Fwd: Alin Tomescu on Nov 16 -- UTT: Sensibly-Anonymous Decentralized Payments from Rerandomizable Signatures

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Alan Karp

Nov 10, 2023, 5:22:16 PM11/10/23
to cap-...@googlegroups.com, <friam@googlegroups.com>
Nothing about capabilities, but I believe some of you are interested in e-cash.  The talks in this series are usually crypto-heavy.  You've been warned!

Alan Karp

---------- Forwarded message ---------
From: Aditi Partap <adit...@stanford.edu>
Date: Fri, Nov 10, 2023 at 11:01 AM
Subject: Alin Tomescu on Nov 16 -- UTT: Sensibly-Anonymous Decentralized Payments from Rerandomizable Signatures
To: security...@lists.stanford.edu <security...@lists.stanford.edu>

    UTT: Sensibly-Anonymous Decentralized Payments from

                 Rerandomizable Signatures

                        Alin Tomescu

                Thursday, November 16, 2023

                       Talk at 4:00pm

                      Gates 259 & Zoom (https://stanford.zoom.us/j/92732897040?pwd=Q29JOFVFSy9kWXVDR3dIVWlGektFdz09)

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We present UTT, a system for decentralized ecash with accountable


UTT is the first ecash system that obtains three critical properties:

(1) it provides decentralized trust by implementing the ledger, bank,

auditor, and registration authorities via threshold cryptography and

Byzantine Fault Tolerant infrastructure; (2) it balances accountability

and privacy by implementing anonymity budgets: users can anonymously

send payments, but only up to a limited amount of currency per month.

Past this point, transactions can either be made public or subjected to

customizable auditing rules; (3) by carefully choosing cryptographic

building blocks and co-designing the cryptography and decentralization,

UTT is tailored for high throughput and low latency.  With a combination

of optimized cryptographic building blocks and vertical scaling

(optimistic concurrency control), UTT can provide almost 1,000 payments

with accountable privacy per second, with latencies of around 100

milliseconds and less.  Through horizontal scaling (multiple shards),

UTT can scale to tens of thousands of such transactions per second.

With 60 shards we measure over 10,000 transactions with accountable

privacy per second, with latencies around 500 milliseconds.

We formally define and prove the security of UTT using an MPC-style

ideal functionality.  Along the way, we define a new MPC framework that

captures the security of reactive functionalities in a stand-alone

setting, thus filling an important gap in the MPC literature.  Our new

framework is compatible with practical instantiations of cryptographic

primitives and provides a trade-off between concrete efficiency and

provable security that may be also useful for future work.


Alin is a Cryptography Research Scientist at Aptos Labs.  He received

his PhD from MIT in 2020.

Alin's research focus is on designing, proving and implementing new

cryptographic primitives for real-world use, focusing on authenticated

data structures, threshold cryptography and sensibly-anonymous payment


Alin was previously a Research Scientist at VMware, where he mostly

worked on vector commitments and anonymous payments for central banking.

Before his PhD work, he was Head of Research & Development at Private

Machines, where he worked on building tamper-proof clouds.

Alin often muses about cryptography (and other fantastic beasts) over at

https://alinush.github.io/.  His favorite thing in the world is

motorcycling through beautiful, sunny California while listening to

out-of-this-world music in the background.

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