Protecting security in cloud and distributed environments

Abstract

Encryption helps to ensure that information within a session is not compromised. Authentication and access control measures ensure legitimate and appropriate access to information, and prevent inappropriate access to such resources. While encryption, authentication and access control each has its own responsibility in securing a communication session, a combination of these three mechanisms can provide much better protection for information.

This thesis addresses encryption, authentication and access control related problems in cloud and distributed environments, since these problems are very common in modern organization environment. The first one is a User-friendly Location-free Encryption System for Mobile Users (UFLE). It is an encryption and authentication system which provides maximum security to sensitive data in distributed environment: corporate, home and outdoors scenarios, but requires minimum user effort (i.e. no biometric entry, or possession of cryptographic tokens) to access the data. It makes users securely and easily access data any time and any place, as well as avoids data breach due to stolen/lost laptops and USB flash. The multi-factor authentication protocol provided in this scheme is also applicable to cloud storage.

The second one is a Simple Privacy-Preserving Identity-Management for Cloud Environment (SPICE). It is the first digital identity management system that can satisfy “unlinkability”and “delegatable authentication” in addition to other desirable properties in cloud environment. Unlinkability ensures that none of the cloud service providers (CSPs), even if they collude, can link the transactions of the same user. On the other hand, delegatable authentication is unique to the cloud platform, in which several CSPs may join together to provide a packaged service, with one of them being the source provider which interacts with the clients and performs authentication, while the others are receiving CSPs which will be transparent to the clients. The authentication should be delegatable such that the receiving CSP can authenticate a user without a direct communication with either the user or the registrar, and without fully trusting the source CSP.

The third one addresses re-encryption based access control issue in cloud and distributed storage. We propose the first non-transferable proxy re-encryption scheme [16] which successfully achieves the non-transferable property. Proxy re-encryption allows a third-party (the proxy) to re-encrypt a ciphertext which has been encrypted for one party without seeing the underlying plaintext so that it can be decrypted by another. A proxy re-encryption scheme is said to be non-transferable if the proxy and a set of colluding delegatees cannot re-delegate decryption rights to other parties. The scheme can be utilized for a content owner to delegate content decryption rights to users in the untrusted cloud storage. The advantages of using such scheme are: decryption keys are managed by the content owner, and plaintext is always hidden from cloud provider.