The proliferation of e-services (e.g. e-commerce, e-health, e-government) within the emerging digital Identity Management Systems make Internet an undeniable convenient and powerful tool for users. However in this environment, users are required to manage several digital identities and a great number of personal data. As such, simplification of users' involvement is highly needed while increasing the users' confidence, and guaranteeing security. This paper proposes a low-cost authentication solution which leads to a reduction of users' identities, even across several circles of trust, while maintaining high-level security. This solution is suitable for FC2, a platform dedicated to manage digital identities within circles of trust.