SHA-1 Broken

From Bruce Schneier’s web log: SHA-1 has been broken. In simple terms, a Hash algorithm takes a document and generates a fingerprint for it. If the document changes, so should the fingerprint. See here for a more more detailed explanation.

Hashes are an important part of any Digital Signature scheme, and SHA-1 is one of the more popular (and until now well-respected) Hash algorithms. Any flaw found in the hashing algorithm is a serious problem for any ELN system that uses Digital Signatures to prove a record has not been changed. As Jon Callas, PGP’s CTO, puts it: ‘It’s time to walk, but not run, to the fire exits. You don’t see smoke, but the fire alarms have gone off.’

So this isn’t a crisis – if you were using digital signatures yesterday, they haven’t suddenly become worthless today. But it is a reminder that nothing lasts forever, especially in Cryptography. Flaws are found in algorithms, computers get faster, and soon it costs a mere $1m to forge the Digital Signature on the document that proves you have the rights to a Blockbuster drug. Picking a “better” algorithm or longer key isn’t going to help – erosion of Cryptographic tools is a fact of life.

Any Evidence system needs to have a series of controls and capabilities to show that a document has been unaltered. Digital Signatures are one of the tools you would use in such a system (we use them in our PatentSafe product) but they shouldn’t be the only thing you rely on. Indeed PatentSafe has a whole series of checks & balances in it and if you run the system properly, even if it turned out the signature algorithm was worthless, you’d still be able to use your records in court.

Unfortunately there are some vendors who are relying on Cryptography alone to prove authenticity. Listening to their marketing, they’re treating the technology as a silver bullet – “Buy this magic, and all your concerns are over”. This has always made me intensely uncomfortable, especially given the timescales that our customers expect to be able to use the records they put into our systems. Fortunately given the level of concern over Electronic Records for patents, few customers have actually implemented such systems – the laggards have been proven correct!

It is possible to do perfectly safe, effective, Electronic Records systems for Patent Evidence Creation and Preservation. Unfortunately, it is a lot harder than just implementing some Cryptographic magic, as the demise of SHA-1 shows. My problem is that it is much easier (and more seductive) to talk about apparently sexy technology rather than the real (but less exciting) issues around good electronic records systems 🙁

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