encryption types

jamesleecoleman

I know that it is possible to look at some cyphertext and know what kind of encryption was used.
Does anyone know of a good website or book that has examples of the different examples of cyphertext???
I've tried googling for help but I didn't get anywhere helpful.

I'm trying to figure out what encryption was used on this cyphertext and I feel kinda stupid trying to figure it out.

JDMurray

Good encryption algorithms produce cipher-text that has a very high degree of entropy and disorder of the information. If you can tell the encryption algorithm used to create a piece of cipher-text based only on the information in the cipher-text, you are dealing with a very poor encryption algorithm.

dmoore44

OP - are you referring to the PGP declaration at the beginning of PGP signed e-mails? That's the only instance I can think of in which an encryption scheme declares itself...

jamesleecoleman

dmoore44: No, I didn't see anything that had to do with PGP. JDMurray explained it pretty well to me.

Thanks everyone for letting me know though.

paul78

@jamesleecoleman - Someone else mentioned this a few weeks ago - but if you missed it - check out Coursera. There's a pretty neat course on Crypto - that's free. https://www.coursera.org/course/crypto

jamesleecoleman

Thanks Paul!! I hope this helps me with my Cryptography class that I have to take.

dmoore44

@paul78 - thanks for the heads up! Based on the link you provided, I enrolled in that crypto course.

jamesleecoleman

The reason I made this post was because I'm working on a challenge and I can't ask questions about it. I'm not asking for someone to do this for me. It's just that I don't go this far into encryption. I've dealt with the rotational and the base64.
I'm told that the code is one continuous block. So I figure that it is a block cipher (started to look at what uses block cipher). Does anyone have any advice on what type of questions I should be asking in order to better understand how I should be doing this? Or is this one of those things where I have to try different methods on decrypting the cyphertext?

JDMurray

The first thing you need to know is the difference between "encoding" and "encryption." Encoding is simply transforming information from one data format to another, as in ANSI-to-Base64. Encryption can be considered a type of encoding specifically designed to prevent the data from being correctly interpreted without special information (i.e., the encryption key). Encoding is performed for convenience and usability, while encryption exists to provide confidentiality and integrity. And both encoding and encryption provide availability.

The next thing to look up is the difference between a block cipher and a stream cipher, and to discover why a block cipher is not for operating on continuous input streams of data. The Wikipedia is your friend here.