Homomorphic Encryption Library Released

May 2, 2013

One of the issues that tends to come up when people consider the possible use of “cloud computing” is data security.  The data can be stored in an encrypted form, of course, but it generally has to be decrypted in order to be used; this means that the data is potentially vulnerable while it is is plain text (decrypted) form.

I’ve written before about the potential of homomorphic encryption to address this problem.  The basic idea is that we would like to discover an encryption function such that a defined set of operations can be performed on encrypted data (say, adding them) to produce an encrypted result that, when decrypted, is the same as that obtained by operating on the plain text data.

In other words, if we have two numbers, α and β, and suitable encryption and decryption functions E(x) and D(x), respectively, and if

α + β = S

Then, if

E(α) + E(β) = S*

it will be true that

D(S*) = S

So we are able to add the two encrypted values to get a sum that, when decrypted, is the sum of the original (unencrypted) numbers.

This sounds almost like magic, but it has been proved to be theoretically possible, and there is a considerable amount of ongoing work to try to reach a practical implementation.  (For example, back in 2011, a group of researchers at MIT introduced CryptDB, database software that incorporates homomorphic encryption in a form suitable for some applications.

Now, according to an article at the I Programmer site, researchers from IBM’s Thomas J. Watson Research Laboratory have released an open-source library for homomorphic encryption, HElib (documentation and source code available at Github).

HElib is a software library that implements homomorphic encryption (HE). Currently available is an implementation of the Brakerski-Gentry-Vaikuntanathan (BGV) scheme, along with many optimizations to make homomorphic evaluation runs faster, focusing mostly on effective use of the Smart-Vercauteren ciphertext packing techniques and the Gentry-Halevi-Smart optimizations.

Although, as Bruce Schneier has observed, it will take a fair while for any of this technology to be scrutinized thoroughly enough by enough knowledgeable people to ensure that it doesn’t have serious flaws, getting algorithms and code out and available for inspection is an essential part of that process.

Update Thursday, May 2, 22:59 EDT

I have changed the headline/title of this post; originally, it was “IBM Releases Homomorphic Encryption Library”; that could be interpreted as describing an “official”  corporate action of IBM.  Since I have no knowledge, one way or another, about this sort of thing, I thought the new headline was less likely to lead to misunderstanding.

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