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### Using paper as apocalyptic-resilient backup storage ### |
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Today, out of the blue, I was pondering about paper. You know, this cellulose |
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based thingy that Chinese people came up with back in the good old days of |
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the Han dynasty. Since these how remote times, humanity relied on paper for |
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storing information and, as thousands of years demonstrated, paper proved to |
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be an excellent long-time medium. |
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Nowadays we use diskettes, magnetic drives, flash memories and CD/DVD |
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discs... But neither of these comes anywhere close to paper's longevity and |
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resilience. Any serious magnetic disturbance will flush out data from most of |
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our computers, mild UV exposure will erase the content of our writeable |
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CD/DVDs, and in any case - all of these modern storage contraptions are |
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unlikely to be readable in 50-100 years. |
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So I thought - wouldn't it be nice to use paper as a storage for binary data? |
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After some quick research I found out (unsurprisingly) that I am not the |
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first to have come up with such idea. There are at least three software |
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packages out there that are dedicated to exactly that: |
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* PaperDisk, a commercial offering from Cobblestone Software (Win 3.1, 9x) |
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* PaperBack, an open-source software by Michael Mohr (Windows only, sadly) |
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* Optar, an open-source software by Karel Kulhavy (POSIX) |
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All these solutions share one big limitation, though: paper has a relatively |
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low data density, which translates to low data capacity. Apparently, it is |
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realistic to expect about 300-500K of storage on a single A4 sheet. This is |
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not much, but still - if we own some data that has a high value-per-byte |
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ratio, such backup could be an excellent long-term storage strategy. |
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Before using paper-based backups, one needs to think about a major (and |
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easily overlooked) potential problem - let's assume our paper backup sheet |
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survives 3000 years, and in some dystopian future a sentient race discovers |
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it. How would they know how to decode it? Surely they will not have access |
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to a PC running Windows 3.11 with proper software. Without going to such |
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extreme scenario, this problem might just as well apply to the paper backup |
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author itself, 20 years later: "I encoded important data on this A4 sheet |
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20 years ago using some exotic software - how do I decode it now?. |
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For the above reason, it may be safer (although much less efficient) to opt |
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for a paper-based backup solution that prints data in a way that a human |
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could easily understand and decode. Writing data encoded as a suit of letters |
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comes naturally to mind: after all, it is what we do since 6000 years now, |
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with very good results. Binary data could therefore be encoded in a BASE-32 |
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"alphabet", composed of the most recognizeable latin symbols. Instructions |
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how to decode it would be short enough to be written on the margin of the |
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sheet. On a single A4 sheet it is possible to fit comfortably 10'000 |
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characters. When encoded with a BASE-32 scheme, this translates to a useable |
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storage of 6 KiB. It is much less than with sophisticated methods used by the |
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dedicated softwares listed before, but it has the advantage of being trivial |
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to decode either by hand, or using any kind of OCR software - now or in the |
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future. |
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Attached to this article is a copy of the latest (as of February 2019) |
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PaperBack source code, the shareware PaperDisk 1.0 release (1997), an |
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extremely interesting white paper on the subject from Cobblestone Software, |
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as well as the source code and website copy of Optar (2007). |
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=== Attachments ========================================== |
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optar.pdf |
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optar.tgz |
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paperbak-1.10.src.zip |
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paperdisk v1.0 shareware.zip |
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paperdisk white paper.pdf |
