He is known as a pioneer in cryptography and privacy-preserving technologies, and widely recognized as the inventor of digital cash.

His 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups" is the first known proposal for a blockchain protocol.

[1] Complete with the code to implement the protocol, Chaum's dissertation proposed all but one element of the blockchain later detailed in the Bitcoin whitepaper.

[4]: 65–70  His 1981 paper, "Untraceable Electronic Mail, Return Addresses, and Digital Pseudonyms", laid the groundwork for the field of anonymous communications research.

Chaum is credited as the inventor of secure digital cash for his 1983 paper, which also introduced the cryptographic primitive of a blind signature.

[21] In 1988, he extended this idea (with Amos Fiat and Moni Naor) to allow offline transactions that enable detection of double-spending.

[28] However an appointed group manager holds the power to revoke the anonymity of any signer in the case of disputes.

[30] His proposal, called mix networks, allows a group of senders to submit an encryption of a message and its recipient to a server.

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).

[31] 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.

[39] In the following years, Chaum proposed (often with others) a series a cryptographically verifiable voting systems that use conventional paper ballots: Prêt à Voter,[40] Punchscan,[41] and Scantegrity.

[43] This was the first time a public sector election was run using any cryptographically verifiable voting system.

[49] 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 Crépeau published a paper[50] 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.

[55] In July 2024, Chaum sat down with Vitalik Buterin, co-founder of Ethereum for a panel on the future of privacy at Plasmacon conference at the United Nations University in Tokyo, Japan.