Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister
 
PerlMonks  

Re: encryption (chi-squared test)

by gumby (Scribe)
on Jun 20, 2002 at 12:40 UTC ( #175986=note: print w/ replies, xml ) Need Help??


in reply to encryption

An alternative, of course, is to use a statistical method: use the chi-squared test (see Mathworld).

Let F_a(x) be the frequency of some letter, x, in you're alphabet, and let F_m(x) be the frequency of some letter, x, in the message. Now, for all 0 <= s <= 25 calculate for each letter, x, in your alphabet the sum of the squares of F_m((x + s)(mod 26)) / F_a(x). The value of s for which this obtains a minimum is the shift used to encipher the message.


Comment on Re: encryption (chi-squared test)

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://175986]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others cooling their heels in the Monastery: (11)
As of 2014-10-21 14:03 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    For retirement, I am banking on:










    Results (103 votes), past polls