In this paper we consider two security notions related to Identity Based Encryption: Key-insulated public key encryption, introduced by Dodis, Katz, Xu and Yung; and Timed-Release Public Key cryptography, introduced independently by May and Rivest, Shamir and Wagner. We first formalize the notion of secure timed-release cryptography, and show that, despite several differences in its formulation...

In this paper, using properties of Ramanujan sums and of the finite Fourier transform of arithmetic functions, we give an explicit formula for the number of solutions of the linear congruence a1x1 + · · · + akxk ≡ b (mod n), with (xi, n) = ti (1 ≤ i ≤ k), where a1, t1, . . . , ak, tk, b, n (n ≥ 1) are arbitrary integers. Some special cases of this problem have been studied in many papers, and h...

Identity-based encryption is a very convenient tool to avoid key management. Recipient-privacy is also a major concern nowadays. To combine both, anonymous identity-based encryption has been proposed. This paper extends this notion to stronger adversaries (the authority itself). We discuss this new notion, together with a new kind of non-malleability with respect to the identity, for several ex...

In 2013, Thadvai et al. proposed a novel authenticated encryption scheme with convertibility. They claimed that the proposed scheme satisfies all the properties of an ideal authenticated encryption scheme (AES). However, this paper shows that Thadvai et al.’s AES scheme still suffers from a forgery converted signature attack, that is, any one Corresponding author: Ki-Dong Bu ([email protected]) 27...