RE: How to implement the best practice "cache resources"

Isn't the Etag some form of hash already?

Kai


 

> -----Original Message-----
> From: Jo Rabin [mailto:jo@linguafranca.org] 
> Sent: Monday, January 25, 2010 2:53 PM
> To: Rotan Hanrahan
> Cc: Tom Hume; JOSE MANUEL CANTERA FONSECA; Mobile Web Best 
> Practices Working Group WG
> Subject: Re: How to implement the best practice "cache resources"
> 
> I thought you'd do this same way as you would an ETag. But 
> the BP does specify a hash of the resource content, rather 
> than something made from the last modified date, or 
> something. So perhaps the BP is overly prescriptive about this.
> 
> Jo
> 
> On 24/01/2010 22:08, Rotan Hanrahan wrote:
> > That's an interesting question. On seeing that BP for the 
> first time I assumed the fingerprint would be derived from 
> the metadata (mainly the HTTP headers). Certainly one could 
> hash these to facilitate an associative lookup. The question, 
> as posed, raises another possibility, and that is a digital 
> signature of the entire response. Headers and payload. So now 
> I too would like to get some clarity from the proposers.
> >  
> > As for MD5, whether used to hash only (a subset of) the 
> headers or the entire response, there is always the 
> possibility of "hash clash". Despite this, MD5 is still 
> useful as a checksum, though I have my doubts about using it 
> as the sole means of key generation for a resource cache.
> >  
> > If you want to consider an alternative, SHA-2 is worth a 
> look. I get the impression that this is going to take over 
> from MD5 in the near future.
> >  
> > Assuming the security of the hashing is not significant, 
> the focus might turn to the processing efficiency. Maybe some 
> cryptographers reading this might care to comment.
> >  
> > Finally, if you are interested in some open source crypto 
> resources, I recommend you take a look at Bouncy Castle. ( 
> www.bouncycastle.org )
> >  
> > ---Rotan.
> > 
> > ________________________________
> > 
> > From: public-bpwg-request@w3.org on behalf of Tom Hume
> > Sent: Sun 24/01/2010 13:35
> > To: JOSE MANUEL CANTERA FONSECA
> > Cc: Mobile Web Best Practices Working Group WG
> > Subject: Re: How to implement the best practice "cache resources"
> > 
> > 
> > 
> > Would MD5 be a good means of doing this?
> > 
> > 2010/1/21 JOSE MANUEL CANTERA FONSECA <jmcf@tid.es>:
> >> Hi all,
> >>
> >>
> >>
> >> I was trying to find a recommended open source library to 
> calculate a hash
> >> of a resource in accordance with the "cache resources by 
> fingerprinting" bes
> >> practice. any advice, specially from the people who 
> proposed this BP would
> >> be welcome
> >>
> >>
> >>
> >> thank you
> >>
> >>
> >>
> >> best r.
> > 
> > 
> > 
> > --
> > Future Platforms: hungry and foolish since 2000
> > work: Tom.Hume@futureplatforms.com play: tomhume.org
> > 
> > 
> > 
> > 
> 
>

Received on Monday, 25 January 2010 13:59:00 UTC