Reply to post: Re: The key is not stored

Re: The key is not stored

boltar wrote:

"Except in your example the relationship of the original numbers is maintained when converted to logarithms."

Yes the ordering relationship is maintained, and there is a mapping of the multiplication operation in cleartext to the ciphertext - addition. In 'industrial strength' systems the preserved properties and mapping of operations are not so trivial - that is why the analyses are so much slower.

"However no relationship will be maintained between any properly encrypted data ..."

There is always a relationship between ciphertext and cleartext - otherwise you could not decrypt it. In homomorphic encryption some further relationships are possible (without knowing the cleartext).

"... (and not only that, if the input has been shuffled first you won't even know where the data is) ..."

So don't shuffle it - there are other ways of hiding live data, e.g. amongst sets of random data.

"... unless the encryption method specificially allows it."

Exactly! And guess what is special about homomorphic encryption.

"And a decent one won't."

Disagree - but then I am taking on trust the rigour of the maths behind homomorphic encryption (just as I take it on trust that the rigour of other methods of encryption). Your suggestion that it is not 'a decent encryption' does not shake my belief.

Bear in mind that homomorphic encryption has different objectives than many other forms of encryption - so it makes different tradeoffs.

"So either there are known holes in numerous ciphers or there's something they're not telling us."

Well there are known holes in numerous ciphers, the literature abounds with them - but not practically exploitable holes in decent ones; and I am sure there is plenty that they (who?) are not telling us. But neither of these points seem relevant - or are you aware of a practically exploitable hole in homomorphic encryption that they are not telling us about. What makes you believe this?