Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

I am in attempt to understand relative insecurity of certain encryption schemes. Particularly of interest is DES and RC2. I know AES is better and should be used to encrypt. But practically, if something is encrypted with (1) DES or (2) RC2 (3) RC4 what level security is achieved.

In affect I am asking:

If a adversery is given a {DES/RC2/RC4} ciphertext, is it possible that they can decrypt or can a determined adversary definitely decrypt?

share|improve this question
    
For DES the answer is that it can definitely be decrypted using brute-force. A 56 bit key is far too small. –  CodesInChaos Jun 3 '13 at 5:09
1  
It depends on the type of attack which is possible. If your plaintext is random data without any structure, every encryption scheme (with a key size of more than zero) is "secure" against "definitely retrieving the plaintext". –  Paŭlo Ebermann Jun 3 '13 at 7:25
add comment

1 Answer

Yes, an adversary can definitely decrypt a DES message, given sufficient funding. Fifteen years ago, in 1998, the EFF built a DES cracker (nicknamed Deep Crack) that can recover a DES key in a day. Today, anyone with the money can purchase a commercially available DES cracker named COPACOBANA.

For RC2, I'm not aware of any practical attacks. (You still shouldn't use it.)

For RC4, the answer is complicated. It depends. It depends upon how you use RC4. There are lots of attacks known, and whether they will be applicable or not to your particular situation will depend upon many fine details of your particular situation.

share|improve this answer
    
Thanks for the great edits, @JohnDeters! –  D.W. Jun 3 '13 at 19:03
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.