Fully Secure Identity-based Broadcast Encryption in the Subgroups

In this paper,we show how to use the dual techniques in the subgroups to give a secure identity-based broadcast encryption(IBBE) scheme with constant-size ciphertexts. Our scheme achieves the full security(adaptive security) under three static(i.e. non q-based) assumptions. It is worth noting that only recently Waters gives a short ciphertext broadcast encryption system that is even adaptively secure under the simple assumptions. One feature of our methodology is that it is relatively simple to leverage our techniques to get adaptive security.

An Efficient Identity-Based Homomorphic Broadcast Encryption

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.

Implementing Broadcast Encryption Scheme Using Bilinear Map and Group Characteristic

This paper introduced a novel method for implementing broadcast encryption. Our scheme takes advantages of bilinear map and group characteristic, and shifts most of the storage overhead to the public device instead of storing in the tamper-proof device which is a major problem on current implementation. Furthermore, the broadcast keys in our scheme could be reused periodically resulting in more operational efficiency.

Identity-based Broadcast Encryption with Shorter Transmissions

This paper describes two identity-based broadcast encryption （IBBE） schemes for mobile ad hoc networks. The first scheme proposed achieves sub-linear size cipertexts and the second scheme achieves O（1）- size ciphertexts. Furthermore, when the public keys are transmitted, the two schemes have short transmissions and achieve O（1） user storage cost, which are important for a mobile ad hoc network. Finally, the proposed schemes are provable security under the decision generalized bilinear Diffi-Hellman （GBDH） assumption in the random oracles model.

Identity-based encryption with wildcards in the standard model

In this article, based on Chatterjee-Sarkar＇ hierarchical identity-based encryption （HIBE）, a novel identity-based encryption with wildcards （WIBE） scheme is proposed and is proven secure in the standard model （without random oracle）. The proposed scheme is proven to be secure assuming that the decisional Bilinear Diffie-Hellman （DBDH） problem is hard. Compared with the Wa-WIBE scheme that is secure in the standard model, our scheme has shorter common parameters and ciphertext length.

Revocable Hierarchical Identity-Based Broadcast Encryption

Hierarchical Identity-Based Broadcast Encryption （HIBBE） organizes users into a tree-like structure, and it allows users to delegate their decryption ability to subordinates and enable encryption to any subset of users while only intended users can decrypt. However, current HIBBE schemes do not support efficient revocation of private keys. Here, a new primitive called Revocable Hierarchical Identity-Based Broadcast Encryption （RHIBBE） is formalized that allows revocation of the HIBBE. Ciphertext indistinguishability is defined against the selectively Bounded Revocable Identity-Vector-Set and Chosen-Plaintext Attack （IND-sBRIVS-CPA）. An IND-sBRIVS-CPA secure RHIBBE scheme is constructed with efficient revocation on prime-order bilinear groups. The unbounded version of the scheme is also shown to be secure but a little weaker than the former under the decisional n-Weak Bilinear Diffie-Hellman inversion assumption.

ID-based authentication scheme combined with identity-based encryption with fingerprint hashing

Current identity-based （ID） cryptosystem lacks the mechanisms of two-party authentication and user＇s private key distribution. Some ID-based signcryption schemes and ID-based authenticated key agreement protocols have been presented, but they cannot solve the problem completely. A novel ID-based authentication scheme based on ID-based encrypfion （IBE） and fingerprint hashing method is proposed to solve the difficulties in the IBE scheme, which includes message receiver authenticating the sender, the trusted authority （TA） authenticating the users and transmitting the private key to them. Furthermore, the scheme extends the application of fingerprint authentication from terminal to network and protects against fingerprint data fabrication. The fingerprint authentication method consists of two factors. This method combines a token key, for example, the USB key, with the user＇s fingerprint hash by mixing a pseudo-random number with the fingerprint feature. The security and experimental efficiency meet the requirements of practical applications.

