SOLDI: Secure off-line disposable credits to secure mobile micro payments

Mobile-based payment schemes are increasingly widespread albeit suffering from a number of limitations. In fact, current proto- cols require at least one of the two parties to be on-line, i.e. connected either to a trusted third party or to a shared database. In particular, in scenarios where customers and vendors are persistently or intermit- tently disconnected from the network, no on-line payment is possible. This paper discusses SOLDI, a novel mobile micro-payment approach where all involved parties can be fully off-line. SOLDI relies solely on local data to perform the requested operations and improves over state- of-the-art approaches in terms of payment flexibility and security. SOLDI architecture and protocols are discussed in depth in this paper. Finally, security properties and main functionalities are analyzed in depth, show- ing SOLDI viability, benefits, and further development directions.