errore signature verification in testing

[Piviul <piviul@riminilug.it>]

Ciao a tutti, è qualche giorno che ricevo questo errore durante l'update:

> $ sudo apt update
> Get:1 http://deb.debian.org/debian bullseye InRelease [142 kB]
> Err:1 http://deb.debian.org/debian bullseye InRelease
>   Unknown error executing apt-key
> Reading package lists... Done
> Building dependency tree... Done
> Reading state information... Done
> All packages are up to date.
> W: An error occurred during the signature verification. The repository 
> is not updated and the previous index files will be used. GPG error: 
> http://deb.debian.org/debian bullseye InRelease: Unknown error 
> executing apt-key
> W: Failed to fetch 
> http://deb.debian.org/debian/dists/bullseye/InRelease ; Unknown error 
> executing apt-key
> W: Some index files failed to download. They have been ignored, or old 
> ones used instead.
Avete idea di come si possa risolvere?

Grazie

Piviul