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 IETE Technical Review , 2010, Abstract: A convertible authenticated encryption scheme allows a designated recipient to retrieve an authenticated ciphertext and convert the authenticated ciphertext into an ordinary signature. Recently, Lee, Hwang, and Tzeng proposed a new convertible authenticated encryption scheme based on the ElGamal cryptosystem. In this paper, we show that the Lee-Hwang-Tzeng scheme is not secure against chosen plaintext attacks. In addition, we give a solution to repair it.
 Lee Byung-Rae EURASIP Journal on Wireless Communications and Networking , 2007, Abstract: The current mobile broadcast systems do not provide efficient solution for consumption of service and content based on the user identity card such as a smartcard. This prevents users from consuming broadcast service and contents independent of a specific terminal (e.g., the one used for registration or purchase). To provide usage of broadcast services based on the user identity card, mutual authentication needs to be established among the service provider, the terminal, and the user identity card whenever the terminal is changed. The crucial element for this is assuring the service provider, the terminal, and the user identity card by authenticating each entity to the other entities. In this paper, we propose the new authentication scheme, which provides efficient scheme for three kinds of mutual authentications among the service provider, the terminal, and the user identity card. We also construct mobile broadcast DRM system based on the proposed authentication scheme for consumption of broadcast services with multiple terminals.
 Byung-Rae Lee EURASIP Journal on Wireless Communications and Networking , 2007, DOI: 10.1155/2007/56050 Abstract: The current mobile broadcast systems do not provide efficient solution for consumption of service and content based on the user identity card such as a smartcard. This prevents users from consuming broadcast service and contents independent of a specific terminal (e.g., the one used for registration or purchase). To provide usage of broadcast services based on the user identity card, mutual authentication needs to be established among the service provider, the terminal, and the user identity card whenever the terminal is changed. The crucial element for this is assuring the service provider, the terminal, and the user identity card by authenticating each entity to the other entities. In this paper, we propose the new authentication scheme, which provides efficient scheme for three kinds of mutual authentications among the service provider, the terminal, and the user identity card. We also construct mobile broadcast DRM system based on the proposed authentication scheme for consumption of broadcast services with multiple terminals.
 Journal of Applied Mathematics , 2013, DOI: 10.1155/2013/217480 Abstract: Anonymity of identity-based encryption (IBE) means that given a ciphertext, one cannot distinguish the target identity from a random identity. In this paper, we thoroughly discuss the anonymity of IBE systems. We found that the current definition of anonymity is obscure to describe some IBE systems, such as Gentry IBE system. Furthermore, current definition cannot express the degree of anonymity. So we divide the degree of anonymity into weak anonymity and strong anonymity based on indistinguishability between different games. For weakly anonymous IBE systems, the target identity in a ciphertext cannot be distinguished from a random identity. For strongly anonymous IBE systems, the whole ciphertext cannot be distinguished from a random tuple. We also discuss the type of anonymity and divide it into two types. Type 1 means that a random tuple can be seen as a valid ciphertext, while type 2 cannot. Based on our new definitions, we show that three famous IBE systems, Gentry IBE system, Boyen-Waters IBE system, and Lewko IBE system, have strong but different types of anonymity. 1. Introduction Shamir [1] proposed the concept of identity-based encryption (IBE) in 1984 to simplify the public key infrastructure. In an IBE system, public keys for users can be formed from arbitrary strings such as e-mail addresses, IP addresses, or other meaningful strings. Anyone can encrypt messages using the identity, and only the owner of the corresponding secret key can decrypt the messages. But Shamir did not give a concrete construction of IBE until Boneh and Franklin [2] presented the first practical IBE system based on groups with efficiently computable bilinear maps. Another but less efficient IBE system using quadratic residues was proposed by Cocks [3]. After that, many new IBE systems are proposed [4–11]. Anonymous IBE was first noticed by Boyen [12] and later formalized by Abdalla et al. [13, 14]. Roughly speaking, an IBE system is said to be recipient anonymous or simply anonymous if the ciphertext leaks no information about the recipient’s identity. In other words, an attack cannot distinguish the target identity from a random identity for a ciphertext. Recently, people found that the anonymity of IBE can help to construct public key encryption with keyword search (PEKS) systems [13, 15–17]. The first anonymous IBE system is Boneh-Franklin IBE system [2]. In fact, this system has intrinsic anonymity; that is, its semantic security equals anonymity. But Boneh-Franklin IBE system is proposed in the random oracle model [18]. Boyen and Waters [8] gave the first
 Information Technology Journal , 2007, Abstract: This research studies the latest research concept in Computer Security namely Identity Based Cryptography. To start with, the paper gives an introduction to the concept called Identity Based Encryption with Mediated RSA and then applies this concept to do secure transactions through Internet. The research also highlights on the future work that can be carried over in this area.
