Which technology uses realms to facilitate trust in identity information across organizations?

WS-Federation is designed to enable the sharing of identity information across different organizations or domains by establishing a trust relationship, often referred to as a "realm." In this context, a realm represents a domain of identity credential management. By using WS-Federation, different federated systems can verify identities and share attributes securely without needing to manage multiple credentials for different services.

This technology employs a federated identity model which allows users to authenticate once and gain access to services across various organizations while maintaining a sense of trust that the identity information is accurate and protected. WS-Federation supports scenarios where business partners or organizations need to collaborate by establishing a framework that allows for secure interaction while taking into account the relationships and trust levels between the various parties involved.

In contrast, OAuth primarily facilitates authorization rather than identity federation and does not inherently use realms to manage trust across organizations. Kerberos is focused on providing secure authentication within a single domain rather than across multiple organizations, and CAS (Central Authentication Service) is another form of single sign-on but does not emphasize realms in the same way that WS-Federation does for establishing cross-domain trust in identity information.