Dr. David Chaum


Spiritual Father of Cypherpunk

Cryptography Legend

Dr. David Chaum is a world renowned cryptographer, famous for the development of eCash, an electronic cash application that aims to preserve a user’s anonymity. He received his Ph.D. in Computer Science, with a minor in Business Administration, from the University of California at Berkeley. He has taught at New York University Graduate School of Business Administration and at the University of California. He built up a cryptography research group at the Center for Mathematics and Computer Science (CWI) in Amsterdam and during this time also founded DigiCash.

At Berkeley, he worked on cryptographic protocols for establishing trust between mutually untrusting parties. Interested in the potential of the Internet from the onset, Chaum began to think about models that would make electronic commerce feasible. What eventually resulted was a new method for making electronic transactions untraceable, Chaum’s blind signature protocol. Applied to an online payment transaction, this new protocol assured a bank or merchant that payments were not forged, while also assuring users that information about them and their purchases could not be traced.

In 1993, he left CWI to become CEO of DigiCash, the producer of eCash, which had doubled in size since its founding in 1990 with 12 employees. In 1999, he left DigiCash to concentrate on secure election voting applications. His newest development is SureVote, a voting receipt that can be printed by a modified version of familiar receipt printers. Under Chaum’s system, a person selects candidates on a touch-screen terminal and presses “finish” when complete. The machine prints out an anonymous receipt on a double-layer of translucent plastic, which displays the names of candidates the voter selected. If the receipt appears accurate, the voter peels the two layers of plastic apart, and in doing so, the text printed on top of the receipt disappears. This keeps the vote secret. Chaum originally developed SureVote for use in emerging countries where elections are often thrown out after their integrity is called into question. After the November 2000 U.S. Presidential Election, he adopted the approach and founded SureVote.

ANON interviews Dr. David Chaum
April 2004

ANON: You wrote the first ground breaking article in the Scientific American on anonymous cash. Can you tell us what you think has happened since that article was published? Do people understand and appreciate the need to protect their identities?

DAVID CHAUM: I think the appreciation of personal privacy and information in context of technology has been growing steadily since the 80’s. A number of people became so worried about it, such that their concerns were saturated and they gave up worrying about it. The article was not just on e-cash, but anonymity and comprehensive privacy solutions.

ANON: Can you explain what you mean by the term “secure election voting”?

DAVID CHAUM: there are four issues involved in secure election voting. The integrity of how votes are counted along with transparency in the counting process is most important. Ballot secrecy allows voting where an individual can vote without being influenced by an other and without being able to convince others of how they voted. The robustness and survivability of the system is also necessary to ensure that it can withstand disruption. Finally, election voting should provides access to the widest range of voters.

It has been tricky for secure e-voting to achieve integrity and secrecy at the same time. Until this work, there hasn’t been a good solution.

ANON: What does secure voting have in common with electronic cash?

DAVID CHAUM: Both are applications of cryptography. These systems are both different from many typical automation systems in that they empower the individual to interact with society in a way that is secured by the individual. They differ substantially in the way that they handle two fundamental properties of information systems: secrecy and authentication. In e-cash, privacy is unconditional and doesn’t depend on the bad guys being unable to break codes. With e-voting, it is the integrity of the system that cannot be compromised; privacy can be violated if the adversary has enough computing power.

ANON: The secure voting systems you write about emphasize receipts. Does that go hand in hand with non-identification?

DAVID CHAUM: Receipts don’t contain the identity of the voter but contain a random identifying number so you can look up your vote on the Web. The voter can check their vote accurately and reflect on their ballot. With provisional voting – when voter is told that the name is not listed on the roster, they can submit the vote, but it may or may not be counted depending on the checking that takes place afterwards – so in that case the voter’s name is associated with the encrypted vote that is printed on the receipt. In both cases, there is privacy for the voter and the vote is anonymous.

ANON: What could online voting do for democracy?

DAVID CHAUM: It could enfranchise a larger class of people who can’t attend polling stations. More fundamentally, it reduces the cost and time needed to have an election and could involve more participation by individuals and allow for elections to be held on a more impromptu or as needed basis. There are other differences that haven’t received a lot of attention. For example, the voter in an online setting may have access to all kinds of information such as the voting behaviour of candidates and recommendations of other groups and individuals, etc. So the voter can make a more informed and complex vote.

ANON: In your view, what is the connection between democracy and the preservation of anonymous means of interacting?

DAVID CHAUM: Freedom of expression and participation without fear of retribution is the basis for democracy. Anonymity is the only known means to achieve it – that’s why anonymity is essential in voting.

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