Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Think of it as a spell checker that insults you, as well.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.

user:
pass:
register,


     

Sudocrypto

Those puzzles might be ubiquitous for a non-obvious reason
 
(+2, -2)
  [vote for,
against]

A big problem with sending encrypted messages is managing the keys required to decrypt them. There are various solutions to this problem, here’s a fun one.

A solved sudoku puzzle consists of 81 decimal digits. Why not use this as a crypto key? You could even send the unsolved puzzle right along with the encrypted message. The recipient solves the puzzle, punches the digits into a program and voila.

A big limitation, of course, is anyone who can solve the puzzle can read the message. As long as your arch-enemy is stupid or lazy, this might well be enough.

Can we improve this? Sure…

First, the number of possible sudoku puzzles is roughly equivalent to the key space of a 72 bit crypto key. That is not good at all. Instead of using the solution as a key directly, we could use it as a numeric index into a large database of pre-calculated keys. The keys themselves could be as large as necessary to resist direct cryptographic attack. The key database could be transmitted ahead of time, perhaps on a portable disk, and thus acts somewhat like a “one time pad.”

Second, don’t transmit the puzzle with the message. Pre-arrange to find the correct puzzle in a known public location. Perhaps if we could get a series of these published somewhere, we could use a different one for each day you transmit a message...

...hey, wait a sec….I wonder if this is baked?

krelnik, May 02 2007

WIkipedia: Mathematics of Sudoku http://en.wikipedia...thematics_of_Sudoku
[jutta, May 02 2007]

Please log in.
If you're not logged in, you can see what this page looks like, but you will not be able to add anything.
Short name, e.g., Bob's Coffee
Destination URL. E.g., https://www.coffee.com/
Description (displayed with the short name and URL.)






       I'm not sure I get your point, bigsleep. I'm not proposing anything new cryptographically, just a novel way to manage keys that involves puzzles. This method would work equally well (if at all) for any chosen crypto algorithm.
krelnik, May 02 2007
  


 

back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle