By default, when verifying a signed file or a file with a detached signature, which keyring is used to search for public keys?

~/.gnupg/trustdb.gpg is the trust database, which stores information about the trust level of keys, not the public keys themselves.

~/.gnupg/secring.gpg (or private-keys-v1.d in newer GnuPG) stores private keys, which are used for signing or decrypting, not for verifying other people's signatures.

When performing signature verification, GPG often consults the ~/.gnupg/trustedkeys.gpg file by default to search for the public key of the signer. This keyring is specifically intended for storing public keys that are considered trusted for verifying signatures.

~/.gnupg/pubring.gpg is the main public keyring containing all imported public keys, but in many verification contexts, GPG prioritizes trustedkeys.gpg as the default location for keys explicitly relied upon for signature validation.