 David Naccache Computer Science , 2005, Abstract: In this paper, we present a variant of Waters' Identity-Based Encryption scheme with a much smaller public-key size (only a few kilobytes). We show that this variant is semantically secure against passive adversaries in the standard model.\smallskip In essence, the new scheme divides Waters' public key size by a factor $\ell$ at the cost of (negligibly) reducing security by $\ell$ bits. Therefore, our construction settles an open question asked by Waters and constitutes the first fully secure {\sl practical} Identity-Based Encryption scheme
 Mei Cai Journal of Computer and Communications (JCC) , 2019, DOI: 10.4236/jcc.2019.72002 Abstract: Broadcast encryption (BE) allows a sender to broadcast its message to a set of receivers in a single ciphertext. However, in broadcast encryption scheme, ciphertext length is always related to the size of the receiver set. Thus, how to improve the communication of broadcast encryption is a big issue. In this paper, we proposed an identity-based homomorphic broadcast encryption scheme which supports an external entity to directly calculate ciphertexts and get a new ciphertext which is the corresponding result of the operation on plaintexts without decrypting them. The correctness and security proofs of our scheme were formally proved. Finally, we implemented our scheme in a simulation environment and the experiment results showed that our scheme is efficient for practical applications.
 International Journal of Computer Technology and Applications , 2011, Abstract: We propose a fully functional identity-based encryption scheme (IBE). The scheme has chosen cipher text security in the random oracle model assuming a variant of the computational Diffie-Hellman problem. Our system is based on bilinear maps between groups. The Weil pairing on elliptic curves is an example of such a map. We give precise definitions for secure identity based encryption schemes and give several applications for such systems. Trustworthy computing modules like secure coprocessors (ScP) are already in extensive use today, albeit limited predominantly to scenarios where constraints on cost is not a serious limiting factor. However, inexpensive trustworthy computers are required for many evolving application scenarios. The problem of realizing inexpensive ScPs for large-scale networks consisting of low complexity devices have not received adequate consideration thus far. We introduce two strategies toward realizing low-cost ScPs. The first is the decrypt only when necessary (DOWN) policy, which can substantially improve the ability of low-cost ScPs to protect their secrets. The DOWN policy relies on the ability to operate with fractional parts of secrets. Taking full advantage of the DOWN policy requires consideration of the nature of computations performed with secrets and even the mechanisms employed for distribution of secrets
 电子与信息学报 , 2008, Abstract: In this paper, the concepts of identity-based linkable ring signature and linkable convertible ring signature are proposed. Taken Zhang and Kim’s scheme as an example, a general method is given to add linkability and convertibility to some identity-based ring signatures. Then two efficient schemes are given for the first time, besides the complete anonymity and unforgeability under adaptively chosen message attack, one satisfying linkability, and the other satisfying both linkability and convertibility.
 计算机应用 , 2008, Abstract: Identity Based Encryption(IBE) schemes and Identity Based Broadcast Encryption(IBBE) schemes are often constructed by using bilinear maps (a.k.a. parings) on elliptic curves. In this paper, an Identity Based Broadcast Encryption scheme without pairings was given. It is secure in Random Oracle according to the Quadratic Residuosity assumption.
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