Homomorphic Encryption and Unlinkable PseudoID in 12 Lines of Python

I’m going to give myself a little challenge. I’ll do some homomorphic encryption and unlinkable pseudo IDs in just 12 lines of Python (not including imports and variable declarations), and which will a citizen’s ID.

We have data sources which can span across the public sector. This might relate to health records, tax records, and so on. The nightmare situation for many is where governments create a data lake, and where all of your data is linked and merged. This would allow your GP to see your tax return, and the tax inspect the chance to see your health record. An improved solution is thus for citizens to own their own identity, and then allow them to link it between disparate systems.

So, let’s say that you don’t trust your government to match your identity across different data systems. Two of the best method proposed for this matching are known as CL-15 and CL-17:

• [CL-15] Camenisch, Lehmann. (Un)linkable Pseudonyms for Governmental Databases. CCS’15. [Link]
• [CL-17] Camenisch , Lehmann. Privacy- preserving User-auditable Pseudonym Systems. IEEE EuroSP’17.