Matthew Weidner CMU (current, PhD in CS) Cambridge ('19, MPhil in CS) Caltech ('18, BS in Math)

I am a computer science PhD student at CMU, advised by Heather Miller. For most of my PhD, I was supported by an NDSEG Fellowship sponsored by the US Office of Naval Research.

My current research focuses on tools for building decentralized systems, including conflict-free replicated data types (CRDTs) and secure group messaging protocols. Previously, I studied error-correcting code algorithms and algebraic number theory.

Blog

• CRDT Survey (Series):
  • Part 1: Introduction (2023/09/26)
  • Part 2: Semantic Techniques (2023/10/17)
  • Parts 3+: In progress
• "Position Strings" for Collaborative Lists and Text (2023/04/13)
• Fugue: A Basic List CRDT (2022/10/21)
• Designing Data Structures for Collaborative Apps (2022/02/10)

RSS Feed

Open-Source Software

• Collabs: A TypeScript collections library for collaborative data structures.
• position-strings: A source of lexicographically-ordered "position strings" for collaborative lists and text.

Talks

• Using and implementing collaborative data structures with Collabs.
  Local First Web Meetup #5, 6/27/2023.
  Video • Slides • Live demo
  Demo code: Recipe editor over Dropbox
• Designing for Eventual Consistency with Simple, Composable CRDTs.
  UCSC Languages, Systems, and Data Seminar, 2/18/2022.
  Slides • Blog post
• Collaborative Apps over Matrix using the Collabs Library.
  Lightning talk at FOSDEM 2022 - Matrix.org Foundation & Community devroom.
  Talk page • Slides
• Making Webapps Collaborative with Composable CRDTs.
  M. Weidner and H. Miller. Strange Loop 2021.
  Talk page • Video • Slides
  Demo code: Recipe book (outdated) • LAN electron (outdated) • LAN localhost server (outdated)

Demo Apps

• Collabs demos: Collaborative apps using the Collabs library.
  Source
• Firebase text editor: A collaborative (plain) text editor using position-strings on top of Firebase RTDB.
  A demo that text CRDTs are not just for local-first apps.
  Source
• Poster session: 3D world with proximity audio and interactive posters & whiteboards.
  Toy app using WebGL, WebRTC, and Collabs's non-CRDT data structures.

Research Papers

Collaborative Apps / CRDTs

• Collabs: A Flexible and Performant CRDT Collaboration Framework.
  M. Weidner, H. Qi, M. Kjaer, R. Pradeep, B. Geordie, Y. Zhang, G. Schare, X. Tang, S. Xing, and H. Miller. arXiv preprint, 2023.
  arXiv
• Proposal: Versioned Collaborative Documents.
  M. Weidner. PLF Workshop 2023.
  preprint • slides
• The Art of the Fugue: Minimizing Interleaving in Collaborative Text Editing.
  M. Weidner and M. Kleppmann. arXiv preprint, 2023.
  arXiv
• For-Each Operations in Collaborative Apps.
  M. Weidner, R. Pradeep, B. Geordie, and H. Miller. PaPoC 2023.
  Official (open access) • arXiv (extended version) • Slides
• Programmer Experience When Using CRDTs to Build Collaborative Webapps: Initial Insights.
  Y. Zhang, M. Weidner, and H. Miller. PLATEAU 2023.
  Official (open access) • Slides
• An Oblivious Observed-Reset Embeddable Replicated Counter.
  M. Weidner and P. S. Almeida. PaPoC 2022.
  Official (open access) • Slides
• Composing and Decomposing Op-Based CRDTs with Semidirect Products.
  M. Weidner, H. Miller, and C. Meiklejohn. ICFP 2020.
  Official (open access) • Video • Slides (ICFP 2020) • Slides (SPLASH 2022)

Secure Messaging

• Key Agreement for Decentralized Secure Group Messaging with Strong Security Guarantees.
  M. Weidner, M. Kleppmann, D. Hugenroth, and A. R. Beresford. ACM CCS '21.
  Extended version • Official (open access)
• Group messaging for secure asynchronous collaboration.
  M. Weidner. University of Cambridge MPhil Dissertation, 2019.
  Advisors: A. R. Beresford and M. Kleppmann.
  Pdf

Math and CS Theory (Older)

• On decoding Cohen-Haeupler-Schulman tree codes.
  A. K. Narayanan and M. Weidner. SODA 2020.
  Pdf • Official • Slides
• Subquadratic time encodable codes beating the Gilbert-Varshamov bound.
  A. K. Narayanan and M. Weidner. IEEE Transactions on Information Theory, October 2019.
  Pdf (authors' accepted manuscript) • Official
• On cycles of pairing-friendly elliptic curves.
  A. Chiesa, L. Chua, and M. Weidner. SIAM Journal on Applied Algebra and Geometry, 2019.
  Pdf • Official
• Pseudocharacters of homomorphisms into classical groups.
  M. Weidner. Transformation Groups, 2020.
  Pdf (author's accepted manuscript) • Offical
• On conjectural rank parities of quartic and sextic twists of elliptic curves.
  M. Weidner. International Journal of Number Theory, June 2019.
  arXiv • Official • Code
• Towards fast encoding of Garcia-Stichtenoth algebraic geometry codes.
  M. Weidner. Caltech SURF Final Report, 2018.
  Advisors: A. K. Narayanan and C. Umans.
  Pdf
• On Selmer rank parity of twists.
  M. Hadian and M. Weidner. Journal of the Australian Mathematical Society, June 2017.
  Pdf (preprint) • Official

CV

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Matthew Weidner • PhD student at CMU CSD • maweidne@andrew.cmu.edu • @MatthewWeidner3