0
$\begingroup$

Given a block of data, say

THE+ QU+ICK+ BR+OWN+ FO+X J+UMP+ED +OVE+R T+HE +LAZ+Y D+OG

Is there any method of encryption that will make the knowledge that the '+' character will always repeat every 4th character useless for cracking the key used to encrypt the data?

If there is, how does that encryption work, and why would a known signal not enable you to break the code?

Please assume that the use of '+' as a repeating signal is merely an example, and that the signal can be as large and complex (or small and simple) as needed to prevent an encryption system from making that signal useless.

What I'm ultimately trying to figure out here is "Can I arrange my data in such a way that it is impossible for a malicious actor to hold it for ransom using any modern or theoretical encryption system."

This means that I don't actually care about the key, and I can know from the beginning that I'm looking at ciphertext, not randomly generated data meant to obfuscate my decryption attempts.

It also means that I'm assuming my goal isn't to elegantly decode the data by guessing the key in one try, instead I simply want to transform a brute force key cracking attempt requiring 1,000,000+ years into an attempt that will require a few days at most.

Improve this question
$\endgroup$
2
  • 1
    $\begingroup$ The title of the question asks a totally different thing than the body. Title wants to mitigate modern encryption, that is decipher without knowledge of the key; body wants to mitigate a known characteristic of the plaintext, that is make it impossible to decipher without knowledge of the key. $\endgroup$
    – fgrieu ♦
    Aug 24, 2021 at 6:09
  • $\begingroup$ The question in the body is intended to ask for a specific example that would make the question in the title impossible. $\endgroup$
    – Catachan
    Aug 24, 2021 at 13:05

1 Answer 1

Reset to default
3
$\begingroup$

Is there any method of encryption that will make the knowledge that the '+' character will always repeat every 4th character useless for cracking the key used to encrypt the data?

Actually, any encryption method that is considered secure nowadays would do that.

In fact, the goals we place on encryption is even more strict; we even consider the cases where the attacker can specify the plaintext, and will still insist that he cannot distinguish the ciphertext from random data of the same length.

Improve this answer
$\endgroup$
8
  • $\begingroup$ Of course, but there's a useful counter example; Enigma. $\endgroup$
    – Paul Uszak
    Aug 23, 2021 at 22:46
  • $\begingroup$ @PaulUszak: I assume you mean an example of a cipher that is not considered strong nowadays, and exhibits such a weakness... $\endgroup$
    – poncho
    Aug 24, 2021 at 2:32
  • $\begingroup$ Assuming the the attacker doesn't have to distinguish the ciphertext from a random string of data, and that the attacker doesn't need to be able to extract the key, merely reverse the encryption, does that change anything? $\endgroup$
    – Catachan
    Aug 24, 2021 at 13:10
  • $\begingroup$ I'm going to edit the question to add a little bit of clarification of why I'm asking this in the first place. This is a really good answer though so far! Thank you. $\endgroup$
    – Catachan
    Aug 24, 2021 at 13:11
  • $\begingroup$ @Catachan: no; we use the model 'distinguish the ciphertext from a random string' because we can show that if he can get any information about the ciphertext at all, then he can use that to distinguish; hence if he can't distinguish, then he can't get any information at all $\endgroup$
    – poncho
    Aug 24, 2021 at 13:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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