In this paper we propose Differential Fault Attack (DFA) on two Fully Homomorphic Encryption (FHE) friendly stream ciphers Rasta and$\text{FiLIP}_{\text{DSM}}$. Design criteria of Rasta rely on affine layers and nonlinear layers, whereas$\text{FiLIP}_{\text{DSM}}$relies on permutations and a nonlinear filter function. Here we show that the secret key of these two ciphers can be recovered by injecting only 1 bit fault in the initial state. Our DFA on full round (# rounds$=6$) Rasta with 219 block size requires only one block (i.e., 219 bits) of normal and faulty keystream bits. In the case of our DFA on FiLIP-430 (one instance of$\text{FiLIP}_{\text{DSM}}$), we need 30000 normal and faulty keystream bits.

Abstract With the help of a multi-signature scheme, we can reduce the cost of storage and bandwidth in case of many signers signing the same message. Therefore, multi-signature schemes can be used in bitcoin to reduce the size of a blockchain. In this paper, we propose a lattice-based multi-signature scheme with the following highlighted features. Our lattice-based multi-signature scheme supports signature compression and public key aggregation. The only existing lattice-based multi-signature scheme by Kansal and Dutta (Africacrypt, 2020) that supports both signature compression and public key aggregation has communication and storage cost $\widetilde{\mathcal{O}}(n^2)$, whereas our communication and storage cost is $\mathcal{O}(n)$. Our multi-signature scheme is in the plain public key model where the special registration of the public key is not necessary and it is secure under the rogue key attack. Our multi-signature scheme is secure under the hardness of ring short integer solution problem in the random oracle model.

Abstract A nominative signature (NS) is a cryptographic primitive where two parties collude to produce a signature. It is a user certification system and has applications in a variety of sectors where nominee cannot trust heavily on the nominator to validate the nominee's certificate and only targeted entities are allowed to verify the signature on sensitive data. A new construction for NS from standard assumptions on lattice is provided. The authors’ construction relies on collision‐resistant preimage sampleable function and symmetric key primitives like collision‐resistant pseudorandom function and zero knowledge proof system ZKB ++ for Boolean circuits. The authors provide detailed security analysis and show that their construction achieves security under unforgeability , invisibility , impersonation , and non‐repudiation in the existing model. Furthermore, our construction exhibits non‐transferability . The security under non‐repudiation is achieved in the quantum random oracle model using Unruh transform to ZKB ++ .