[crypto] Fwd: [risc-list] RISC at CWI (Wed Jan 24): Cryptography in a Quantum World

[R. Hirschfeld]

-------- Original Message --------
Subject: [risc-list] RISC at CWI (Wed Jan 24): Cryptography in a Quantum 
World
Date: 2024-01-17 15:36
 From: Serge Fehr <fehr at cwi.nl>
To: risc-list at cwi.nl

Dear Colleagues,

we are excited to announce our next RISC seminar, on the occasion of the 
PhD defense of Jelle Don (see Post-Scriptum 2). The topic of the seminar 
will be:

              *Cryptography in a Quantum World*

and the event will be taking place at CWI Amsterdam next week on

      *Wednesday January 24, 2024, in Room L017*

starting at *14:00h* .

The schedule is as follows (see Post-Scriptum 1 below for the 
abstracts):

14:00 - 14:45 Jelle Don (Centrum Wiskunde & Informatica, Cryptology 
group): (New) applications of the measure-and-reprogram technique
14:45 - 15:00 break
15:15 - 15:45 Florian Speelman (University of Amsterdam & QuSoft): 
Relating non-local quantum computation to information theoretic 
cryptography
15:45 - 16:00 break
16:00 - 16:45 Dominique Unruh (University of Tartu & RWTH Aachen 
University): Towards compressed permutation oracles

NB, the RISC web page https://projects.cwi.nl/crypto/risc.php is 
currently not working (we are looking into the matter).

See you then and there!

Best regards,
- Serge Fehr and Ronald Cramer


Post-Scriptum 1

These are the abstracts:

Jelle Don. (New) applications of the measure-and-reprogram technique:

The measure-and-reprogram technique (Don, Fehr, Majenz and Schaffner, 
Crypto 2019) is a proof technique for security reductions in the quantum 
random-oracle model (QROM). In the original application, the technique 
is used to prove the Fiat-Shamir transformation secure in the QROM. For 
the FS reduction, we need to inject a challenge from the sigma-protocol 
challenger into one of the adversary's queries (chosen at random), and 
hope that the adversary will solve the challenge for us. In the QROM, 
apart from reprogramming the oracle, this strategy requires us to 
measure the chosen query. The obstacle to overcome here is then the 
disturbance to the adversary's quantum state caused by the measurement, 
which in general makes it hard to predict the adversary's behavior from 
the measurement on.
In this talk we will recap the technique and give an intuition for why, 
in the right context, we are able to bound the disturbance mentioned 
above. We will then highlight some more recent results that apply the 
technique in a conceptually novel way. In particular, we will see that 
it can be applied in contexts where challenge injection is not the goal.

Florian Speelman. Relating non-local quantum computation to information 
theoretic cryptography: Abstract TBA.

Dominique Unruh. Towards compressed permutation oracles:

Compressed oracles (Zhandry, Crypto 2019) are a powerful technique to 
reason about quantum random oracles, enabling a sort of lazy sampling in 
the presence of superposition queries. A long-standing open question is 
whether a similar technique can also be used to reason about random 
(efficiently invertible) permutations.
In this work, we make a step towards answering this question. We first 
define the compressed permutation oracle and illustrate its use. While 
the soundness of this technique (i.e., the indistinguishability from a 
random permutation) remains a conjecture, we show a curious 2-for-1 
theorem: If we use the compressed permutation oracle methodology to show 
that some construction (e.g., Luby-Rackoff) implements a random 
permutation (or strong qPRP), then we get the fact that this methodology 
is actually sound for free.


Post-Scriptum 2

For those also interested in attending the PhD defense of Jelle Don, the 
information follows:

Date:   Tuesday January 23, 2024
Time:   15:00 - 16:00
Place:  Academiegebouw, Rapenburg 73, 2311 GJ Leiden
Livestream: 
https://www.universiteitleiden.nl/wetenschappers/livestream-promotie
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