I have a file that has been encrypted using DES and am looking to decrypt and find a secret message encoded. All I have is the file which is full of binary data. There is no key or anything else which makes me wonder how can I be able to do it by Brute Force.

I spent some time reading and understanding DES and I know how it works but would appreciate some advice.

  • $\begingroup$ Requests for analyzing or decyphering a block of data are off-topic here, as the results are rarely useful to anyone else. $\endgroup$
    – e-sushi
    Nov 9, 2013 at 22:17
  • 3
    $\begingroup$ Short answer: brute force is feasible thanks to the small key-space $\endgroup$ Nov 9, 2013 at 23:03

1 Answer 1


Brute force is feasible as codesinchaos points out. That said there is more to it than that.

First you'll need some way to tell whether or not decryption was successful. For example, you may look for english language text upon decryption. Automating this will be essential as you don't want to manually look at every decryption to decide whether or not you were successful.

Second, you'll have to try different modes. If it was encrypted with ECB, you should be able to recognize that by looking at the ciphertext (see if there are lots of repeated blocks of ciphertext; a block in des is 8 bytes). Otherwise, you'll have to try all the common modes. Still, should be able to be accomplished via brute force.


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