Search

The promise of identity-based systems is that they maintain the functionality of public key cryptography while eliminating the need for public key certificates. The first efficient identity-based encryption (IBE) scheme was proposed by Boneh and Franklin in 2001; variations have been proposed by many researchers since then. However, a common drawback is the requirement for a private key generator (PKG) that uses its own master private key to compute private keys for end users. Thus, the PKG can potentially decrypt all ciphertext in the environment (regardless of who the intended recipient is), which can have undesirable privacy implications. This has led to limited adoption and deployment of IBE technology. There have been numerous proposals to address this situation (which are often characterized as methods to reduce trust in the PKG). These typically involve threshold mechanisms or separation-of-duty architectures, but unfortunately often rely on non-collusion assumptions that cannot be guaranteed in real-world settings. This paper proposes a separation architecture that instantiates several intermediate CAs (ICAs), rather than one (as in previous work). We employ digital credentials (containing a specially-designed attribute based on bilinear maps) as the blind tokens issued by the ICAs, which allows a user to easily obtain multiple layers of pseudonymization prior to interacting with the PKG. As a result, our proposed architecture does not rely on unrealistic non-collusion assumptions and allows a user to reduce the probability of a privacy breach to an arbitrarily small value.

This paper extends previous work to strengthen the enforcement portion of a comprehensive architecture for enforcing privacy when a user needs to submit personal data to an Internet website in order to obtain goods or services. Our extension proposes to use a website's P3P privacy policy (derived in an automated way from its internal XACML access control policy) as a public key to encrypt the user's data using IBE (identity-based encryption) technology. The website will only acquire the corresponding private key to decrypt this data if a trusted 3rd-party auditor (acting as an IBE private key generator) has verified that the P3P policy is an accurate statement of the site's internal privacy practices. We discuss all the components of this model and describe our proof-of-concept implementation which demonstrates that such an architecture is feasible in real-world scenarios.

Effective emergency (such as a hurricane, a building on fire, and so on) response requires accurate, relevant, timely, and location-aware information (e.g., environmental information, health records, and so on). Acquiring information in such critical situations encounters substantial challenges, such as large volume of data processing, unstructured data, privacy, authorized data access, and so forth. Among the issues, access authorization has received little attention. Existing solutions for data authorization either do not scale well or merely consider a Break-the-Glass concept in which a master key is provided to the first responders (FRs) to decrypt the corresponding ciphertext. This may not only enable unauthorized users to access information, but it may also overwhelm FRs by the large volume of accessible data. To jointly address the aforementioned issues, this paper proposes a location-aware authorization scheme that enables FRs to access information provided that they are within a predefined distance from data owners at the time of an emergency. We innovatively integrate attribute-based encryption with broadcast encryption to incorporate dynamic attributes (i.e., location and time) into an access policy. Such attributes act as filters to eliminate data irrelevant to an ongoing emergency. As a result, our scheme provides authorized access to accurate, relevant, timely, and location-aware information. We provide extensive security analysis and performance evaluations to demonstrate the effectiveness of our scheme. The analysis shows that the scheme imposes constant communication and decryption computation overheads. Furthermore, the proposed scheme is proven chosen plain-text attack selectively secure based on m-bilinear Diffie-Hellman exponent assumption. It also addresses the key escrow problem.