dirmngr

dirmngr is a daemon that manages certificates and certificate revocation lists (CRLs) for the GNU Privacy Guard (GnuPG). It is a component of GnuPG that operates in the background, providing services to other GnuPG applications. Its primary role is to handle the retrieval and storage of certificate information, as well as the verification of certificate validity.

The dirmngr daemon interacts with certificate directories, which are repositories of public keys and certificate revocation information. It can fetch this information from various sources, including LDAP servers and local files. When a GnuPG application needs to verify a certificate, it can query dirmngr for the relevant CRL or certificate data. This offloads the network communication and caching of this data from individual GnuPG tools, improving efficiency.

Key functions of dirmngr include fetching and caching CRLs, which are lists of certificates that have been revoked by their issuing authority. It also manages public keys, making them readily available for encryption and signature verification. By maintaining local copies of this information, dirmngr can significantly speed up operations that involve checking the validity of certificates.

dirmngr is typically started automatically when needed by other GnuPG components. It listens for requests on a specific network socket. Users generally do not interact with dirmngr directly; its operations are managed by the GnuPG suite as a whole. The daemon plays a crucial role in ensuring the security and reliability of GnuPG's certificate management infrastructure.