Chaining up Time: Bitcoin and Long-Term Validity of PKI Timestamp Tokens

Abstract

Timestamping is a technique used to prove the existence of certain digital data prior to a specific point in time. With the digitalization process of the economy, timestamping has become an important technique to ensure the integrity of digital data for a long time period. The most popular timestamping scheme and service, based on Public Key Infrastructure (PKI) technology, still has some shortcomings in terms of long-term validation. Since 2009 Bitcoin has been creating a thermodynamically immutable register. That register, aka blockchain, can be used as well to prove the existence of certain digital data prior to a specific point in time, and without any predefined limitation for long-term validation. This paper describes the aspects that make timestamping on the Bitcoin blockchain complementary to commonly widespread Time Stamping Authority services, which are standardized and legally recognized; and proposes some technically viable solutions to integrate the two timestamping schemes.