Currently, there is one database per JDK installation. See JAR Files and Digital Signatures for more information. Identities are real-world entities such as people, companies or organizations that have a public key associated with them. An identity may also have associated with it one or more certificates authenticating its public key. A certificate is a digitally signed statement from one entity, saying that the public key of some other entity has a particular value.
Signers are entities that have private keys in addition to corresponding public keys.
Private keys differ from public keys in that they can be used for signing. Prior to signing any files, a signer must have a public and private key pair associated with it, and at least one certificate authenticating its public key. In javakey , you can either import existing keys or generate new ones for association with identities and signers. Similarly, you can either import existing certificates or generate new ones. Subsequent javakey commands must use this same username to refer to the entity.