Reflections on the security proofs of Boneh-Franklin identity-based encryption scheme

In this paper, we first review the existing proofs of the Boneh-Franklin identity-based encryption scheme (BF-IBE for short), and show how to admit a new proof by slightly modifying the specifications of the hash functions of the original BF-IBE. Compared with prior proofs, our new proof provides a tighter security reduction and minimizes the use of random oracles, thus indicates BF-IBE has better provable security with our new choices of hash functions. The techniques developed in our proof can also be applied to improving security analysis of some other IBE schemes. As an independent technical contribution, we also give a rigorous proof of the Fujisaki-Okamoto (FO) transformation in the case of CPA-to-CCA, which demonstrates the efficiency of the FO-transformation (CPA-to-CCA), in terms of the tightness of security reduction, has long been underestimated. This result can remarkably benefit the security proofs of encryption schemes using the FO-transformation for CPA-to-CCA enhancement.

The differential fault analysis on block cipher FeW

Feather weight(FeW)cipher is a lightweight block cipher proposed by Kumar et al.in 2019,which takes 64 bits plaintext as input and produces 64 bits ciphertext.As Kumar et al.said,FeW is a software oriented design with the aim of achieving high efficiency in software based environments.It seems that FeW is immune to many cryptographic attacks,like linear,impossible differential,differential and zero correlation attacks.However,in recent work,Xie et al.reassessed the security of FeW.More precisely,they proved that under the differential fault analysis(DFA)on the encryption states,an attacker can completely recover the master secret key.In this paper,we revisit the block cipher FeW and consider the DFA on its key schedule algorithm,which is rather popular cryptanalysis for kinds of block ciphers.In particular,by respectively injected faults into the 30th and 29th round subkeys,one can recover about 55/80~69%bits of master key.Then the brute force searching remaining bits,one can obtain the full master secret key.The simulations and experiment results show that our analysis is practical.