Re: Thoughts on CLASS and ROLE attributes in HTML 3 draft

lilley (
Mon, 13 Mar 1995 11:37:46 +0000 (GMT)

Peter Flynn writes:

>[attribution deleted] wrote:

> > This is a one-way hashing algorithm. Will always be 32 base-64 encoded
> > chars long. ie:
> > MD5("foobar") = 3858f62230ac3c915f300c664312c63f

> Where does a user get a standalone base64 binary that will hash a string
> argument so the result can be included?

> > This is to make sure that the referenced document has not changed since
> > the author made the link.

> This obviously refers to some mechanism that I'm not familiar with. Where
> in the referenced doc will the matching string appear? Or is this something
> that a MIME-compliant system generates (by the goddess my MIME knowledge is
> _not_ up to scratch :-)


Do not mix up the use of base64 in MIME with this particular base64 attribute.

In a MIME message, the base64 stuff carries the *content* (encoded to geth
through hostile mail transports).

In the MD5 attribute, the base64 string is *generated from* the content (by the
author of the document), but the reader accessed the content in the normal
way, through a link.

Having got the content, the browser can then compute an MD5 on it and confirm
(because it is the same as the MD5 attribute on the link) that the retrieved
document is the very same one that the document author was looking at.

<p>Here is my <a href="url" MD5("Chris")=3858f62230ac3c915f300c664312c63f>
last will and testament</a>.</p>


Chris Lilley
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