A keystore is a type of database that holds certificates.
The following examples represent the most common forms of keystores:
- File that uses the Java-specific Java KeyStore (JKS) format
- File that uses the standard PKCS #12 format
- Collection of files that holds certificates and private keys, typically in PEM or DER format
- Hardware security module (HSM) that makes the certificate information available through an interface like PKCS #11
The server supports file-based keystores by using the JKS and PKCS #12 formats and by using hardware security modules that are accessible through PKCS #11. The server does not currently support a keystore format that consists of individual certificate and private key files. To import these files into a JKS or PKCS #12 keystore, use the manage-certificates tool.
A keystore also represents a collection of entries, each of which is identified by a name that an alias calls. Keystores can have the following entry types:
- Private key entries
- Contain a certificate chain and a private key. When a server accepts a TLS-based connection, it uses a private key entry to obtain the certificate chain that it presents to the client. The server can also use the private key from the same entry to process its key agreement. Similarly, a client uses a private key entry when presenting its own certificate chain to a server.
- Trusted certificate entries
- Contain a single certificate without a private key. As the name implies, a trusted certificate entry is intended primarily for use when determining whether to trust a certificate chain that is presented during TLS negotiation.
- Secret key entries
- Contain a secret key only, without an associated certificate. These types of entries are not used for TLS processing. Instead, they hold symmetric encryption keys or other types of secrets.
A password, sometimes called a PIN, protects the contents of a keystore. In some cases, like with JKS keystores, some content might be accessible without a password, and a password might be required only when trying to access private keys or secret keys. In other cases, like with PKCS #12 keystores, you might need a password for any interaction with the keystore.
Additional passwords can further protect private keys. This approach is often the same as with the keystore password, but the password can be different. This tactic is useful when a single keystore is shared for multiple purposes, for example, and when merely having access to the keystore does not guarantee access to all of the data that it contains.
A truststore is another name for a keystore that is intended primarily for use when determining whether to trust a certificate chain that has been presented. Truststores generally contain primarily trusted certificate entries, but that case is not required.
Java runtime environments typically include a default truststore, often jre/lib/security/cacerts or lib/security/cacerts, that is prepopulated with several widely trusted certification authority certificates. When presented with a certificate that one of these authorities has signed, the default truststore can allow the certificate to be trusted without any additional configuration. When presented with a self-signed certificate, or when presented with a certificate that is signed by an issuer not in the default truststore, such as a private corporate certification authority, a separate truststore is required.