David Chaum

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David Chaum
Born1955 (age 62–63)
ResidenceSherman Oaks, Los Angeles, California, United States
Alma materUniversity of California Berkeley
Known forDigiCash, ecash, IACR, mixes, voting systems
Scientific career
Doctoral advisorBernard Marcel Mont-Reynaud

David Lee Chaum (born 1955) is an American computer scientist and cryptographer. He is famous for developing ecash, an electronic cash application that aims to preserve a user’s anonymity. He has also invented many cryptographic protocols and founded DigiCash, an electronic money corporation.[1]:65–70 His 1981 paper, "Untraceable Electronic Mail, Return Addresses, and Digital Pseudonyms", laid the groundwork for the field of anonymous communications research.[2]

Life and career[edit]

Chaum gained a doctorate in computer science and business administration from the University of California, Berkeley in 1982.[3][4] Also that year, he founded the International Association for Cryptologic Research (IACR), which currently organizes academic conferences in cryptography research.[5]:47 Subsequently, he taught at the New York University Graduate School of Business Administration and at the University of California, Santa Barbara (UCSB). He also formed a cryptography research group at the National Research Institute for Mathematics and Computer Science (CWI) in Amsterdam, The Netherlands.[6] He founded DigiCash, an electronic cash company, in 1990.[1]:119

Chaum received the Information Technology European Award for 1995.[7] In 2004, he was named an IACR Fellow.[8] In 2010, he received during the RSA Conference the RSA Award for Excellence in Mathematics.[9]

Notable research contributions[edit]

Digital cash[edit]

Chaum is credited as the inventor of secure digital cash for his 1982 paper, which also introduced the cryptographic primitive of a blind signature.[10] These ideas have been described as the technical roots of the vision of the Cypherpunk movement that began in the late 1980s.[11] Chaum's proposal allowed users to obtain digital currency from a bank and spend it in a manner that is untraceable by the bank or any other party.[12] In 1988, he extended this idea (with Amos Fiat and Moni Naor) to allow offline transactions that enable detection of double-spending.[13]

In 1990, he founded DigiCash, an electronic cash company, in Amsterdam to commercialize the ideas in his research.[1]:119 The first electronic payment was sent in 1994.[14] In 1999, Chaum left the company.[6]

New types of digital signatures[edit]

In the same 1982 paper that proposed digital cash, Chaum introduced blind signatures.[10] This form of digital signature blinds the content of a message before it is signed, so that the signer cannot determine the content. The resulting blind signature can be publicly verified against the original, unblinded message in the manner of a regular digital signature.[15]

In 1989, he (with Hans van Antwerpen) introduced undeniable signatures.[16] This form of digital signature uses a verification process that is interactive, so that the signatory can limit who can verify the signature. Since signers may refuse to participate in the verification process, signatures are considered valid unless a signer specifically uses a disavowal protocol to prove that a given signature was not authentic.[17]

In 1991, he (with Eugene van Heyst) introduced group signatures, which allow a member of a group to anonymously sign a message on behalf of the entire group.[18] However an appointed group manager holds the power to revoke the anonymity of any signer in the case of disputes.[19]

Anonymous communication[edit]

In 1981, Chaum proposed the idea of an anonymous communication network in a paper.[20] His proposal, called mix networks, allows a group of senders to submit an encryption of a message and its recipient to a server. Once the server has a batch of messages, it will reorder and obfuscate the messages so that only this server knows which message came from which sender. The batch is then forwarded to another server who does the same process. Eventually, the messages reach the final server where they are fully decrypted and delivered to the recipient. A mechanism to allow return messages is also proposed. Mix networks are the basis of some remailers and are the conceptual ancestor to modern anonymous web browsing tools like Tor (based on onion routing). Chaum has advocated that every router be made, effectively, a Tor node.[21]

In 1988, Chaum introduced a different type of anonymous communication system called a DC-Net, which is a solution to his proposed Dining Cryptographers Problem.[22] DC-Nets is the basis of the software tool Dissent.[23]

Trustworthy voting systems[edit]

Chaum has made numerous contributions to secure voting systems, including the first proposal of a system that is end-to-end verifiable. This proposal, made in 1981,[20] was given as an application of mix networks. In this system, the individual ballots of voters were kept private which anyone could verify that the tally was counted correctly. This, and other early cryptographic voting systems, assumed that voters could reliably compute values with their personal computers. In 1991, Chaum introduced SureVote which allowed voters to cast a ballot from an untrustworthy voting system,[24] proposing a process now called "code voting" and used in remote voting systems like Remotegrity.[25]

In 1994, Chaum introduced the first in-person voting system in which voters cast ballots electronically at a polling station and cryptographically verify that the DRE did not modify their vote (or even learn what it was).[26] In the following years, Chaum proposed (often with others) a series a cryptographically verifiable voting systems that use conventional paper ballots: Pret a Voter,[27] Punchscan,[28] and Scantegrity.[29] The city of Takoma Park, Maryland used Scantegrity for its November, 2009 election.[30] This was the first time a public sector election was run using any cryptographically verifiable voting system.[31]

