# Posts Tagged: cryptography

• web

## Lists 2010 : StackExchange sites

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One of the trends of 2010 was the proliferation of StackExchange sites. I guess by now most of us visit MathOverflow along with the arXiv daily. But, there are plenty of other StackExchange sites around that may be of interest to the mathematics-community : Mathematics somewhat less high-brow than MathO. Physics still in the beta-phase… Read more »

• games, number theory

## On2 : transfinite number hacking

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Surely Georg Cantor’s transfinite ordinal numbers do not have a real-life importance? Well, think again.

• stories

## return of the cat ceilidh

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I couldn’t believe my eyes. I was watching an episode of numb3rs, ‘undercurrents’ to be precise, and there it was, circled in the middle of the blackboard, CEILIDH, together with some of the key-exchange maps around it… Only, the plot doesn’t involve any tori-crypto… okay, there is an I-Ching-coded-tattoo which turns out to be a… Read more »

• stories

## now what?

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You may not have noticed, but the really hard work was done behind the scenes, resurrecting about 300 old posts (some of them hidden by giving them ‘private’-status). Ive only deleted about 10 posts with little or no content and am sorry I’ve self-destructed about 20-30 hectic posts over the years by pressing the ‘delete… Read more »

• featured

## the crypto lattice

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Last time we have seen that tori are dual (via their group of characters) to lattices with a Galois action. In particular, the Weil descent torus $R_n=R^1_{\mathbb{F}_{p^n}/\mathbb{F}_p} \mathbb{G}_m$ corresponds to the permutation lattices $R_n^* = \mathbb{Z}[x]/(x^n-1)$. The action of the generator $\sigma$ (the Frobenius) of the Galois group $Gal(\mathbb{F}_{p^n}/\mathbb{F}_p)$ acts on… Read more »

• featured

## Weil descent

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A classic Andre Weil-tale is his narrow escape from being shot as a Russian spy The war was a disaster for Weil who was a conscientious objector and so wished to avoid military service. He fled to Finland, to visit Rolf Nevanlinna, as soon as war was declared. This was an attempt to avoid being… Read more »

• featured

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• featured

## micro-sudoku

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One cannot fight fashion… Following ones own research interest is a pretty frustrating activity. Not only does it take forever to get a paper refereed but then you have to motivate why you do these things and what their relevance is to other subjects. On the other hand, following fashion seems to be motivation enough… Read more »