Difference between clearsign and detached signatures?
kloecker at kde.org
Fri Aug 29 20:03:43 CEST 2014
On Thursday 28 August 2014 22:53:52 TJ wrote:
> I've recently been digging deep into the source-code trying to
> understand what the differences are between --clearsign and
> --detach-sign signatures.
The RFC is probably much easier to read than the source code:
> This came about whilst writing code that calls on "gpg --verify" on
> detached signatures; specifically Debian APT archives that contain
> "Release" (plaintext) and "Release.gpg" (detached signature).
> The aim/hope was to combine the plaintext and detached signature into
> the armored clearsign format and thus avoid needing to write one of
> them to the file-system (the other can be supplied via stdin).
> I had thought that the message digest hash (in this case SHA512)
> should be the same since the input data is the same which-ever
> signing method is used. This didn't work as I had expected so I have
> been digging into the source-code to figure out what is different
> between the two signing methods.
In general the message digest hashes will differ. The reason for this is
a different canonicalization of the signed text (provided the detached
signature is a text document signature; if it's a binary document
signature no canonicalization is applied). A main difference is the
stripping of trailing whitespace in the text (which is done for
cleartext signatures but not for text document signature).
For details see
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