I tried to update my client using the following:

sudo curl -fsSL https://boinc.berkeley.edu/dl/linux/stable/bookworm/boinc.gpg | sudo gpg --dearmor -o /etc/apt/keyrings/boinc.gpg
sudo echo deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/boinc.gpg] https://boinc.berkeley.edu/dl/linux/stable/bookworm bookworm main | sudo tee /etc/apt/sources.list.d/boinc.list > /dev/null
sudo apt update
sudo apt install boinc-client boinc-manager

However when I get tried the steps I get a GPG error.

It says the public key is not available and is 'not signed'.

When I tried to add the repository using the Synaptic Package Manager I get the same error.

Any ideas what is causing this? I use Debian but am far from an expert.

Thanks

Here is more detailed info:

GPG error: https:/boinc.berkeley.edu/dl/linux/stable/bookworm bookwork InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40254C9B29853EA6 The repository 'https://boinc.berkeley.edu/dl/linux/stable/bookworm bookworm InRelease' is not signed.