Asymptotic Analysis of Plausible Tree Hash Modes for SHA-3

Discussions about the choice of a tree hash mode of operation for a standardization have recently been undertaken. It appears that a single tree mode cannot address adequately all possible uses and specifications of a system. In this paper, we review the tree modes which have been proposed, we discuss their problems and propose remedies. We make the reasonable assumption that communicating systems have different specifications and that software applications are of different types (securing stored content or live-streamed content). Finally, we propose new modes of operation that address the resource usage problem for the three most representative categories of devices and we analyse their asymptotic behavior

Protecting Quantum Procrastinators with Signature Lifting: A Case Study in Cryptocurrencies

Current solutions to quantum vulnerabilities of widely used cryptographic schemes involve migrating users to post-quantum schemes before quantum attacks become feasible. This work deals with protecting quantum procrastinators: users that failed to migrate to post-quantum cryptography in time. To address this problem in the context of digital signatures, we introduce a technique called signature lifting, that allows us to lift a deployed pre-quantum signature scheme satisfying a certain property to a post-quantum signature scheme that uses the same keys. Informally, the said property is that a post-quantum one-way function is used somewhere along the way to derive the public-key from the secret-key. Our constructions of signature lifting relies heavily on the post-quantum digital signature scheme Picnic (Chase et al., CCS\u2717). Our main case-study is cryptocurrencies, where this property holds in two scenarios: when the public-key is generated via a key-derivation function or when the public-key hash is posted instead of the public-key itself. We propose a modification, based on signature lifting, that can be applied in many cryptocurrencies for securely spending pre-quantum coins in presence of quantum adversaries. Our construction improves upon existing constructions in two major ways: it is not limited to pre-quantum coins whose ECDSA public-key has been kept secret (and in particular, it handles all coins that are stored in addresses generated by HD wallets), and it does not require access to post-quantum coins or using side payments to pay for posting the transaction

Security analysis of hardware crypto wallets

Tato práce analyzuje bezpečnost moderních hardwarových krypto peněženek. Různé modely ohrožení a hrozby jsou zhodnoceny. Několik současných hardwarových peněženek je podrobeno recenzi. Potenciální uživatelé jsou poučeni o tom, jak vybrat správnou hardwarovou peněženku a na nekalé praktiky některých výrobců. Původní hardwarová peněženka, Trezor One, je podrobena detailní analýze jak z hardwarové, tak softwarové perspektivy a tvrzení výrobce jsou ověřena. Zvláštní důraz je kladen na útoky postranním kanálem a experimenty s Trezor One.The thesis analyzes the security of modern hardware crypto wallets. Different threat models and threats for users are assessed with some of the current hardware wallets reviewed. Potential users are educated how to choose the right hardware wallet and warned about misleading advertising of some vendors. The original hardware wallet, Trezor One, is thoroughly analyzed from both hardware and software perspective and the security claims of the vendor are verified. A particular emphasis is placed on side-channel attacks and experiments with Trezor One