(Short Paper) Towards More Reliable Bitcoin Timestamps
This addresses a security vulnerability in Bitcoin's timestamping for users relying on its decentralized trust, though it is an incremental improvement to an existing protocol.
The paper tackles the problem of unreliable timestamps in Bitcoin's blockchain, which undermines its use as a secure timestamping service, by introducing a mechanism that provides evidence for block creation within specific time ranges, leveraging existing SSL/TLS servers as reference sources.
Bitcoin provides freshness properties by forming a blockchain where each block is associated with its timestamp and the previous block. Due to these properties, the Bitcoin protocol is being used as a decentralized, trusted, and secure timestamping service. Although Bitcoin participants which create new blocks cannot modify their order, they can manipulate timestamps almost undetected. This undermines the Bitcoin protocol as a reliable timestamping service. In particular, a newcomer that synchronizes the entire blockchain has a little guarantee about timestamps of all blocks. In this paper, we present a simple yet powerful mechanism that increases the reliability of Bitcoin timestamps. Our protocol can provide evidence that a block was created within a certain time range. The protocol is efficient, backward compatible, and surprisingly, currently deployed SSL/TLS servers can act as reference time sources. The protocol has many applications and can be used for detecting various attacks against the Bitcoin protocol.