#7123: cryptanalysis of the shift cipher
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Reporter: mvngu | Owner: somebody
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.1.3
Component: cryptography | Keywords:
Work_issues: | Author: Minh Van Nguyen
Reviewer: | Merged:
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Comment(by rbeezer):
Replying to [comment:5 mvngu]:
Minh,
That's pretty much exactly what I had in mind. And I'd forgotten to
mention the Army Field Manual. ;-)
The chi-square statistic does look like a likely candidate. I'd also
thought of taking the sum of the squared differences between the two
distributions (the candidate decrypt frequency vs. the characteristic
frequency). Something makes me think that they may be equivalent, or one
is clearly superior, but I don't have a reference, nor have I checked. If
they are different, then implementing both and testing one versus the
other could be a good project for a user. In any event, I think I'd code
a choice of the function that "scores" each candidate decrypt, either with
a default keyword, or in the extreme, an option to pass in your own
function (assuming two arguments, the decrypt and the characteristic
frequency).
OK, a bit brief, but I'm trying to beat the Sage infrastructure cutover in
25 minutes. ;-)
Rob
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7123#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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