A simpler implementation would be a decryption program that with a secondary password simply returned gibberish from the encrypted data with the error “Unrecoverable error: Encryption failed, restore from backup.”
I could be wrong (this is just a gut feel), but it seems that the resulting file doesn’t necessarily have to be larger but the trade-off is compute time to determine the two transformations with minimal keys that arrive at the desired outcomes.
This is the Zodiac speaking,
Maybe I’m not reading this correctly, but isn’t this what PGP essentially did? It made each user have a public key and a private key, so the public key could be compromised without losing the encrypted data.
Or are we talking about a way to encrypt data that, if the key is compromised and the data is decrypted, it will in actuality still be hiding the REAL secret message?
Sorry if I’ve confused the issue more. I am not sure I’ve understood the OPs requirements.
What if you used some kind of palimpsest encryption?
Take a file of apparently random noise, a simple image, a musical sample, etc, and apply a password to get a message hidden in the data.
Apply another password to THAT and get an even more deeply buried message…ad infinitum.
Not really. Here’s a very simple steganography method for Jpeg that will reduce an image’s size (slightly) and actually improve the image’s SNR!
The count of odd coefficients in a Jpeg block will be either even or odd. Concatenate those count parity bits to form the secret message. This might mean the secret is less than 1% the size of the Jpeg file (say, 1 bit per 64 pixels), a problem with all steganography techniques.
Starting from the unaltered Jpeg (and having its higher-precision form available for the algorithm), half the blocks will need their odd/even sense flipped to yield the desired secret message. Flip, when needed, whichever coefficient is closest to threshold, so its change will have minimal effect on image quality. In many cases the best flip will be to change a +1 or -1 to zero – a change which will actually improve SNR, though only the best (non-steganographic!) Jpeg compressors take advantage of the idea.
I never said that the interrogator destroyed their only copy - they may have destroyed the suspects only copy.
People tend to equate hidden with safe - in the case of a hidden partition, this is not true. It is also not true of a bunch of other things, like money in a mattress, but people do it all the time.
People also do not maintain backups, and are less likely to do so when it takes considerable work, like maintaining encrypted copies. The corollary is also true, multiple copies of encrypted data make it more likely that the data is important.
Some people get emotionally invested in their data. Particularly if the data in question is personal and specific and not able to be recovered or represents a great deal of effort. I have heard that in the case of something like child pornography, this attachment to the material can be extremely strong, and can override self-preservation.
Encryption is intended to raise the cost of accessing data without the specific key - no encryption is immune from a brute-force attack, but the cost/time of that attack is expected to be higher than the value of the encrypted data. But knowing that there is possible data to be found is often as important as the data itself. And sometimes people reveal more than they intend.
Si
Yes, but only for some cases - in others, the result of the computation will be that no minimal key is possible. If it were otherwise, we’d be able to encode any amount of data into a finite space.
That’s exactly what the OP is asking, but it’s not possible.