CommitCoin: Carbon Dating Commitments with Bitcoin

Abstract. In the standard definition of a commitment scheme, the sender commits to a message and immediately sends the commitment to the recipient interested in it. However the sender may not always know at the time of commitment who will become interested in verifying it. Further, when the interested party does emerge, it could be critical to establish when the commitment was made. Employing a proof of work protocol at commitment time will later allow anyone to “carbon date ” when the commitment was made, approximately, without trusting any external parties. We present CommitCoin, an instantiation of this approach that harnesses the existing processing power of the Bitcoin peer-to-peer network; a network used to mint and trade digital cash. 1 Introductory Remarks Consider the scenario where Alice makes an important discovery. It is important to her that she receives recognition for her breakthrough, however she would also like to keep it a secret until she can establish a suitable infrastructure for monetizing it. By forgoing publication of her discovery, she risks Bob independently making the same discovery and publicizing it as his own. Folklore suggests that Alice might mail herself a copy of her discovery and leave the letter sealed, with the postal service’s timestamp intact, for a later resolution time. If Bob later claims the same discovery, th

Techniques to Audit and Certify the Long Term Integrity of Digital Archives

A large portion of the government, business, cultural, and scientific digital data being created today needs to be archived and preserved for future use of periods ranging from a few years to decades and sometimes centuries. A fundamental requirement for a long term archive is to set up mechanisms that will ensure the authenticity of the holdings of the archive. In this paper, we develop a new methodology to address the integrity of long term archives using rigorous cryptographic techniques. Our approach involves the generation of a small-size integrity token for each digital object to be archived, and some cryptographic summary information based on all the objects handled within a dynamic time period. We present a framework that enables the continuous auditing of the holdings of the archive, as well as auditing upon access, depending on the policy set by the archive. Moreover, an independent auditor will be able to verify the integrity of every version of an archived digital object as well as link the current version to the original form of the object when it was ingested into the archive. Using this approach, a prototype system called ACE (Auditing Control Environment) has been built and tested. ACE is scalable and cost effective, and is completely independent of the archive's underlying architecture

ACE: A Novel Software Platform to Ensure the Integrity of Long Term Archives

We develop a new methodology to address the integrity of long term archives using rigorous cryptographic techniques. A prototype system called ACE (Auditing Control Environment) was designed and developed based on this methodology. ACE creates a small-size integrity token for each digital object and some cryptographic summary information based on all the objects handled within a dynamic time period. ACE continuously audits the contents of the various objects according to the policy set by the archive, and provides mechanisms for an independent third-party auditor to certify the integrity of any object. In fact, our approach will allow an independent auditor to verify the integrity of every version of an archived digital object as well as link the current version to the original form of the object when it was ingested into the archive. We show that ACE is very cost effective and scalable while making no assumptions about the archive architecture. We include in this paper some preliminary results on the validation and performance of ACE on a large image collection

Short-lived signatures

A short-lived signature is a digital signature with one distinguishing feature: with the passage of time, the validity of the signature dissipates to the point where valid signatures are no longer distinguishable from simulated forgeries (but the signing key remains secure and reusable). This dissipation happens "naturally" after signing a message and does not require further involvement from the signer, verifi�er, or a third party. This thesis introduces several constructions built from sigma protocols and proof of work algorithms and a framework by which to evaluate future constructions. We also describe some applications of short-lived signatures and proofs in the domains of secure messaging and voting