Constructing pairing-free certificateless public key encryption with keyword search

Searchable public key encryption enables a storage server to retrieve the publicly encrypted data without revealing the original data contents.It offers a perfect cryptographic solution to encrypted data retrieval in encrypted data storage systems.Certificateless cryptography(CLC)is a novel cryptographic primitive that has many merits.It overcomes the key escrow problem in identity-based cryptosystems and the cumbersome certificate problem in conventional public key cryptosystems.Motivated by the appealing features of CLC,three certificateless encryption with keyword search(CLEKS)schemes were presented in the literature.However,all of them were constructed with the costly bilinear pairing and thus are not suitable for the devices that have limited computing resources and battery power.So,it is interesting and worthwhile to design a CLEKS scheme without using bilinear pairing.In this study,we put forward a pairing-free CLEKS scheme that does not exploit bilinear pairing.We strictly prove that the scheme achieves keyword ciphertext indistinguishability against adaptive chosen-keyword attacks under the complexity assumption of the computational Diffie-Hellman problem in the random oracle model.Efficiency comparison and the simulation show that it enjoys better performance than the previous pairing-based CLEKS schemes.In addition,we briefly introduce three extensions of the proposed CLEKS scheme.

A Certificateless Threshold Public Key Encryption Scheme

The decryption participant＇s private key share for decryption is delegated by key generation center in the threshold IBE scheme.However,a key generation center which is absolutely trustworthy does not exist.So the author presents a certificateless threshold public key encryption scheme.Collaborating with an administrator,the decryption participant generates his whole private key share for decryption in the scheme.The administrator does not know the decryption participant＇s private key share for decryption.Making use of q-SDH assumption,the author constructs a certificateless threshold public key encryption scheme.The security of the scheme is eventually reduced to the solving of Decisional Bilinear Diffie-Hellman problem.Moreover,the scheme is secure under the chosen ciphertext attack in the standard model.

A Hierarchical Attribute-Based Encryption Scheme

According to the relation of an attribute set and its subset,the author presents a hierarchical attribute-based encryption scheme in which a secret key is associated with an attribute set.A user can delegate the private key corresponding to any subset of an attribute set while he has the private key corresponding to the attribute set.Moreover,the size of the ciphertext is constant,but the size of private key is linear with the order of the attribute set in the hierarchical attribute-based encryption scheme.Lastly,we can also prove that this encryption scheme meets the security of IND-sSETCPA in the standard model.

Secure Proxy Re-Encryption from CBE to IBE

In this paper, an efficient hybrid proxy re-encryption scheme that allows the transformation of the ciphertexts in a traditional public key cryptosystem into the ciphertexts in an identity-based system is proposed. The scheme is non-interactive, unidirectional and collude ＂safe＂. Furthermore, it is compatible with current IBE （identity-based encryption） deployments. The scheme has chosen ciphertext security in the random oracle model assuming the hardness of the Decisional Bilinear Diffie-Hellman problem.

基于合数阶双线性群的多用户陷门不可区分可搜索加密方案

可搜索加密是云存储环境下密文检索的主要技术。针对以去除安全信道构造的公共密钥可搜索加密方案SCF-PEKS加密时依赖用户公钥导致搜索服务限于单一用户,及无安全信道的可搜索加密方式容易遭受外部敌手的关键字猜测攻击等问题,分析并证明了现有多用户可搜索加密方案存在关键字陷门易遭受攻击的安全缺陷,在使用合数阶双线性对基础上提出一种多用户可搜索加密方案,并基于判定性子群假设和DBDH假设证明论文算法满足关键字陷门不可区分性的安全要求,可以抵御外部敌手选择关键字攻击。对比文献分析显示,在没有明显增加计算复杂度的前提下,提出的加密方案陷门尺寸及密文尺寸良好、安全性更高。

基于商密SM9算法同态加密方案

同态加密(homomorphic encryption,HE)被认为是隐私保护应用中最重要的密码技术之一.SM9算法是我国发布的商用密码算法标准,但SM9算法并不满足同态的属性.以SM9的算法为基础,设计一种基于PKI体制且具有同态性质的加密方案,使得新设计的算法同时具备加法和乘法同态性质,即满足任意次密文加法运算和1次密文乘法运算,且密文经过乘法运算后仍然满足加法同态性质以及标量乘,适合2次多项式的隐私计算.该方案具备选择明文攻击(IND-CPA)安全性.

