Protecting against key-exposure: strongly key-insulated encryption with optimal threshold

Key-insulated encryption schemes use a combination of key splitting and key evolution to protect against key exposure. Existing schemes, however scale poorly, having cost proportional to the number t of time periods that may be compromised by the adversary, and thus are practical only for small values of t. Yet in practice t might be large. This paper presents a strongly key-insulated encryption scheme with optimal threshold. In our scheme, t need not be known in advance and can be as large as one less than the total number of periods, yet the cost of the scheme is not impacted. This brings key-insulated encryption closer to practice. Our scheme is based on the Boneh-Franklin identity-based encryption (IBE) scheme [9], and exploits algebraic properties of the latter. Another contribution of this paper is to show that (not strongly) key-insulated encryption with optimal threshold and allowing random-access key updates (which our scheme and all others known allow) is equivalent to a restricted form of IBE. This means that the connection between key-insulated encryption and IBE is not accidental. Supported in part by NSF grants CCR-0098123, ANR-0129617 and CCR-0208842, and by an IBM Faculty Partnership Development Award. Supported in part by an NSF graduate fellowship.     

ID-based threshold decryption secure against adaptive chosen-ciphertext attack

This paper proposes an identity-based threshold decryption scheme IB-ThDec and reduces its security to the Bilinear Diffie-Hellman problem. Compared with previous work, this conceals two pairing computations in the ciphertext validity verification procedure. The formal proof of security of this scheme is provided in the random oracle model. Additionally, we show that IB-ThDec can be applied to the threshold key escrow and the mediated cryptosystems.     

基于身份的电子印章设计与实现

随着办公自动化的发展,电子文档逐渐取代了传统的纸制文档。电子印章可以有效保障企业办公自动化中电子文档的安全性。在分析现有电子印章的签名方案的基础上,提出基于身份的电子印章的设计方法,给出基于身份电子印章系统的构架和相应的签名算法。最后指出该方法安全性以及特点。     

Efficient identity-based GQ multisignatures

ISO/IEC 14888 specifies a variety of digital signature mechanisms to sign messages of arbitrary length. These schemes can be applied to provide entity authentication, data origin authentication, non-repudiation, and data integrity verification. ISO/IEC 14888 consists of three parts under the general title Information technology—Security techniques—Digital signatures. Part II, or ISO/IEC 14888-2 specifies the general structure and the fundamental procedures for the generation and verification of an identity-based signature (IBS) mechanism for messages of arbitrary length. Particularly, the IBS scheme of Guillou and Quisquater (GQ) is described in Clauses 6–8. In this paper, an efficient identity-based multisignature (IBMS) scheme is proposed for the GQ IBS scheme, which allows multiple users using the ISO/IEC 14888-2 standard GQ scheme to generate multisignatures. The scheme is efficient in the sense that both the length and the verification time of the multisignatures are fixed. The proposed ID-based multisignature scheme is also secure against forgeability under adaptive chosen-message attack and adaptive chosen-identity attack in random oracle model.     

A pairing-free identity-based authenticated key agreement protocol with minimal message exchanges

Based on the computational Diffie-Hellman problem, this paper proposes an identity-based authenticated key agreement protocol which removes bilinear pairings. Compared with previous protocols, the new protocol minimizes message exchange time with no extra cost. The protocol provides strong security guarantees including key compromise impersonation resilience, perfect forward secrecy, and master key forward secrecy. A security proof with the modular approach in the modified Bellare-Rogaway model is also provided.     

基于身份的椭圆曲线密码体制安全组播方案

提出一个应用椭圆曲线密码体制进行密钥协商而在基于身份的公钥密码系统内进行组通信的全新安全组播方案,分析子组成员的密钥协商和子组间的通信过程,以及组成员动态变化时密钥的更新过程。结果表明,该方案在降低计算和通信代价方面可取得较好的效果,且满足密钥协商的安全要求。     

An efficient and provable secure identity-based ring signcryption scheme

ID-based ring signcryption schemes (IDRSC) are usually derived from bilinear parings, a powerful but computationally expensive primitive. The number of paring computations of all existing ID-based ring signcryption schemes from bilinear pairings grows linearly with group size, which makes the efficiency of ID-based schemes over traditional schemes questionable. This paper presents a new identity-based ring signcryption scheme, which only takes four pairing operations for any group size and the scheme is proven to be indistinguishable against adaptive chosen ciphertext ring attacks (IND-IDRSC-CCA2) and existentially unforgeable against adaptive chosen message and identity attacks (EUF-IDRSC-ACMA) under the random oracle model.     

基于身份加密的装备密钥分布式生成算法

为解决身份加密体制中单一密钥生成中心易遭受攻击的问题,借鉴网络中心战“去中心化”的思想,针对Lewko-Waters身份加密协议,提出了一种分布式密钥生成算法。在算法中,主密钥由密钥生成中心和密钥隐私中心共同掌握,用户密钥在密钥生成中心监管下由分布于网络中的各密钥隐私中心共同生成,有利于增强Lewko-Waters协议密钥管理体系的抗毁性、鲁棒性。最后,在标准模型中证明了该方案在选择明文攻击下的密文不可区分性,并进行了算法性能比较分析。     

TinyPBC: Pairings for authenticated identity-based non-interactive key distribution in sensor networks

Key distribution in Wireless Sensor Networks (WSNs) is challenging. Symmetric cryptosystems can perform it efficiently, but they often do not provide a perfect trade-off between resilience and storage. Further, even though conventional public key and elliptic curve cryptosystems are computationally feasible on sensor nodes, protocols based on them are not, as they require the exchange and storage of large keys and certificates, which is expensive.Using Pairing-Based Cryptography (PBC) protocols parties can agree on keys without any interaction. In this work, we (i) show how security in WSNs can be bootstrapped using an authenticated identity-based non-interactive protocol and (ii) present TinyPBC, to our knowledge, the most efficient implementation of PBC primitives for 8, 16 and 32-bit processors commonly found in sensor nodes. TinyPBC is able to compute pairings, the most expensive primitive of PBC, in 1.90 s on ATmega128L, 1.27 s on MSP430 and 0.14 s on PXA27x.