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Invited Talks

Daniele Cozzo

Tuesday, January 25, 2022

11:00am Lecture hall 1 & Zoom3 https://zoom.us/j/3911012202 (pass: s3)

Daniele Cozzo, PhD Student, KU Leuven, Belgium

Gladius: LWR-based efficient hybrid public key encryption with distributed decryption

Abstract:

Standard hybrid encryption schemes based on the KEM-DEM framework are hard to implement efficiently in a distributed manner while maintaining the CCA security property of the scheme. This is because the DEM needs to be decrypted under the key encapsulated by the KEM, before the whole ciphertext is declared valid. In this paper we present a new variant of the KEM-DEM framework, closely related to Tag-KEMs, which sidesteps this issue. We then present a post-quantum KEM for this framework based on Learning-with-Rounding, which is designed specifically to have fast distributed decryption. Our combined construction of a hybrid encryption scheme with Learning-with-Rounding based KEM, called Gladius, is closely related to the NIST Round 3 candidate called Saber. We wrote prototype distributed implementation that achieves a decapsulation time of 4.99 seconds for three parties.


Time and place:
11:00am Lecture hall 1 & Zoom3 https://zoom.us/j/3911012202 (pass: s3)
IMDEA Software Institute, Campus de Montegancedo
28223-Pozuelo de Alarcón, Madrid, Spain


Hamza Abusalah

Monday, January 10, 2022

11:30am Zoom9 - https://zoom.us/j/9911012202 (pass: s3)

Hamza Abusalah, Post-doctoral Researcher, Vienna University of Technology, Austria

SNACKs: Leveraging Proofs of Sequential Work for Blockchain Light Clients

Abstract:

We revisit the problem of designing light-client blockchain protocols from the perspective of classical proof-system theory. This results in a framework that allows quantifying the security guarantees provided to a light-client verifier even when interacting only with a single dishonest (full-node) prover. We define a new primitive called succinct non-interactive argument of chain knowledge (SNACK) capturing this intuition and show how augmenting any blockchain with a graph-labeling proof of sequential work (GL-PoSW) enables SNACK proofs for this blockchain. We also provide a unified and extended definition of GL-PoSW covering all existing constructions and describe a new variant. We then show how SNACKs can be used to construct light-client protocols, and highlight some deficiencies of existing solutions. (Joint work with: Georg Fuchsbauer, Peter Gazi, and Karen Klein)


Time and place:
11:30am Zoom9 - https://zoom.us/j/9911012202 (pass: s3)
IMDEA Software Institute, Campus de Montegancedo
28223-Pozuelo de Alarcón, Madrid, Spain


Invited Talks - 2021