Improved Fault Templates of Boolean Circuits in Cryptosystems can Break Threshold Implementations

Fault Template Analysis (FTA) has been shown as a powerful tool for attacking cryptosystems and exposing vulnerabilities which were previously not reported in existing literature. Fault templates can be utilized for attacking block ciphers in middle rounds which were known prior to be resistant against fault attacks. In this paper we revisit the potent of fault templates and show a more systematic methodology to develop fault templates of Boolean circuits using a well known concept in design verification, namely positive Davio\u27s decomposition. We show that the improved FTAs, called FTA2.0, can be used to fault analyze block ciphers in the middle rounds using as few as two bit-flip faults. Further, it can be used to attack TI-implemented block ciphers by considering a Double Bit Upset (DBU) fault in a target share bit. The attack shows that varying the latency of the fault the adversary can obtain unmasked bits and can recover the secret key

Embed-Augment-Recover: Function Private Predicate Encryption from Minimal Assumptions in the Public-Key Setting

We present a new class of public-key predicate encryption schemes that are provably function private in the standard model under well-known cryptographic assumptions, and assume predicate distributions satisfying realistic min-entropy requirements. More concretely, we present public-key constructions for identity-based encryption (IBE) and inner-product encryption (IPE) that are computationally function private in the standard model under a family of weaker variants of the DLIN assumption. Existing function private constructions in the public-key setting impose highly stringent requirements on the min-entropy of predicate distributions, thereby limiting their applicability in the context of real-world predicates. For example, the statistically function private constructions of Boneh, Raghunathan and Segev (CRYPTO\u2713 and ASIACRYPT\u2713) are inherently restricted to predicate distributions with min-entropy roughly proportional to $\lambda$, where $\lambda$ is the security parameter. Our constructions allow relaxing this min-entropy requirement to $\omega(\log\lambda)$, while achieving a computational notion of function privacy against probabilistic polynomial-time adversaries, which suffices for most real-world applications. Our constructions also avoid the need for strong assumptions such as indistinguishability obfuscation

An Improved DCM-based Tunable True Random Number Generator for Xilinx FPGA

True Random Number Generators (TRNGs) play a very important role in modern cryptographic systems. Field Programmable Gate Arrays (FPGAs) form an ideal platform for hardware implementations of many of these security algorithms. In this paper we present a highly efficient and tunable TRNG based on the principle of Beat Frequency Detection (BFD), specifically for Xilinx FPGA based applications. The main advantages of the proposed TRNG are its on-the-fly tunability through Dynamic Partial Reconfiguration (DPR) to improve randomness qualities. We describe the mathematical model of the TRNG operations, and experimental results for the circuit implemented on a Xilinx Virtex-V FPGA. The proposed TRNG has low hardware footprint and in-built bias elimination capabilities. The random bitstreams generated from it passes all tests in the NIST statistical testsuite

New Lower Bounds on Predicate Entropy for Function Private Public-Key Predicate Encryption

We present function private public-key predicate encryption schemes from standard cryptographic assumptions, that achieve new lower bounds on the min-entropy of underlying predicate distributions. Existing function private predicate encryption constructions in the public-key setting can be divided into two broad categories. The first category of constructions are based on standard assumptions, but impose highly stringent requirements on the min-entropy of predicate distributions, thereby limiting their applicability in the context of real-world predicates. For example, the statistically function private constructions of Boneh, Raghunathan and Segev (CRYPTO\u2713 and ASIACRYPT\u2713) are inherently restricted to predicate distributions with min-entropy roughly proportional to the security parameter $\lambda$. The second category of constructions mandate more relaxed min-entropy requirements, but are either based on non-standard assumptions (such as indistinguishability obfuscation) or are secure in the generic group model. In this paper, we affirmatively bridge the gap between these categories by presenting new public-key constructions for identity-based encryption, hidden-vector encryption, and subspace-membership encryption~(a generalization of inner-product encryption) that are both data and function private under variants of the well-known DBDH, DLIN and matrix DDH assumptions, while relaxing the min-entropy requirement on the predicate distributions to $\omega(\log\lambda)$. In summary, we establish that the minimum predicate entropy necessary for any meaningful notion of function privacy in the public-key setting, is in fact, sufficient, for a fairly rich class of predicates