7.5 Blinding in Proxied Federation

While some proxy structures — typically those that exist primarily to simplify integration — may not offer additional subscriber privacy protection, others offer varying levels of privacy to the subscriber through a range of blinding technologies. Privacy policies may dictate the appropriate use of subscriber attributes and authentication transaction data (e.g., identities of the ultimate IdP and RP) by the IdP, RP, and the federation proxy.

Blinding can also increase the effectiveness of these policies by making the data more difficult to obtain. A proxy-based system has three parties, and the proxy can be used to hide information from one or more of the parties, including itself. In a double-blind proxy, the IdP and RP do not know each other’s identities, and their relationship is only with the proxy. In a triple-blind proxy, the proxy does not have insight into the data being passed through it. As the level of blinding increases, the technical and operational implementation complexity may also increase. Since proxies need to map transactions to the appropriate parties on either side and manage the cryptographic keys for all parties in the transaction, fully triple-blind proxies are very difficult to implement in practice.

Even with the use of blinding technologies, a blinded party may still infer protected subscriber information through released attribute data or metadata (e.g., by analyzing timestamps, attribute bundle sizes, or attribute signer information). The IdP could consider additional privacy-enhancing approaches to reduce the risk of revealing identifying information about the entities participating in the federation.

Table 5 shows a spectrum of blinding implementations used in proxied federation. This table is intended to be illustrative and is neither comprehensive nor technology-specific.

Table 5. Proxy characteristics

1. Panoramica

1.1 Riferimenti

1.2 Requisiti identificati

1.3 Regolamentazioni correlate

2. Requisiti identificati

3. Regolamentazioni correlate

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