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I have problem called CTB-Locker. It encrypted all of my files on computer and since I have lot of documents that are very important I am in problems!

As I read online CTB-Locker uses "elliptical curve cryptography" but I have no idea what that is!

But there is 1 bright spot about this! I have 1 original zip file that is encrypted and I have that same file without encryption (original). Can I maybe get decryption key from that file? It's size is around 100 MB.

Can you help me please this is very important for me :( I am currently using Ubuntu & Windows 7 so if there is any programs that can do that please tell me.

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closed as off-topic by e-sushi, Seth, Reid, mikeazo Apr 7 '15 at 20:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Requests for analyzing or deciphering a block of data are off-topic here, as the results are rarely useful to anyone else." – e-sushi, Seth, Reid, mikeazo
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ If they did a good job, there's no way to crack that. You can search for known flaws with their encryption routine, but without that you're out of luck. (Knowing some pairs of original files and encrypted files doesn't help you with proper encryption algorithms.) $\endgroup$ – Nova Jan 26 '15 at 14:11
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Unfortunately, unless the developers made rookie mistakes in their implementation of their malware, you will not be able to recover the decryption keys. The ideal solution is to recover your files from a recent backup. I suppose you can pay whatever ransom is asked for, if you can morally justify it (ransomware typically has an incentive to give you access to your files again if you do, obviously, but this is no guarantee and be aware you would be playing into their hands). If you have no backups, let this be a lesson in data security and disaster recovery. Harsh, but there legitimately is nothing that can be done, strong cryptography can be used for bad just as it can be used for good, like everything else.

Also don't forget to actually remove the malware and ensure it doesn't end up on your computer again.

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  • $\begingroup$ I'd add that modern cryptography is specifically designed to prevent someone with plaintext-ciphertext pairs from using them to decrypt other ciphertexts. $\endgroup$ – cpast Jan 27 '15 at 1:51
  • $\begingroup$ Thanks for your answer! I can not pay because it is agains law in my country (Croatia). Anyway you saved my time and I am very thankful $\endgroup$ – Ivan32x Jan 27 '15 at 11:00

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