A Scalable and Intrusion-tolerant Digital Time-stamping System

Secure digital time-stamps play a crucial role in many applications that rely on the correctness of time-sensitive information. Well-known time-stamping systems are based on linking schemes which provide a relative temporal order by linking requests together. Unfortunately, these schemes do not scale well to large volume of requests, and have coarse granularity and high latency. Therefore, they are unsuitable for very large and dynamic systems, or applications requiring fine-grained and short-lived timestamps, or timeliness, such as stock trading, e-auctions, financial applications, aggregation of real-time sensitive information, and temporal access control. We propose a different scheme, based on real-time timestamps, which overcomes those drawbacks and leads to a performance enhancement. Our time-stamping system is intrusion-tolerant and it is based on a novel robust time service suitable for very large populations, on a robust threshold signature scheme, and on quorum system techniques. We prove its correctness and liveness, and compare its computational and communication complexity to the complexity of tree-based linking scheme. Finally, we show how the fine-granularity, improved scalability and efficiency of our scheme make it particularly suitable to those applications mentioned above, and also to mobile e-commerce.