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Anamorphic encryption against dictators - hiding message inside normal looking ciphertext (eprint.iacr.org)

submitted 8 months ago by hematite@programming.dev to c/privacy@lemmy.ml

21 comments fedilink hide all child comments

I want to share an interesting cryptography paper which introduces "anamorphic encryption", where the ciphertext encrypts two messages. One is a message to reveal to a dictator, who wants the secret key and message to control the narrative. Behind it lies a hidden message, guarded behind a "double key", which is to communicate messages of intent secretly.

It's kind of like having a duress key to reveal, but instead you can send real messages with the real key.

For instance, an investigative journalist could encrypt a fake message "Everyone is content in our utopia" as a smokescreen to show to the dictator, while true messages like "Minorities are forced into labor camps" can be hidden in the anamorphically encrypted ciphertexts to notify the outside free press.

The authors argue that cryptosystems already in use supports the anamorphic mode, where you encrypt a normal-looking ciphertext which contains the hidden message.

Given that it has been 3 years since this paper, I think there would have been some applications of this technology. Do you guys know of any?

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[–] icelimit@lemmy.ml 1 points 8 months ago (2 children)

Isn't there some information theory that says you can't have two pieces of unique information inside one ?

[–] ReversalHatchery@beehaw.org 3 points 7 months ago (1 children)

the way it works is that the veracrypt container basically contains 2 encrypted partitions. if it can't decrypt the first one with the password, it will try the second one, but always pretend to try both so that the time it takes to unlock it does not give it away. by writing to either, you risk overwriting data in the other one (except that you can input both the hidden and main partition passwords and it will make sure to keep the hidden partition unaffected), but otherwise both partitions are fully functional

[–] icelimit@lemmy.ml 1 points 7 months ago* (last edited 7 months ago) (1 children)

But if two different messages are encrypted with the same key, doesn't it by nature produce two different ~~'plaintext'~~ ciphertext? Unless the real secret is much smaller than the decoy message as in the example of the ww2 artist

[–] ReversalHatchery@beehaw.org 1 points 7 months ago (1 children)

plaintext is the unencrypted form of data. encryption produces ciphertext. encrypting the same data with the same key twice results in the same ciphertext, unless additional steps were taken to insert additional data that does not match (like a nonce) to the plaintext

[–] icelimit@lemmy.ml 1 points 7 months ago

Sorry. Got the terms mixed up. Ciphertext is it. Thanks

[–] phoenixz@lemmy.ca 1 points 7 months ago (1 children)

Not sure about that, but this is basically a few clever tricks where you have two file systems in one volume. Obviously if the volume is, say, 10 gigs, you can only store 10 gigs in total on those filesystems, as they share the space.

You also, likely, wouldn't want to fill up the drive too much

I don't know what happened to it, I recall that, years ago, they found various weaknesses in the system but instead of fixing it, it seemed to be abandoned. I'll start looking around if he there are updated open source versions

[–] icelimit@lemmy.ml 1 points 7 months ago* (last edited 7 months ago) (1 children)

Wouldn't it then be a simple matter to notice that a 10gb for only yielded 5gb of "innocent" data after decryption?

Especially since it would be (I assume) simple to 'predict' the size of the ("unnested") plaintext if the cipher and key is known

[–] phoenixz@lemmy.ca 1 points 7 months ago

Found it: https://www.truecrypt.org/

All the questions you have can be answered there. I haven't used it for over 5 years, so honestly I don't recall what it can ans can't do, but I do remember that you could have a hidden volume somewhere