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Understanding Cryptography

PostPosted: Mon Apr 28, 2008 12:39 am
by ELorenz
I was just curious about how many people feel they have a truly good understanding of modern cryptography here.

I also figured I'd try to get things going in this area of the forums.

Do people here know about the different algorithms out there? RSA, MD5, etc. What they are and what they do?
I'm also curious about the laws regarding this thread if anyone knows them, I know the laws regarding crypto are pretty screwy at least in the US, especially since the Digital Millenium Copyright Act.

Personally, I understand the ideas, and I've learned a little about the attacks and processes, but just enough to start a discussion.

Re: Understanding Cryptography

PostPosted: Mon Apr 28, 2008 10:24 am
by Fors4ken
Cryptography is an interest of mine but Im quite the novice. I am familiar with several algorithms in use today but have only begun attempting to truly understand their operations and be able to do one on paper. Right now I am reading about the history of cryptography.

Re: Understanding Cryptography

PostPosted: Mon Apr 28, 2008 1:34 pm
by jamey

Re: Understanding Cryptography

PostPosted: Wed Apr 30, 2008 4:01 pm
by yourmysin
Cryptography is actually a hard topic to learn about. Sure, you can learn the basics very easy, but once you begin putting together your own algorithms you realize how tough it is.

Start by brushing up on your mathematics, then read some books about it. Anything by Bruce Schiner is great.

Re: Understanding Cryptography

PostPosted: Wed Apr 30, 2008 6:14 pm
by TheMindRapist
Wtf @ jamey, lose the caps.
And if you actually want to learn it then research don't ask to be spoon fed info.

Re: Understanding Cryptography

PostPosted: Wed Apr 30, 2008 10:42 pm
by ELorenz
I agree that the all caps are a bit excessive, and just saying help me isn't a good way to get people interested in discussing things. A good place to start on the mathematics side is linear algebra, learn what linear transformations are, and how to manipulate matrices.

Re: Understanding Cryptography

PostPosted: Mon May 19, 2008 6:37 pm
by JC5
for this. basically the only cryptography u need to look up is the ?

then the way it works is

ex. 2564pm98

the way it woould work is

then next number is -1
then -2 all the way to 4
so the new numbers for htem would be

2441 NOW u need the alphabet ones this is the same principle
we are currently at -4
so in the alphabet p - 4 is (abcdefghijklmnopqrstuvwxyz)
^m is the answer. now do the same with p (p-5) and u would get k

so its 2441mk now 9-6 is 3 and 8-7 is 1
so from 2564pm98 our new encrypted example is 2441mk31

does that clear the questions up?

Re: Understanding Cryptography

PostPosted: Tue May 27, 2008 6:05 pm
by ELorenz
I'm assuming that you are talking about the basic mission that involves cryptography in a very basic form. I was actually trying to start this post as a way to discuss real algorithms and their construction, maybe even a little of the weakness of each if people know them.

Do people here know what a symmetric and asymmetric algorithms are? if not and you're interested that would be a good place to start with.

Re: Understanding Cryptography

PostPosted: Thu May 29, 2008 2:05 pm
by JC5
I am actually a very nice mathmetician. Math is easy and spotting paterns even easier. the logic mission i completed in like 5 minutes lol. if u need help with it pm me btw. im in junior year. now a senior that they graduated and im takin ap calc 2 next year :D

Re: Understanding Cryptography

PostPosted: Thu May 29, 2008 8:26 pm
by int3grate
I have a fairly good understanding of cryptography.

As far as math goes, most modern cryptography requires a good understanding of some number theory (modular arithmetic, prime numbers, and finite field arithmetic), as well as a good understanding of Linear Algebra, some calculus, and boolean algebra.

It's really not that hard to figure out how algorithms work and how to code them, the trouble comes when analyzing them to determine the amount of secrecy they provide, and performing cryptanalysis. The best way to start learning Cryptography (IMHO) is to start with the classical ciphers such as Caesar, vigenere, Hill, etc..., and work your way up from there to the modern ciphers.

A really nice learning tool that I've used to explain cryptographic algorithms is Cryptool ( It allows you to cipher and decipher text on almost every cipher known to man, has some attack and analysis tools, and has some really nice interactive things built into it that show you how the cryptographic algorithms work. I highly recommend you download it (unfortunately it doesn't work in Linux very well...).

There are several good books on Cryptography. A lot of people mention Bruce Schneier books on Cryptography, but I think they lack the mathematical detail that is needed to really understand how a cipher works, and what the weaknesses are. His Applied Cryptography book doesn't even cover AES (or the rijndael cipher), and that's what everyone uses nowadays.

I would recommend finding a college level book on Cryptography if you really want to understand it.

Also there is a lot of documentation on the web. There are several FIPS (Federal Information Processing Standard) publications covering different areas of cryptography that are all good reads, and there are Wikipedia articles on just about every encryption algorithm known to man.

I hope this information helps. Good luck on your adventures into the world of Cryptography.