In 2011, Chaum proposed Random Sample Elections.[32] This electoral system allows a verifiably random selection of voters, who can maintain their anonymity, to cast votes on behalf the entire electorate.[33]

Near Eye Display[edit]

A near eye display patent application authored by David Chaum has been updated.[34][35] "PERSPECTIVA - All styles of eyeglasses can be upgraded to overlay, anywhere you can see through them, digital imagary that is of unbeatable quality." "Invented then founded and led an effort that has demonstrated feasibility of a new paradigm for delivering light that digitally deconstructs images so that they can be reconstructed on the retina with dynamic focus and exquisite clarity."[36] This augmented reality technology seems similar to Magic Leap, Hololens, and Oculus.

Other contributions[edit]

In 1979, Chaum proposed a mechanism for splitting a key into partial keys, a predecessor to secret sharing.[37]

In 1985, Chaum proposed the original anonymous credential system,[12] which is sometimes also referred to as a pseudonym system.[38] This stems from the fact that the credentials of such a system are obtained from and shown to organizations using different pseudonyms which cannot be linked.

In 1988, Chaum with Gilles Brassard and Claude Crepeau published a paper[39] that introduced zero-knowledge arguments, as well as a security model using information-theoretic private-channels, and also first formalized the concept of a commitment scheme.

1991, with Torben Pedersen, he demonstrated a well-cited zero-knowledge proof of a DDH tuple.[40] This proof is particularly useful as it can prove proper reencryption of an Elgamal ciphertext.

Chaum contributed to an important commitment scheme which is often attributed to Pedersen. In fact, Pedersen, in his 1991 paper,[41] cites a rump session talk on an unpublished paper by Jurjen Bos and Chaum for the scheme. It appeared even earlier in a paper by Chaum, Damgard, and Jeroen van de Graaf.[42] The scheme is widely used as it is a simple perfectly hiding commitment, that is binding assuming the hardness of the discrete logarithm problem.

In 1993 with Stefan Brands, Chaum introduced the concept of a distance-bounding protocol.[43] Using round-trip delay based on the speed of light, it allows one party to establish an upper-bound on the physical distance from another in an authenticated way.

See also[edit]


