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Hey guys - I need some regarding ciphers! First of all - how do you generate a cipher?

You don't generate a cipher, a cipher generates you.

http://en.wikipedia.org/wiki/Cipher

dtpqwnkts

Phew. This is gonna take a long time to grasp...

Rajiv wrote:Phew. This is gonna take a long time to grasp...

What exactly do you need a cipher for?

Its an IT project. We need to do research and stuff - then we need to code a program in Java that can encrypt and decrypt a file...

you're writing your own security provider classes or is this simply an attempt to introduce you to the security API?

• 1) Pick a cipher: Asyncrhonous/Synchronous
  2) Use the security API to create the necessary digests/keys

You may want to spend some time understanding what Base64 conversion is and why it is a necessary component when dealing with encrypted IO...

Rajiv wrote:Its an IT project. We need to do research and stuff - then we need to code a program in Java that can encrypt and decrypt a file...

How big are the files? Can you load it into a byte array and shift it?

Bladerunner wrote:

Rajiv wrote:Its an IT project. We need to do research and stuff - then we need to code a program in Java that can encrypt and decrypt a file...

How big are the files? Can you load it into a byte array and shift it?

Exactly what you will be doing. The encryption APIs of Java work from Streams. It could be a buffered byte array or not it does not matter.

RuadRauFlessa wrote:

Bladerunner wrote:

Rajiv wrote:Its an IT project. We need to do research and stuff - then we need to code a program in Java that can encrypt and decrypt a file...

How big are the files? Can you load it into a byte array and shift it?

Exactly what you will be doing. The encryption APIs of Java work from Streams. It could be a buffered byte array or not it does not matter.

Yes but if it's a big file you'd rather take a bunch of bytes at a time, encrypt them, and write them to a new file. When you're done with all the segments you close the filestream.

If it's small, like a text file or word doc, you could probably load the whole file into a byte array.

It would be a small file based on my problem statement.
The rubric for the project says I need to state the inputs, processing and the outputs. The input would be the file that needs to be encrypted/decrypted, right?
How do I structure the 'processing' part and the 'output' part?

there are millions of examples out there...

the trick is understanding what best practices are and why they're considered best practices... (just be thankful you weren't asked to deploy a CA and fiddle with SSL)..

you may also want to consider playing with something like bouncycastle - purely because the legal wrangling in yank-land sees java shipped with a severely limited provider implementation...

have you ever dabbled in cryptography or is this your first visit? - because there's a lot of groundwork you need to cover...

first visit...

symmetric

• :-fast and far more secure
  :-security relies on trust between parties, (shared password/key)
  :-typically used on large amounts of data
  :-susceptible to volume attacks

asymmetric

• :-slow
  :-security is adaptive and can be negotiated on the fly using disposable key-pairs..
  :-typically used on small data sets
  :-susceptible to digest and volume attacks...

in the real world you will generally encounter a blend of the 2... an asymmetric session would be used to exchange some form of salting data in order for both parties to create a disposable symmetric cipher for that session...

because the salt is random it has the appearance of noise so even if the asymmetric cipher is compromised there's a relatively low risk of having the symmetric cipher compromised as well...

by the sound of things, your project would be best suited to the symmetric cipher approach? - asymmetric would require that you store/share the private/public keys...

OK thanks. Any more info?

Jav Cryptography Extension - Reference Guide - simple encryption... (although i would advise using AES over DES...)

i wasn't kidding.. this example is reproduced everywhere...

Thank you!!!!! That info is what I need for the 3rd step of my project!!!!!