Introduction to digital recovery and digital preservation.

1. INTRODUCTION
TO TIME TRAVEL
-OR-
1
HOW TO SEND YOUR FILES TO THE FUTURE

2. TIME TRAVEL:
A MODIFIED DEFINITION
2
COMMUNICATION
ACROSS TIME AND SPACE

3. 3
A BRIEF HISTORY
OF TIME TRAVEL

4. RECENT ATTEMPTS AT TIME TRAVEL

5. INFORMATION PRESERVATION
A long time ago…
Today
Analog
The Future!
Today
Digital
5
REQUIRES DIGITAL PRESERVATION

6. WHAT DOES ‘DIGITAL’
ACTUALLY MEAN?
6
(FOR STORAGE)

7. MAGNETIC MEDIA: HARD DRIVES
7
Peaks = 1s
Troughs = 0s

8. 8
SOLID STATE MEDIA: SD CARDS

9. 9
OPTICAL MEDIA: CDS

10. A QUESTION OF
REPRESENTATION
=
“I am the wisest
man alive, for I
know one
thing, and that
is that I know
nothing.”
-Plato
10
=
00100010010010010010000001100001011
01101001000000111010001101000011001
01001000000111011101101001011100110
11001010111001101110100001000000110
11010110000101101110001000000110000
10110110001101001011101100110010100
10110000100000011001100110111101110
01000100000010010010010000001101011
01101110011011110111011100100000011
01111011011100110010100100000011101
00011010000110100101101110011001110
01011000010000001100001011011100110
01000010000001110100011010000110000
10111010000100000011010010111001100
10000001110100011010000110000101110
10000100000010010010010000001101011
01101110011011110111011100100000011
01110011011110111010001101000011010
01011011100110011100101110001000100
00011010000101000101101010100000110
1100011000010111010001101111

11. BIT ROT:
THE DEGRADATION OF BITS
OVER TIME
"I am the wisest
man"alive, fob I know one
thing, and that is that I onow
nothing."
-Plato
-Plato
Original Text
3 Bits Corrupted
11
“I am the wisest man
alive, for I know one
thing, and that is that I
know nothing.”

12. BIT
LOSS
& DIGITAL
PHOTOS
12
Images from Melanie Willhide‟s
“to Adrian Rodreguez with love”
http://www.vonlintel.com/MelanieWillhide.html

13. ALMOST LOST
BBC Domesday Project 1986
13
NASA images from first Lunar
Orbiter 1966

14. 14
DOMESDAY PROJECT

15. DIGITAL PRESERVATION
STRATEGIES
Format Choice
Documentation
Migration
Emulation
Hashing/checksums
File Identification
15
1.
2.
3.
4.
5.
6.

16. 1. FORMAT CHOICE
Hardware
16
Software

17. NDIIPP
17
http://www.digitalpreservation.gov/formats/index.shtml

18. http://www.digitalpreservation.gov/
18
THE LIBRARY OF CONGRESS:
DIGITAL PRESERVATION

19. 2. DOCUMENTATION & METADATA
• File Type
Word Doc
• Software Version
MS Word 2010
File Name
File Size
Number of Words
Total Editing Time
Creation Date
Last Modified
Last Printed
User Name
19
•
•
•
•
•
•
•
•

20. 3. MIGRATION
20
• The transfer of
a bit stream
(the 1s and 0s)
from one
medium to
another.

21. 21
FINDING THE HARDWARE

22. MIGRATION
Similar to
photocopying –
including the
imperfections.
22
Data can be lost or
corrupted in the
transfer.

23. WRITE BLOCKERS
• Prevents
inadvertently
overwriting digital
information.
23
• Allows „read‟
commands to
pass, blocks „write‟
commands.

24. 4. EMULATION
Creates an
environment that
„tricks‟ the software
into functioning as if
it was in its original
computing
environment.
24
Similar to impersonation.

25. EMULATION &
THE GAMING COMMUNITY
"The Old Version Flickers More": Digital Preservation from the User's
Perspective
25
http://archivists.metapress.com/content/1765364485n41800/

26. https://archive.org/details/historicalsoftware
26
BROWSER BASED EMULATION

27. 5. HASHING/CHECKSUMS
How they work:
An algorithms „reads‟ a digital object and, based upon the 1s
and 0s that make up that object, produces a unique alphanumeric string of characters that represent it.
27
What that means:
Checksums are very effective tools in determining if a digital
object has been corrupted (assuming you have the original
checksum to compare it to).

28. HASHING
MD5 Hash
Corrupted File
FD7D5993
062D270F
482E00BD
E64D35FE
461D5E8093
B94401EAF
12E442CEA
B908
28
Original File

29. http://download.cnet.com/MD5-SHA-Checksum-Utility/3000-2092_410911445.html
29
HASHING

30. 30
HASHING IN TWO STEPS

31. IDENTIFYING MYSTERY FILES
.hqx? .mkv? .ape?
31
You have to identify what a file is in order to figure
out what software can render it. But how?

32. 6. FILE IDENTIFICATION
32
Step 1: Google the file extension

33. 33
IDENTIFYING MYSTERY FILES

34. IDENTIFYING MYSTERY FILES
Step 1: Google the file extension
34
Step 2: If step 1 fails, use DROID

35. http://www.nationalarchives.gov.uk/information-management/our-services/dc-file-profiling-tool.htm
35
Digital Record Object Identification

36. IDENTIFYING MYSTERY FILES
Step 1: Google the file extension
Step 2: If step 1 fails, use DROID
36
Step 3: If step 2 fails, open it in a hex editor

37. HXD HEX EDITOR
37
http://download.cnet.com/HxD-Hex-Editor/3000-2352_4-10891068.html

38. 38
HEX EDITOR VIEW

39. FILE SIGNATURES/MAGIC NUMBERS
• Every file type has a digital „finger print‟
near the beginning of its code, sometimes
called a „signature‟ or „magic number‟.
39
• In a hex editor, you can read the
hexadecimal notation of the file and
identify its magic number, then look up
that number to identify the file type.

40. WIKIPEDIA’S FILE SIGNATURE LIST
40
http://en.wikipedia.org/wiki/List_of_file_signatures

41. IF YOU HAVE QUESTIONS
ABOUT DIGITAL PRESERVATION
41
THE LIBRARY IS HERE TO HELP

42. Questions?
Shea Swauger
Data Management Librarian
Morgan Library, 210E
shea.swauger@gmail.com
42
This presentation is available at http://www.slideshare.net/SheaSwauger