CROO: A universal infrastructure and protocol to detect identity fraud

Identity fraud (IDF) may be defined as unauthorized exploitation of credential information through the use of false identity. We propose CROO, a universal (i.e. generic) infrastructure and protocol to either prevent IDF (by detecting attempts thereof), or limit its consequences (by identifying cases of previously undetected IDF). CROO is a capture resilient one-time password scheme, whereby each user must carry a personal trusted device used to generate one-time passwords (OTPs) verified by online trusted parties. Multiple trusted parties may be used for increased scalability. OTPs can be used regardless of a transaction’s purpose (e.g. user authentication or financial payment), associated credentials, and online or on-site nature; this makes CROO a universal scheme. OTPs are not sent in cleartext; they are used as keys to compute MACs of hashed transaction information, in a manner allowing OTP-verifying parties to confirm that given user credentials (i.e. OTP-keyed MACs) correspond to claimed hashed transaction details. Hashing transaction details increases user privacy. Each OTP is generated from a PIN-encrypted non-verifiable key; this makes users’ devices resilient to off-line PIN-guessing attacks. CROO’s credentials can be formatted as existing user credentials (e.g. credit cards or driver’s licenses)

Kamouflage: loss-resistant password management

We introduce Kamouflage: a new architecture for building theft-resistant password managers. An attacker who steals a laptop or cell phone with a Kamouflage-based password manager is forced to carry out a considerable amount of online work before obtaining any user credentials. We implemented our proposal as a replacement for the built-in Firefox password manager, and provide performance measurements and the results from experiments with large real-world password sets to evaluate the feasibility and effectiveness of our approach. Kamouflage is well suited to become a standard architecture for password managers on mobile devices

On the impacts of mathematical realization over practical security of leakage resilient cryptographic schemes

In real world, in order to transform an abstract and generic cryptographic scheme into actual physical implementation, one usually undergoes two processes: mathematical realization at algorithmic level and physical realization at implementation level. In black-box model (i.e. leakage-free setting), a cryptographic scheme can be mathematically realized without affecting its theoretical security as long as the mathematical components meet the required cryptographic properties. However, up to now, no previous work formally show that whether one can mathematically realize a leakage resilient cryptographic scheme in existent ways without affecting its practical security. Our results give a negative answer to this important question by introducing attacks against several kinds of mathematical realization of a practical leakage resilient cryptographic scheme. To be specific, there may exist a big gap between the theoretical tolerance leakage bits number and the practical tolerance leakage bits number of the same leakage resilient cryptographic scheme if the mathematical components in the mathematical realization are not provably secure in leakage setting

After-the-fact leakage in public-key encryption

What does it mean for an encryption scheme to be leakage-resilient? Prior formulations require that the scheme remains semantically secure even in the presence of leakage, but only considered leakage that occurs before the challenge ciphertext is generated. Although seemingly necessary, this restriction severely limits the usefulness of the resulting notion. In this work we study after-the-fact leakage, namely leakage that the adversary obtains after seeing the challenge ciphertext. We seek a “natural ” and realizable notion of security, which is usable in higher-level protocols and applications. To this end, we formulate entropic leakageresilient PKE. This notion captures the intuition that as long as the entropy of the encrypted message is higher than the amount of leakage, the message still has some (pseudo) entropy left. We show that this notion is realized by the Naor-Segev constructions (using hash proof systems). We demonstrate that entropic leakage-resilience is useful by showing a simple construction that uses it to get semantic security in the presence of after-the-fact leakage, in a model of bounded memory leakage from a split state.