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Updated Backups (markdown)

Dominik Schürmann 2016-01-05 19:50:10 +01:00
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Backups.md

@ -16,7 +16,7 @@ This is work in progress...
## Design decisions
* Using only upper case letters, no lower case letters and no numbers
* Using lower case and upper case makes it much more difficult to recall the characters from short term memory. Consider someone reading them aloud, it is required to say for every letter if it's upper or lower case. Memorizing things in short term memory works similar to reading something aloud, which makes the mixed upper/lower case backup codes double as difficult to remember than only one case backup codes.
* Using mixed upper and lower case makes it much more difficult to recall the characters from short term memory. Consider someone reading them aloud, it is required to say for every letter if it's upper or lower case. Memorizing things in short term memory works similar to reading something aloud, which makes the mixed upper/lower case backup codes double as difficult to remember than only one case backup codes.
* Numbers would increase the alphabet by only 10 characters, the length of the backup code would be only 2 characters shorter to achieve the same security.
* If numbers would be included, we should use lowercase to allow better differentiation between lower and upper case. Because we don't include them we could stay with uppercase letters.
* Possible combinations are: 26^24 = 2^112.8
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* 1986, Richard Schweickert, Brian Boruff: Short-Term Memory Capacity: Magic Number or Magic Spell?
* 1994, George A. Miller: The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information
* [2000, Nelson Cowan: The magical number 4 in short-term memory: A reconsideration of mental storage capacity](http://journals.cambridge.org/article_S0140525X01373922)
* [On the Memorability of System-generated PINs: Can Chunking Help?](http://lersse-dl.ece.ubc.ca/record/304/files/soups2015-final110.pdf)
this is long term:
* [On the Memorability of System-generated PINs: Can Chunking Help?](http://lersse-dl.ece.ubc.ca/record/304/files/soups2015-final110.pdf)
* Applying Chunking Theory in Organizational Password Guidelines