Crypto boffins propose replacing certification authorities with … Bitcoin?


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Whatever your opinion of Bitcoin, it does stand as a high-quality intellectual achievement. Now, a group of researchers from Johns Hopkins are suggesting its cryptographic implementation could help solve the “certificate problem” for ordinary users.

Apart from whether or not they might be universally compromised by the spooks, a problem with Public Key Infrastructure – PKI – certificates is that they depend on users’ trust of the certification authority (CA) that sits at the top of the trust hierarchy.

As we know, however, from incidents such as the DigiNotar hack, any loss of trust is fatal to a CA. Bitcoin did away with centralised trust in favour of its own cryptographic model, relying instead on a distributed transaction ledger.

In this paper, published at the International Association for Cryptologic Research, researchers Christina Garman, Matthew Green and Ian Miers of John Hopkins University’s Department of Computer Science, propose a similar model, in which anonymous credentials could exist without a centralised CA acting as trusted issuer.

Their idea is that the distributed, public, append-only ledger model used by Bitcoin could be used “by individual nodes, to make assertions about identity in a fully anonymous fashion” – while doing away with CAs as a single point of failure.

“Using this decentralised ledger and standard cryptographic primitives, we propose and provide a proof of security for a basic anonymous credential system that allows users to make flexible identity assertions with strong privacy guarantees,” they write.

Key components of the system are:

  • A Decentralised Direct Anonymous Attestation (dDAA) – the bit that gets rid of the CA.
  • Anonymous resource management in ad hoc networks – using the dDAA technique to prevent impersonation in peer-to-peer networks.
  • Credential auditability – in the same way as the Bitcoin blockchain is auditable because it’s public, the researchers believe, the scheme offers a way to guard against people faking their certificates.

While the researchers present an implementation, they note that this work – still seriously pre-Alpha – needs further development in the security of the transaction ledger, and in the efficiency of the algorithms. ®

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