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The Homomorphic Encryption Patent Land Rush

I noticed this morning that Google patent search returns 189 results for the query “homomorphic encryption." I have written about homomorphic encryption in the past; it is a true mathematical breakthrough which has the potential to transform cloud computing security. But the emphasis, here, is on “potential.” There is no fully homomorphic encryption scheme which is efficient enough to be practical for real-world, general-purpose computation.

This, apparently, has done nothing to stop the patent land rush for any process which might conceivably utilize homomorphic encryption. Some of these are legitimate under the current rules of U.S. patents, even if you personally find those rules wrongheaded. For example, IBM has filed patent claims on Craig Gentry’s breakthrough algorithms.

On the other hand, it is not difficult to find patents which don’t so much describe an invention as speculation on what someone might invent in the future. It reminds me of the well-worn economics joke, "Assume a can opener…" Some of these contain amusing disclaimers, such as the following:

Currently there is no practical fully homomorphic cryptosystem, that is, there is no secure cryptosystem that allows for the homomorphic computation of additions and products without restrictions. There has been a recent contribution by Gentry that presents a cryptosystem based on ideal lattices with bootstrappable decryption, and it is been shown that it achieves a full homomorphism. Nevertheless, the authors of this method to concede that making this scheme practical remains an open problem.

Others invoke a form of rhetorical hand waving more commonly seen in freshman term papers than patent applications:

There exist well known solutions for secure computation of any function e.g. as described in [45]… The general method employed by most of these solutions is to construct a combinatorial circuit that computes the required function… It seems hard to apply these methods to complete continuous functions or represent Real numbers, since the methods inherently work over finite fields.

The “well-known” solutions, here, are both computationally impractical and covered by other patent applications. And “seems hard” is really not the right phrase to pick when you are describing a problem for which there is no known solution.

In 2004, Phillips filed a patent application for the very idea of homomorphic encryption. Never mind that no algorithm for fully homomorphic encryption existed at the time, and that Phillips did not invent the idea itself. Buried in paragraph 69 are the following weasel words:

An encryption scheme with these two properties is called a homomorphic encryption scheme. The Paillier system is one homomorphic encryption scheme, but more ones [sic] exist.

Note that Pascal Paillier does not appear to work for Phillips, published his encryption scheme 5 years prior to this patent application, and Paillier encryption is only homomorphic with respect to addition.

Some approved patents venture into the absurd. Remember the string concatenation example I used in my first article on homework encryption? Folks who follow my public speaking closely (hi, mom!) will remember that I sometimes joke about a startup selling cloud-based, homomorphically encrypted string concatenation ("Concatenatr"). It’s a joke, right? You can stop laughing now; SAP actually received a patent for that one.

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