There has been a notable surge of research on leakage-resilient authenticated encryption (AE) schemes, in the bounded as well as the unbounded leakage model. The latter has garnered significant attention due to its detailed and practical orientation. Designers have commonly utilized (tweakable) block ciphers, exemplified by the TEDT scheme, achieving $\mathcal{O}(n-\log(n^2))$-bit integrity under leakage and comparable AE security in the black-box setting. However, the privacy of TEDT was limited by $n/2$-bits under leakage; TEDT2 sought to overcome these limitations by achieving improved security with $\mathcal{O}(n-\log n)$-bit integrity and privacy under leakage.

This work introduces FEDT, an efficient leakage-resilient authenticated encryption (AE) scheme based on fork-cipher. Compared to the state-of-the-art schemes TEDT and TEDT2, which process messages with a rate of $1/2$ block per primitive call for encryption and one for authentication, FEDT doubles their rates at the price of a different primitive. FEDT employs a more parallelizable tree-based encryption compared to its predecessors while maintaining $\mathcal{O}(n-\log n)$-bit security for both privacy and integrity under leakage. FEDT prioritizes high throughput at the cost of increased latency. For settings where latency is important, we propose FEDT*, which combines the authentication part of FEDT with a CTR-based encryption. FEDT* offers security equivalent to FEDT while increasing the encryption rate of $4/3$ and reducing the latency.

In this paper, we aim to explore the design of low-latency authenticated encryption schemes particularly for memory encryption, with a focus on the temporal uniqueness property. To achieve this, we present the low-latency Pseudo-Random Function (PRF) called Twinkle with an output up to 1152 bits. Leveraging only one block of Twinkle, we developed Twinkle-AE, a specialized authenticated encryption scheme with six variants covering different cache line sizes and security requirements. We also propose Twinkle-PA, a pointer authentication algorithm, which takes a 64-bit pointer and 64-bit context as input and outputs a tag of 1 to 32 bits.

We conducted thorough security evaluations of both the PRFs and these schemes, examining their robustness against various common attacks. The results of our cryptanalysis indicate that these designs successfully achieve their targeted security objectives.

Hardware implementations using the FreePDK45nm library show that Twinkle-AE achieves an encryption and authentication latency of 3.83 ns for a cache line. In comparison, AES-CTR with WC-MAC scheme and Ascon-128a achieve latencies of 9.78 ns and 27.30 ns, respectively. Moreover, Twinkle-AE is also most area-effective for the 1024-bit cache line. For the pointer authentication scheme Twinkle-PA, the latency is 2.04 ns, while QARMA-64-sigma0 has a latency of 5.57 ns.

The size of the authentication tag represents a significant overhead for applications that are limited by bandwidth or memory. Hence, some authenticated encryption designs have a smaller tag than the required privacy level, which was also suggested by the NIST lightweight cryptography standardization project. In the ToSC 2022, two papers have raised questions about the IND-CCA security of AEAD schemes in this situation. These papers show that (a) online AE cannot provide IND-CCA security beyond the tag length, and (b) it is possible to have IND-CCA security beyond the tag length in a restricted Encode-then-Encipher framework. In this paper, we address some of the remaining gaps in this area. Our main result is to show that, for a fixed stretch, Pseudo-Random Injection security implies IND-CCA security as long as the minimum ciphertext size is at least as large as the required IND-CCA security level. We also show that this bound is tight and that any AEAD scheme that allows empty plaintexts with a fixed stretch cannot achieve IND-CCA security beyond the tag length. Next, we look at the weaker notion of MRAE security, and show that two-pass schemes that achieve MRAE security do not achieve IND-CCA security beyond the tag size. This includes SIV and rugged PRPs.

Verifiable encryption (VE) is a protocol where one can provide assurance that an encrypted plaintext satisfies certain properties, or relations. It is an important building block in cryptography with many useful applications, such as key escrow, group signatures, optimistic fair exchange, and others. However, the majority of previous VE schemes are restricted to instantiation with specific public-key encryption schemes or relations. In this work, we propose a novel framework that realizes VE protocols using zero-knowledge proof systems based on the MPC-in-the-head paradigm (Ishai et al. STOC 2007). Our generic compiler can turn a large class of zero-knowledge proofs into secure VE protocols for any secure public-key encryption scheme with the undeniability property, a notion that essentially guarantees binding of encryption when used as a commitment scheme. Our framework is versatile: because the circuit proven by the MPC-in-the-head prover is decoupled from a complex encryption function, the work of the prover is focused on proving the encrypted data satisfies the relation, not the proof of plaintext knowledge. Hence, our approach allows for instantiation with various combinations of properties about the encrypted data and encryption functions. We then consider concrete applications, to demonstrate the efficiency of our framework, by first giving a new approach and implementation to verifiably encrypt discrete logarithms in any prime order group more efficiently than was previously known. Then we give the first practical verifiable encryption scheme for AES keys with post-quantum security, along with an implementation and benchmarks.