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` stores the GnuPG trust database, which records the trust relationships between keys and their owners, not the public keys themselves.

`~/.gnupg/secring.gpg` (or `~/.gnupg/private-keys-v1.d/` in modern GnuPG versions) is where private keys are stored, used for signing or decryption, not for verifying others' signatures.

`~/.gnupg/trustedkeys.gpg` is not the default primary public keyring; while it can be used for specific trusted keys, `pubring.gpg` is the main repository for public keys.

The `~/.gnupg/pubring.gpg` file is the default and primary keyring where GnuPG stores all public keys, which are necessary to authenticate the origin and integrity of signed files or to encrypt data for others.