Detaching signature from signed object

Matthew Richardson matthew-l at
Mon Jun 21 11:04:37 CEST 2021

On Sun, 20 Jun 2021 18:22:53 +0000, ?????? ?????? via Gnupg-users wrote:-

>12021/04/10 05:36.72 ?????, Matthew Richardson via Gnupg-users <gnupg-users at> ??????:
>> Is there any way in GnuPG to detach (or extract) a signature from a signed
>> object?  For example, a signed object is created with:-
>> >gpg --armor --output signedfile.asc --sign inputfile.txt
>> where what is wanted is a detached signature which would verify against
>> inputfile.txt.
>> This feature is in PGP 2:-
>> >pgp -sa inputfile.txt -o signedfile.asc
>> >pgp -b signedfile.asc -o verified.txt
>> which also produces verified.pgp as the detached signature.  The feature is
>> described (briefly) in the PGP 2 documentation thus:-
>> >To detach a signature certificate from a signed message:
>> >     pgp -b ciphertextfile
>> The reason for asking is that I operate a service [1], which currently used
>> PGP 2, and which would benefit from more recent crypto, but which also uses
>> "pgp -b" extensively.
>> Best wishes,
>> Matthew
>> [1]
>I believe you're looking for the -sb option, which creates a detached signature.

Unless I have misunderstood (and please correct me if I have), "-sb" SIGNS
producing a detached signature, whereas I am wanting to detach an EXISTING
signature from an already signed object.

Best wishes,

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