  1. ^ a b c Greenberg, Andy (2012). This Machine Kills Secrets: How WikiLeakers, Cypherpunks, and Hacktivists Aim to Free the World's Information. Dutton Adult. ISBN 0525953205.
  2. ^ Danezis, George; Diaz, Claudia (January 2008) "Survey of Anonymous Communication Channels" PDF. Technical Report MSR-TR-2008-35. Microsoft Research; For the paper, see Chaum, David (1981). "Untraceable Electronic Mail, Return Addresses, and Digital Pseudonyms". Communications of the ACM. 24 (2): 84–90. doi:10.1145/358549.358563.
  3. ^ David Lee Chaum. "Computer Systems Established, Maintained and Trusted by Mutually Suspicious Groups." University of California, Berkeley, 1982.
  4. ^ Pitta, Julie (November 1, 1999). "Requiem for a Bright Idea". Forbes.
  5. ^ Blanchette, Jean-François (2012). Burdens of Proof: Cryptographic Culture and Evidence Law in the Age of Electronic Documents. MIT Press. ISBN 026230080X.
  6. ^ a b "Archived copy". Archived from the original on 2013-12-02. Retrieved 2013-06-13.
  7. ^ Rotenberg, Marc (May 1, 1996). "Eurocrats Do Good Privacy". Wired Magazine. Retrieved June 17, 2013.
  8. ^ "IACR Fellows". IACR. Retrieved June 17, 2013.
  9. ^ "Archived copy". Archived from the original on 2013-06-16. Retrieved 2013-06-13.
  10. ^ a b Chaum, David (1983). "Blind signatures for untraceable payments" (PDF). Advances in Cryptology Proceedings of Crypto. 82 (3): 199–203. doi:10.1007/978-1-4757-0602-4_18.
  11. ^ Arvind Narayanan: What Happened to the Crypto Dream?, Part 1. IEEE Security & Privacy. Volume 11, Issue 2, March–April 2013, pages 75-76, ISSN 1540-7993
  12. ^ a b Chaum, David (October 1985). "Security without identification: transaction systems to make big brother obsolete". Communications of the ACM. 28 (10): 1030–1044. doi:10.1145/4372.4373.
  13. ^ Chaum, D.; Fiat, A.; Naor, M. (1990), "Untraceable electronic cash", Proceedings on Advances in cryptology—CRYPTO '88, Lecture Notes in Computer Science, 403, London, UK: Springer-Verlag, pp. 319–327
  14. ^ "Archived copy". Archived from the original on 2015-01-07. Retrieved 2013-06-13.
  15. ^ "Archived copy". Archived from the original on 2012-08-26. Retrieved 2013-06-13.
  16. ^ David Chaum, Hans van Antwerpen: Undeniable Signatures; Crypto'89, LNCS 435, Springer-Verlag, Berlin 1990, 212-216.
  17. ^ "Archived copy". Archived from the original on 2012-08-20. Retrieved 2013-06-13.
  18. ^ Chaum, David; van Heyst, Eugene (1991). "Group signatures" (PDF). Advances in Cryptology — EUROCRYPT ’91. Lecture Notes in Computer Science. 547: 257–265.[permanent dead link]
  19. ^ "Archived copy". Archived from the original on 2012-08-20. Retrieved 2013-06-13.
  20. ^ a b Chaum, D. L. (1981). "Untraceable electronic mail, return addresses, and digital pseudonyms". Communications of the ACM. 24 (2): 84–90. doi:10.1145/358549.358563.
  21. ^ Video on YouTube
  22. ^ David Chaum (1988). "The Dining Cryptographers Problem: Unconditional Sender and Recipient Untraceability". Journal of Cryptology. 1 (1): 65–75. doi:10.1007/BF00206326.
  23. ^ http://korz.cs.yale.edu/2010/anon/
  24. ^ David Chaum (2001), "SureVote: Technical Overview," Proceedings of the Workshop on Trustworthy Elections (WOTE ’01).
  25. ^ Filip Zagorski and Richard T. Carback and David Chaum and Jeremy Clark and Aleksander Essex and Poorvi L. Vora (2013), "Remotegrity: Design and Use of an End-to-End Verifiable Remote Voting System," 11th International Conference on Applied Cryptography and Network Security (ACNS 2013).
  26. ^ Declan McCullagh, "High hopes for unscrambling the vote", CNET News, June 8, 2004.
  27. ^ Chaum, D.; P.Y.A. Ryan; S. Schneider (2005), "A Practical Voter-Verifiable Election Scheme" (PDF), Proceedings of ESORICS 2005, 10th European Symposium on Research in Computer Security: 118–139, archived from the original (PDF) on 2012-03-14
  28. ^ S. Cherry, "Making Every E-Vote Count", IEEE Spectrum, Jan 1 2007.
  29. ^ M. Lafsky, "Protecting Your Vote With Invisible Ink," Discover Magazine, Oct 2008.
  30. ^ Pilot Study of the Scantegrity II Voting System Planned for the 2009 Takoma Park City Election (PDF), archived from the original (PDF) on July 19, 2011
  31. ^ Hardesty, Larry, "Cryptographic voting debuts", MIT news, retrieved 2009-11-30
  32. ^ "http://rs-elections.com/". Archived from the original on 2013-06-23. Retrieved 2013-06-28. External link in |title= (help)
  33. ^ J. Davis. "How Selecting Voters Randomly Can Lead to Better Elections." Wired, 20.05, 2011.
  34. ^ Near to eye display and appliance, retrieved 2015-10-26
  35. ^ Near to Eye Display System and Appliance, retrieved 2015-10-27
  36. ^ "Near to eye display and appliance". Archived from the original on 2016-10-17. Retrieved 2017-01-24.
  37. ^ Chaum, D. (1985). "How to Keep a Secret Alive". Advances in Cryptology. Lecture Notes in Computer Science. 196. pp. 481–485. doi:10.1007/3-540-39568-7_40. ISBN 978-3-540-15658-1.
  38. ^ Lysyanskaya, Anna; Rivest, Ronald L.; Sahai, Amit; Wolf, Stefan (2000). "Pseudonym systems". In Heys, Howard M.; Adams, Carlisle M. Selected Areas in Cryptography. Lecture Notes in Computer Science. 1758. Springer. pp. 184–199. doi:10.1007/3-540-46513-8_14. ISBN 978-3-540-67185-5.
  39. ^ Gilles Brassard, David Chaum, and Claude Crepeau, Minimum Disclosure Proofs of Knowledge, Journal of Computer and System Sciences, vol. 37, pp. 156–189, 1988.
  40. ^ David Chaum and Torben P. Pedersen. 1992. Wallet Databases with Observers. In Proceedings of the 12th Annual International Cryptology Conference on Advances in Cryptology (CRYPTO '92), Ernest F. Brickell (Ed.). Springer-Verlag, London, UK, UK, 89-105.
  41. ^ Pedersen, T. P. (1992). "Non-Interactive and Information-Theoretic Secure Verifiable Secret Sharing". Advances in Cryptology — CRYPTO '91. Lecture Notes in Computer Science. 576. pp. 129–140. doi:10.1007/3-540-46766-1_9. ISBN 978-3-540-55188-1.
  42. ^ Chaum, D.; Damgård, I. B.; Graaf, J. (1988). "Multiparty Computations Ensuring Privacy of Each Party's Input and Correctness of the Result". Advances in Cryptology — CRYPTO '87. Lecture Notes in Computer Science. 293. p. 87. doi:10.1007/3-540-48184-2_7. ISBN 978-3-540-18796-7.
  43. ^ Stefan Brands, David Chaum: Distance-bounding protocols (extended abstract). Proceedings Eurocrypt '93.

Further reading[edit]

External links[edit]