Background: I've been thinking about using encryption in the context of backing up files to untrusted locations (to the point of making the file publicly and widely distributed for practically failsafe backup).
The problem is, once a file is publicly available, it will forever remain so. And in 20 years, when computing power is unpredictably faster, AES256 bit encryption might be practically useless - and my private backup file readable to all.
I was thinking, as a deterrent to brute force attacks on encryption, what if when the wrong password was tried the algorithm returned dummy data that would require human examination to assert that the data is not what the attacker is looking for.
I encrypt the plain text (say, an account number) '123456789' with the password 'pass'.
Attacker attempts to brute force the encryption and tries the password 'a'.
The result is '987654321'.
Now, how is the attacker to know that this is not the value I encrypted, and that the password I used was 'a'? Additionally, even if the attacker guesses the password 'pass', how are they to know that '123456789' is the correct value?
This of course is a simple example and most people encrypt somewhat recognizable artifacts; human language text, files recognizable by headers, etc. So this idea could be expanded to not just scramble data upon output, but also to include a variety of generated 'dummy' artifacts (common file formats, samples of language text, etc) not necessarily included in the core algorithm (the dummy data could be user defined). The dummy data output on incorrect passwords could then possibly include valid JPEG files, WORD files, PNG files, and samples of valid text from a variety of languages.
The result would make the encrypted file very hard to brute force without either a huge amount of computing and human power, or specific knowledge of what is encrypted.
Are there any algorithms out there that work like this? Are there any flaws in the idea itself?