CODEWITHSUNDEEP
javaencryption
user3002714
user3002714

Reputation: 17

How to decrypt a known cipher text with brute force attack?

If i have an already known cipher text and the only information that i know is that the plaintext is English language message.I dont know the plaintext,only that is english language message.

The key is 16-bit.

Which is the procedure that i should follow if i want to decrypt it with brute force attack??

Upvotes: -1

Views: 3764

Answers (2)

ROT13
ROT13

Reputation: 375

This strongly depends on the encryption-algorithm. If your message was encrypted with and key of the same length by xoring each letter, you have no chance to decrypt the message. The One-Time-Pad is a perfect secure encryption method (at least if it's used only for one encryption).

In case the message was encrypted with a non-perfect-secure method you should iterate over the key-space (the space all possible keys for encryption live in). Afterwards you have to check whether the resulting decrypted message is plausible to be the original message. For that you could check whether a dictonary contains substring of your candidate.

Again, it's pretty hard to describe a way to decrypt your message without any knowledge of the algorithm which was used for encryption.

Upvotes: 1

Martin Dinov
Martin Dinov

Reputation: 8825

If you want to fully automate the brute forcing, you need to know when the brute forcing/decryption has been successful - that is, you need to keep checking the decryption output and match it against a long dictionary of English words. If there is a strong match for the plaintext with known English words, then you've probably successfully decrypted it and can stop.

Note that even with a 16 bit key, depending on how the encryption was done, this is not entirely trivial to do, as you still need to know something about the encryption method.

Upvotes: 0

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