(Short Paper) Towards More Reliable Bitcoin Timestamps Pawel Szalachowski SUTD
[email protected] Abstract—Bitcoin provides freshness properties by forming a a timestamping service, and which impacts the security of the blockchain where each block is associated with its timestamp and protocol [11]. the previous block. Due to these properties, the Bitcoin protocol is being used as a decentralized, trusted, and secure timestamping In this work, we propose a new mechanism for improving service. Although Bitcoin participants which create new blocks the security of Bitcoin timestamps. In our protocol, external cannot modify their order, they can manipulate timestamps timestamp authorities can be used to assert a block creation almost undetected. This undermines the Bitcoin protocol as a time, instead of solely trusting timestamps put by block reliable timestamping service. In particular, a newcomer that creators. Our scheme is efficient, simple, practical, does not synchronizes the entire blockchain has a little guarantee about require any additional infrastructure nor any changes to the timestamps of all blocks. Bitcoin protocol, thus can be deployed today. Interestingly, In this paper, we present a simple yet powerful mechanism currently existing SSL/TLS servers can act as time authorities. that increases the reliability of Bitcoin timestamps. Our protocol can provide evidence that a block was created within a certain II. BACKGROUND AND PRELIMINARIES time range. The protocol is efficient, backward compatible, and surprisingly, currently deployed SSL/TLS servers can act as A. Freshness in the Bitcoin Blockchain reference time sources. The protocol has many applications and can be used for detecting various attacks against the Bitcoin Bitcoin is an open cryptocurrency and transaction system.