| Cryptography |
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Strongly unforgeable digital signatures resilient to polynomially hard-to-invert leakage
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Cryptographic leakage-resilience, which guarantees that the security is retained even if some information related to
private information such as secret-key are partially leaked, is practically meaningful. In this work, we proposed
digital signature schemes which achieve stronger security (i.e., strong existential unforgeability) in an environment
where more various leakage (i.e., polynomially hard-to-invert leakage) can occur than existing schemes.
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Relations among Notions of Security under Replayable CCA Environment for PKE
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RCCA security was introduced by Canetti et al, and it is known as a relaxed
variant of CCA security. RCCA security is useful security notion for
many practical applications such as authentication and key exchange.
They defined NM-RCCA, but their definition of NM-RCCA is not a natural extension of NM-CCA, and the validity of their definition is not
clear.
In this research, we introduce definitions of simulation-based non-malleability and indistinguishability-based
non-malleability against RCCA.
We then prove the equivalence of them.
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Conversions of Verifiable Sharing Protocols in Secure Computation
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Several researches show that secure computation protocols can be converted to each other and be implement together as a
mixed protocol to increase the efficiency of some algorithms. I proposed an approach of conversions with verifiable
sharing protocols based on SPDZ protocol. The SPDZ protocols can help parties to verify the shared value hold by others
in arithmetic sharing. The conversion approach can keep the security level of the shared values while being converted to
other types of sharing protocols.
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| Cryptocurrency |
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An Analysis of Anonymous Cryptocurrency Architectures and its Application
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Enhancing privacy is one of the essential requirements for cryptocurrencies. We are studying architectures of
representative anonymous cryptocurrencies, analyzing a trade-off between significant features such as anonymity,
scalability, and usability, and considering its application.
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A Survey on Micropayment Channels for Cryptocurrencies
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A blockchain, which is an underlying system of cryptocurrencies, cannot deal with lots of transactions per unit time.
Micropayment channels where two parties exchange their funds outside of the blockchain have been proposed to tackle this
scalability problem. In this survey, I'll introduce some techniques used in micropayment channels.
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| Distributed ledger |
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Security proof of POW-type blockchain
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Blockchain is a distributed ledger technology, which has a potential to construct multiparty consensus protocols without a trusted third party. This technology is spreading to apply such as cryptocurrencies and others. Bitcoin adopts a blockchain with proof-of-work (POW). We introduce a security proof of such blockchain, and resulting implications.
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| Anti-malware |
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Dynamic analysis of malicious scripts
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Malicious scripts have been widely used by recent attackers. Dynamic
analysis, which observes behavior of suspicious scripts during
execution, is a promising countermeasure for them. However, manually
building dynamic analysis tools for scripts is almost impossible because
it requires unrealistic efforts of skilled reverse-engineers to know
internal implementation of the corresponding script engines. In this
research, we propose a method for generating dynamic analysis tools by
automatically reverse-engineering script engines.
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Digital forensics
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Android digital forensics
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These days digital forensic techniques, including acquiring data from
digital divices and analyzing the data, are becoming important more and
more.
We introduce recent research, focusing on Android digital forensics.
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