Examples include service authentication for a principal. A request to access a first service of a plurality of services of a network may be received from a principal by an identity intermediary. An identifier of the first service may be stored at the identity intermediary, and an unsigned credential of the principal and a principal identifier may be transferred from the identity intermediary to a credential provider. The principal identifier and the credential signed by the credential provider may be received, and the signed credential may be transmitted to the first service for authentication.