included 

The APDR MD5 files are in a common format: a single line with checksum
followed by a space and then the filename.  The format of different
utilities' output depends on the tool and how it is used.  It cannot
be guaranteed that the APDR files will conform to the format expected
by automated verification tools.


MORE ABOUT MD5

The MD5 file is a checksum that contains a 32-character hash value
that can be used to confirm the integrity of the corresponding TIFF
file.  The details of the one-way MD5 hash algorithm is described in
the Internet standard RFC 1321.  This document is included here as
rfc1321.txt.  It is also available at:

        * http://www.ietf.org/rfc/rfc1321.txt
        * http://www.faqs.org/rfcs/rfc1321.html

In short, MD5 is one-way hash algorithm for generating a 32-character
value based on the byte structure of an input file.  This value has a
very low likelihood of being the same for any two input files.  

For the file 069r-068v_Arch09r_Heiberg_ultraviolet_stitch_beta.tif
the MD5 hash value is

        * f11dc15e9ac2ed66c94fd853965d25dd