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# The Witness Algorithm: Privacy Protection in a Fully Transparent System
By **Vlad Gluhovsky** and **Gavin Wood**

# Introduction

Being based upon a quasi-Turing-complete (quasi because it's actually bounded) virtual machine, Ethereum is an extremely versatile system. However one of its greatest strengths---universal auditability---seems to lead to a fatal flaw, namely an inescapable lack of privacy. Here we demonstrate an algorithm in order to prove that this is not the case.

The algorithm could be used to make an Ethereum contract which, given two sets of addresses sources, `src`, and destinations, `dest`, will guarantee exactly one of two possible eventualities:

- For each address in `src`, the controller of that address controls a corresponding address in `dest` (though the two cannot be related *a priori*).

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