How to identify encryption algorithm used in ciphertext?

Question

Is there any ways to try to guess encryption algorithm used to encrypt the ciphertext?

Answer 1

Quite often this information is readily available - in a good encryption scheme, only the key needs to be secret, not the algorithm used.

There are analyses you can can perform to test for particular encryptions, consult a textbook on cryptanalysis for details!

Answer 2

Yes. There are some differences:

• Is it a block cipher or not can be guessed from the length.
• Block length
• Entropy of the output (are all characters equally present? / can patterns be found?)
• Recurrences (CBC or not...)

The entropy of the string is probably the best hint. A simple method to determine it is probably trying to compress it. Some methods can be found here: http://www.random.org/statistics/ They use them to make sure their numbers are as random as possible.

I've got no idea if it's really possible to determine the encryption using these methods.

Answer 3

Tools to see it:

• PEiD with the Krypto Analyzer (KANAL) plugin
• IDA Pro with the Findcrypt plugin
• OllyDbg with the SnD Crypto Scanner
• x3chun's Crypto Searcher
• Keygener Assistant
• Hash & Crypto Detector (HCD)
• Draft Crypto Analyzer (DRACA)

but all to executables. found here : http://fwhacking.blogspot.com.br/2011/03/bfcrypt-crypto-scanner.html