Traditionally, mobile wallets rely on a trusted server that provides them with a current view of the blockchain, and thus, these wallets do not need to validate the header chain or transaction inclusion themselves. If a mobile wallet were to validate a header chain and inclusion of its transactions, it would require significant storage and performance overhead, which is challenging and expensive to ensure on resource-limited devices, such as smartphones. Moreover, such an overhead would be multiplied by the number of cryptocurrencies the user holds.Therefore, we introduce a novel approach, called SNARKlet, to mobile wallet synchronization designed to eliminate trust in a server while providing efficient utilization of resources. Our approach addresses the challenges associated with storage and bandwidth requirements by off-chaining validation of header chains using SNARK-based proofs of chain extension, which are verified by a smart contract. This offers us a means of storing checkpoints in header chains of multiple blockchains.The key feature of our approach is the ability of mobile clients to update their partial local header chains using checkpoints derived from the proof verification results stored in the smart contract. In the evaluation, we created zk-SNARK proofs for the 2, 4, 8, 16, 32, and 64 headers within our trustless off-chain service. For 64-header proofs, the off-chain service producing proofs requires at least 40 GB of RAM, while minimal gas consumption is achieved for 12 proofs bundled in a single transaction. We achieved a 20-fold reduction in storage overhead for a mobile client in contrast to traditional SPV clients. Although we have developed a proof-of-concept for PoW blockchains, the whole approach can be extended in principle to other consensus mechanisms, e.g., PoS.

In this work, we review existing cryptocurrency wallet solutions with regard to authentication methods and factors from the user’s point of view. In particular, we distinguish between authentication factors that are verified against the blockchain and the ones verified locally (or against a centralized party). With this in mind, we define notions for k-factor authentication against the blockchain and k-factor authentication against the authentication factors. Based on these notions, we propose a classification of authentication schemes. We extend our classification to accommodate the threshold signatures and signing transactions by centralized parties (such as exchanges or co-signing services). Finally, we apply our classification to existing wallet solutions, which we compare based on various security and key-management features.

This paper focuses on the problem of detection and prevention of stolen and misused secrets (such as private keys) for authentication toward centralized services. We propose a solution for this problem, based on SmartOTPs, the two-factor authentication scheme against the blockchain, which is intended for smart contract wallets and utilizes one-time passwords (OTPs). We modify SmartOTPs for our purposes and utilize them in the setting of two-and-a-half-factor authentication against a centralized service provider. Out of two and a half factors of our solution, the first factor stands for the private key, and the second and a half factor stands for OTPs and their precursors (a.k.a., pre-images), where OTPs are obtained from the precursors by cryptoaraphically secure hashing. We describe the protocol for bootstrapping our approach as well as the authentication procedure. In the case of stolen creden-tials from the client, we show that our solution enables the user to immediately detect it and proceed to re-initialization with fresh credentials. We utilize blockchain-based identity management and decentralized identities of users to simplify the overhead of the registration process and reinitialization.

In late 2022, OpenAI released a new version of ChatGPT, a sophisticated natural language processing system capable of holding natural conversations while preserving and responding to the context of the discussion. ChatGPT has exceeded expectations in its abilities, leading to extensive considerations of its potential applications and misuse. In this work, we evaluate the influence of ChatGPT on university education, with a primary focus on computer security-oriented specialization. We gather data regarding the effectiveness and usability of this tool for completing exams, programming assignments, and term papers. We evaluate multiple levels of tool misuse, ranging from utilizing it as a consultant to simply copying its outputs. While we demonstrate how easily ChatGPT can be used to cheat, we also discuss the potentially significant benefits to the educational system. For instance, it might be used as an aid (assistant) to discuss problems encountered while solving an assignment or to speed up the learning process. Ultimately, we discuss how computer science higher education should adapt to tools like ChatGPT.