Sirvi Autor "Krips, Toomas, juhendaja" järgi

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Always Two, There Are: Towards Two-Party SDitH
(Tartu Ülikool, 2025) Veri, Hans Kristjan; Krips, Toomas, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
The rise of quantum computing threatens to break many of the cryptographic systems that secure today’s digital world. In response, researchers are developing new tools designed to remain secure in a post-quantum future. Most of the promising candidates for post-quantum digital signatures rely on security assumptions based on lattices or properties of hash functions. Another promising approach transforms secure multi-party computation protocols into zero-knowledge proofs, which are then turned into digital signatures. This technique, known as multi-party computation in-the-head (MPCitH), offers strong security properties and flexibility for distributed applications. This thesis investigates whether MPCitH digital signatures can be efficiently adapted for use by two cooperating parties to jointly produce a signature. Here we show how to construct two-party signatures based on syndrome decoding in-the-head (SDitH) signatures. We propose a provably secure scheme that achieves the smallest known communication overhead among two-party MPCitH signatures, while resulting in a signature size approximately double that of a single-prover variant. This result provides a new data point in the design space of multi-party MPCitH signatures and post-quantum digital signatures in general.
Design and Security Analysis of Blind Smart-ID/SplitKey Signature
(Tartu Ülikool, 2025) Karu, Mihkel Jaas; Snetkov, Nikita, juhendaja; Laud, Peeter, juhendaja; Krips, Toomas, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
A blind signature scheme is a cryptographic primitive that enables a user to obtain a signature on a message without revealing its content to the signer. This unique property ensures both the authenticity of the signature and the privacy of the message, making blind signatures particularly useful in applications requiring anonymity, such as electronic voting and digital cash systems. SplitKey [BKLO17] is a cryptographic technology designed to enable the creation of digital signatures using a private key distributed across two devices. However, it currently lacks support for blind signing. The goal of this thesis is to determine whether the original SplitKey design can be modified to create a blind signature scheme, and to explore how it could be done. To achieve this, the thesis presents a novel blind signature scheme, RSA-BSK, which extends the functionality of the SplitKey signature scheme to support blind signatures. We provide a detailed security analysis of RSA-BSK, including formal proofs of correctness, unforgeability, and blindness, thus establishing its suitability for privacy-preserving applications in a distributed key setting.
Efficient Two-Party ML-DSA Protocol in Active Security Model
(Tartu Ülikool, 2025) Kravtšenko, Semjon; Laud, Peeter, juhendaja; Krips, Toomas, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
ML-DSA is a NIST standard that defines a signature scheme: a set of algorithms for creating and verifying digital signatures. Digital signatures can be used, for example, to authenticate to websites online and to sign documents. ML-DSA signatures, unlike signatures that follow so-called classical formats, are quantum-resistant: it is believed that forging ML-DSA signatures is inviable even with a cryptographically relevant quantum computer (that is not yet known to exist). The security of a signing scheme relies on the secrecy of the used private key material. One way to increase the security of a signing scheme is to distribute the secret material across multiple devices, such that a sufficient number of them need to cooperate to create a signature. One scheme, that distributes the key across two devices, is implemented in SplitKey® technology, which is used in a popular signing solution Smart-ID®. Unfortunately, a two-party scheme that could create standards-compliant quantum-resistant signatures does not exist. This thesis presents a novel two-party signing scheme capable of creating ML-DSA-compliant signatures — Duolithium. This scheme is resistant against potential active attacks by either party, both during the key generation and signing processes. The thesis proposes some parts of Duolithium that were invented as a part of this thesis research and documents the remaining parts with reliance on prior research. Additionally, this thesis presents a complete, tested for functionality implementation of Duolithium in Python, together with the results of the benchmarks of network overhead and computational performance. The benchmark results suggest that Duolithium may be used to implement a new, quantum-resistant version of SplitKey that would be fully compatible with any signature verification component that supports ML-DSA.
Manimi abil loodud õppevideod põhikooli matemaatikast
(Tartu Ülikool, 2025) Suuder, Joosep; Ain, Kati, juhendaja; Krips, Toomas, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
The purpose of this bachelor's thesis is to create mathematics educational videos for the elementary school level using the Manim library of the Python language. The created videos are meant to support the teaching of concepts that are handled in the primary school curriculum, using visual elements to aid in the memorization and understanding of the aforementioned. This work explores the nature of visual learning, sets goals and requirements for the created videos, gives an overview of the used technologies and analyzes the results.
Two-Party Multi-Point Function Secret Sharing
(Tartu Ülikool, 2024) Külaots, Erki; Krips, Toomas, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
Turvaline ühisarvutus on tähtis krüptograafia haru, mis tegeleb privaatsete andmete töötlemisega. Üks oluline komponent turvalises ühisarvutuses on korreleeritud juhuslikkus, mis aitab osapooltel teha arvutusi efektiivsemalt või vähendada nendevahelise suhtluse mahtu, säilitades seejuures andmete privaatsust. Mõned näited sellisest korreleeritud juhuslikkusest on juhuslikud pimeedastusseosed (OT), lineaarfunktsiooni pimeväärtustamisseosed (OLE), Beaveri kolmikud ja ühekordsed tõeväärtustabelid. Mitmikpunktfunktsiooni saladusejaostust saab edukalt kasutada (pseudo)juhuslike seoste genereerimisel. Sellest tulenevalt tekib küsimus, et kuidas saame konstrueerida efektiivset mitmikpunktfunktsiooni saladusejaostusskeemi. Käesolevas magistritöös läheneme me sellele küsimusele uutmoodi, kasutades puu struktuuri, pseudojuhuarvude generaatorit ja lineaarvõrrandisüsteeme. Meie skeem MultiFunUSLESS on efektiivsuselt võrreldav varasemate konstruktsioonidega ja on väärtustamisfaasis neist kiireim. Seega on see teatud kasutusjuhtudel parim valik. MultiFunUSLESS võimaldab meil mitmikpunktfunktsiooni saladusejaotusskeemi konstrueerimisele läheneda uutviisi. Arvutiteaduses on efektiivsus võtmesõnaks – algoritmid peaksid arvutama kiiremini, kasutama vähem ressursse ja suhtlus peaks olema minimaalne. See ongi käesoleva magistritöö eesmärk.