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)
  • Parts 2+: 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  Demo code: Recipe book (outdated) • LAN electron (outdated) • LAN localhost server (outdated)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

• The Art of the Fugue: Minimizing Interleaving in Collaborative Text Editing.
  M. Weidner, J. Gentle, 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
• Collabs: Composable Collaborative Data Structures.
  M. Weidner, H. Miller, H. Qi, M. Kjaer, R. Pradeep, B. Geordie, and C. Meiklejohn. arXiv preprint, 2022.
  arXiv
• 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