Re: [perpass] Draft charter for a Transparency Working Group

Hi all -

A further suggestion inline. One motivation for my suggesting a change is that I am instinctively uneasy when the word "proof" crops up in this kind of context. I think what we're doing is providing the means to accrue evidence, on the basis of which someone can make an inference as to whether correct log behaviour has been recorded. 

R

On 6 Jan 2014, at 17:02, Ben Laurie wrote:

> On 30 December 2013 15:36, Stephen Kent <kent@bbn.com> wrote:
>> Ben,
>> 
>>> How's this?
>>> 
>>> [1] A cryptographically verifiable log is an append-only log of hashes
>>> of more-or-less anything that can prove its own correctness
>>> cryptographically.
>>> 
>>> For example, from RFC 6962: “The append-only property of each log is
>>> technically achieved using Merkle Trees, which can be used to show
>>> that any particular version of the log is a superset of any particular
>>> previous version. Likewise, Merkle Trees avoid the need to blindly
>>> trust logs: if a log attempts to show different things to different
>>> people, this can be efficiently detected by comparing tree roots and
>>> consistency proofs. Similarly, other misbehaviours of any log (e.g.,
>>> issuing signed timestamps for certificates they then don't log) can be
>>> efficiently detected and proved to the world at large.”
>>> 
>>> See RFC 6962,
>>> http://www.links.org/files/CertificateTransparencyVersion2.1a.pdf
>>> and http://www.links.org/files/RevocationTransparency.pdf for
>>> background.
>>> 
>> Sorry to be so late in responding; holidays ...
> 
> Likewise.
> 
>> The text describing how 6962 uses Merkle trees is good. I think the
>> phrase "prove its own correctness" is way too broad. The example
>> you cite shows how to demonstrate internal consistency for a log,
>> and to enable third parties to verify certain lob properties. That
>> is much narrower than what the term "correctness" implies.
> 
> How about, instead of "can prove its own correctness
> cryptographically", we say "allows efficient verification of
> behaviour"?

"A cryptographically verifiable log is an append-only log of hashes, structured in such a way as to provide efficiently-accessible, cryptographically-supported evidence of correct [log] behaviour". 

That way, you capture the following:

- use of hashing/cryptographic mechanisms to maintain the integrity of the evidence trail
- reference to the relevance of structure (Merkle trees)
- de-coupling of the evidence (signed records) from what it is that the evidence is intended to show (correct behaviour)

Hope this helps - 

Robin

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