Complex Revocation Conditions Sample Clauses

Complex Revocation Conditions. While the majority of prior work on data revocation simply use time-based ex- piration mechanisms, we suppose that smart contracts can be used to create almost arbitrary expiration conditions. However, these conditions need to be objectively observable through reliable data sources providing appropriate in- terfaces. Such scenarios would require an additional step in the verification step of our protocol, whereas the general procedure would be similar and security requirements would not be stricter than for the data access verification. In a na¨ıve approach, the expiration condition is represented as an expression in natural language. There is a need for reliable information sources that are capable of processing the information in their represented form, e. g. providing an interface for natural-language processing. The trust in these services (e. g., Google, Wikipedia, Wolfram Alpha) can be reduced through the use of decen- tralized verification as proposed by ChainLink, assuming that the service cannot distinguish verification attempts from regular requests to their services. In addi- tion, the stability of information must be taken into account, i. e., the verification must be resilient to short-time changes, e. g., malicious users manipulating the information to their advantage and then triggering the settlement process. This is feasible, if Wikipedia is used as a knowledge base, but can be prevented by also considering the information history. However, with more complex expiration conditions, we also see the possibility that data items can become valid again after they have expired. Examples are scenarios in which data are supposed to be available only on specific days of the week, or have a daily access limit (under the assumption that the number of accesses can be verified reliably). This property makes the use of smart contracts a much more powerful instrument than previous approaches.