This command checks the validity and trust of the signature on a disk image or XIP archive. On macOS 10.12 or later, it also tests whether a signed disk image passes a Gatekeeper assessment. On macOS 10.15 and later, this includes testing whether the disk image is notarized. See also: Signing.
If a disk image’s signature is invalid, e.g. because a code signing certificate was revoked, you can remove the signature using DropDMG’s Convert Image/Archive… command.