Cryptography where do I start?

Well I have always been interested in Cryptography. I have a few questions....

1. Where do I get started learning cyrptography besides books as I am tight on cash atm?

2. What kinds of maths are involved in cryptography?

The main reason I want to learn about cryptography is because it has always interested me and I would like to learn to decrypt encypted messages.

I wonder if it helps that I like to do those cryptograms in the newspapers lol.

Btw I also have a strong programming background if that helps.

Also I have been using google but I am not quite sure I am getting the maximum results I should be getting.

well google is a good way to start allways.
here is a link you will find helpfull http://world.std.com/~franl/crypto.html
their is a lot of reading material on this page to get you learning it also has a good explaination of RSA that you should read. http://world.std.com/~franl/crypto/rsa-guts.html

Wow lots of information on that page. Much more then what I found. Actually one of the sites I found is linked on this website. Thanks a bunch.

You're proably going to want to make a simple program, that rotates all the letters X positions, or somthing simmilar. Then you can work up to more complex code.
http://www.cr0.net:8040/code/crypto/ has some information too.

dude u have to read books as you are a newbie i suggest u to read william stallings book Cryptography is not only about mathematics only and cryptanalysis is not as easy as shown in movies.because encryption being used now a days are much complex and involve large number of stages.
so in order to be a expert u need through knowledge of encryption scheme.

Hi

General readers

Cryptography[1] is an interesting topic, the question is how
deep do you want to dive into it. If you want to satisfy
your curiosity on a playful level, the best thing is to
look at some easy-readers, as [2,3] and apply your knowledge
on newspapers and/or [3,4].

If you really want to follow a scientific approach to cryptography,
one of Riots links links to the free e-book by Menezes et el.[5],
which I can recommend as a starting point.

Mathematics

From a mathematical point of view, crytography starts with functions
and their domain and codomain space. Usually, only a subset of all
functions are used (the invertible ones), which simplifies the mathe-
matical description. This functional analysis can be as complicated as
you wish (Riemann Zeta functions, Lee-Yang (?), Elliptical curve cryptography, ...),
still the mathematical tools are the same.

Interdisciplinary and Enigma

Cryptography draws aspects from a lot of additional fields, like discrete
mathematics, number theory, statistics, combinatorics in addition with
linguistics, information theory and complexity theory ("computationally feasible
to solve"). All ingredients are substantially crucial in order to decrypt an
encrypted messsage. E.g. the polish mathematicians around 1938 wouldn't have
been able to decrypt the Enigma[6] messages, without knowing german, without
knowing the typical structure of military intelligence and without having
a pre-computer ("clock", later "bomba" (badly translated as "bombe")),
even though they had a copy of the Enigma machine.


Conclusion

You need to remember that encryption techniques used nowadays are simple
in its description from a mathematical point of view. Their security is
based on a immensely huge key-space, that cannot be simply reduced based
on the intrinsics (eg. products of prime numbers). To do serious work on
that requires knowledge on the level of a PhD in mathematics. Keep this
in mind.
Doing cryptography (or more accurate: Decryption of encrypted message on
a playful level) requires a smart head, good ideas and a lot of persistence!
By reading [5], you will quickly recognize which type you prefer. Have in
mind, that [5] really is just the very basics, compared to the state-of-the-art
cryptography that is done, e.g. in a military environment.

Cheers



[1] http://en.wikipedia.org/wiki/Cryptography
[2] http://www.und.edu/org/crypto/crypto...class/lessons/
[3] http://www.murky.org/cryptography/
[4] http://www.hackthissite.org
[5] http://www.cacr.math.uwaterloo.ca/hac/
[6] http://en.wikipedia.org/wiki/Enigma_machine

Well thank you very much. I am getting very good answers. And Yes this is only playful decryption and stuff. I am a CIS major in college and I can't imagine getting a PHD in math lol. I think I would kill my self before I made a living off of that kind of stuff.