At 11:26 AM +0200 8/21/06, Roman Meisl wrote:
Hello,
I've got a question regarding the computing of message hashes. In
chapter 3.7 is listed a formal notation for that algorithm:
body-hash = hash-alg(canon_body)
header-hash = hash-alg(canon_header || DKIM-SIG)
signature = sig-alg(header-hash, key)
I'm not quite sure, what "||" means. I assume it means concatenation
of the two strings. Is that right?
Yes. That is standard terminology in security documents.
Then it would perhaps be better to write
header-hash = hash-alg(canon_header + DKIM-SIG)
or
header-hash = hash-alg(concat(canon_header,DKIM-SIG))
in the second line or at least to mention concatenation explicitly in the
text.
The first could be confusing because "+" normally indicates numeric
addition. The second could also be used, but the action of
concatenation doesn't have be a function.
It would be easiest if the document just said "|| indicates string
concatenation".
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