The Java Cryptography Architecture, JCA in short, was created to allow JCA-compliant cryptography providers to be plugged into a JCA-aware application at run time. This configurable feature makes JCA widely used and assures its success. However, the public key cryptographic service interfaces defined by JCA are based on the conventional public key cryptography, which is a single-sender-singlereceiver model, and does not accommodate the group-based public key cryptography well. Especially, it does not support the threshold cryptography (TC), an important type of group-based public key cryptography, which has been shown to be a useful tool to enhance system security. As a step towards the systematic application of group-based public key cryptography, this article proposes an extension to the JCA framework to integrate threshold cryptography. Under this extension, various TC providers implementing different TC primitives can be plugged into a security application at run-time. This extens...