On Wed 18/Jun/2025 23:09:30 +0200 internet-drafts wrote:
https://datatracker.ietf.org/doc/html/draft-gondwana-dkim2-modification-alegbra-02
May I note that the text is hard to grok? In particular:
It is a simple program describing ranges of data
to copy from the output to recreate the input.
I guess the output is the modified message while the input is the original,
although reversing would imply removing, not copying. This sounds like the
modifications consist in inserting lines. Not deleting or replacing lines, nor
inserting stuff in the middle of a line. I would concur with that stance, but
I doubt it's what you mean.
The example sounds unreal, as both hops add 500 lines of text.
DKIM2-Delta-Body: i=2; c=1-500; c=520-520
Of course it makes no sense to have changes at i=1 (maybe worth noting it?)
Example - a URL was substituted in the content of the body (complex,
but still easily doable!)
Is that the text of the message before changing?
DKIM2-Delta-Body: i=3;
c=1-500;
b=PGEgaHJlZj0iaHR0cHM6Ly93d3cuZXhhbXBsZS5jb20iPkV4YW1wbGU8L2E+Cg==;
c=501-702
I reckon the final message is at least 1221 lines long. To recreate the
original I first remove lines 501-702; then I remove the line "<a .../a>\n"[*],
but from where? You say it was substituted, but with what? Then I remove lines
1-1000; and then I remove the 19th line (which was c=520-520). Correct?
[*] Shouldn't it be
b=PGEgaHJlZj0iaHR0cHM6Ly93d3cuZXhhbXBsZS5jb20iPkV4YW1wbGU8L2E+DQo=?
Finally, the most disconcerting point is:
z=y MUST be the only source; changes are not reversible via this mechanism
Didn't we say it's not DKIM2 if it's not reversible? In any case what are z
and y?
Best
Ale
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