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avatar Crypto

Is it Possible to Prevent/Mitigate Modern Encryption of Data by Using A Known Signal?

id flag
Catachan

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.

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fgrieu avatar
ng flag
fgrieu
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.
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id flag
Catachan
The question in the body is intended to ask for a specific example that would make the question in the title impossible.
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Score:3
poncho avatar Crypto
my flag
poncho

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.

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Paul Uszak avatar
cn flag
Paul Uszak
Of course, but there's a useful counter example; Enigma.
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poncho avatar
my flag
poncho
@PaulUszak: I assume you mean an example of a cipher that is not considered strong nowadays, and exhibits such a weakness...
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id flag
Catachan
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?
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id flag
Catachan
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.
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poncho avatar
my flag
poncho
@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
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id flag
Catachan
@poncho, thanks that makes sense, so what you're saying is that it's not a matter of signal to noise ratio in the data, it's actually a matter of maximizing information entropy when it comes to modern encryption?
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poncho avatar
my flag
poncho
@Catachan: I wouldn't use the term 'information entropy', as that would imply that we're informationally secure, and we're not. Instead, it is having sufficient computational complexity...
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id flag
Catachan
Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/128896/discussion-between-catachan-and-poncho).
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