一个高效的随机化的可验证加密签名方案

在基于对的可验证加密签名方案中,对运算是最为耗时的,故应在此类方案中尽量减少对运算的次数.为此,在给出一个新的基于对的签名方案的基础上,给出一个新的随机化可验证加密签名方案.新方案具有最少的对运算,即只有一个对运算.因此,与类似的方案相比,新方案更为有效.方案的安全性依赖于k-合谋攻击问题和离散对数问题困难假设.

基于国密SM9的可搜索加密方案

为满足密文数据安全级别的要求,现有基于身份的可搜索加密方案多次使用安全参数较大的对称双线性对运算,导致计算效率降低,且其密钥形式难以与国家商用密码算法SM9相结合。针对该问题,设计一种基于SM9密码算法的可搜索加密方案。在离散椭圆曲线的两个子群中分别生成用户的公私钥对,使方案的密钥形式与SM9密码算法保持一致,解决经SM9密码算法加密后数据的检索问题,同时结合SM9密码算法,基于非对称双线性特性在确保方案安全性的同时提高检索效率。根据双线性对的性质分析该方案的正确性和安全性,并验证其满足在随机谕言模型下的适应性密文不可区分性和陷门不可区分性。仿真结果表明,与EdIBEKS、PEAKS、dIBAEKS方案相比,该方案在索引生成算法、陷门生成算法和检索匹配算法上的计算效率分别平均提高了77%、16.67%、28%以上。

基于无证书的可验证加密签名方案

无证书密码体制实现无公钥证书且没有密钥托管的性质。将无证书加密方案与可验证加密方案相结合,提出了一种基于无证书的可验证加密签名方案(Certificateless Verifiably Encryption Signature scheme简称CVES),并给予该方案的正确性和不可伪造证明,该方案能有效地克服恶意签名和合谋攻击。

使用对技术的基于身份密码学研究综述

密钥管理是基于证书密码学中最复杂的问题,基于身份密码学正是为了简化密钥管理问题提出的.从保障信息安全的3个基本密码学要素(加密、数字签名和密钥协商)出发,对基于身份密码学的研究现状进行了综述,对其中存在的安全模型、执行效率等问题进行了详细分析.由于针对基于身份密码学缺乏实际应用研究,以解决无线移动IPv6网络环境下的接入控制和数据机密性问题为应用场景,讨论了一种基于身份密码技术的应用思路和问题,同时基于身份密码技术本身及其应用两方面指出了未来的研究趋势.

标准模型下安全的基于证书密钥封装方案

混合加密是将公钥加密与对称加密结合的一种加密技术.将密钥封装机制引入到基于证书加密方案中,提出了基于证书密钥封装机制的形式化定义及安全模型,构造了一个基于证书密钥封装方案.基于判定双线性Diffie-Hellman困难问题假定,在标准模型下证明提出的方案是自适应选择密文安全的.

可证安全的基于证书广播加密方案

广播加密可使发送者选取任意用户集合进行广播加密,只有授权用户才能够解密密文.但是其安全性依赖广播中心产生和颁布群成员的解密密钥.针对这一问题,本文提出基于证书广播加密的概念,给出了基于证书广播加密的形式化定义和安全模型.结合基于证书公钥加密算法的思想,构造了一个高效的基于证书广播加密方案,并证明了方案的安全性.在方案中,用户私钥由用户自己选取,证书由认证中心产生,解密密钥由用户私钥和证书两部分组成,克服了密钥托管的问题.在方案中,广播加密算法中的双线性对运算可以进行预计算,仅在解密时做一次双线性对运算,提高了计算效率.

TinyIBE:面向无线传感器网络的身份公钥加密系统

由于无线传感器网络节点的资源受限,大部分公钥加密算法被认为无法适用。最近的研究则显示椭圆曲线加密算法ECC(Elliptic Curve Cryptography)在无线传感器节点上运算可行,基于身份的公钥密码体制IBE也因此成为研究热点,但尚无出现完整的解决方案。在分析面向TinyOS的公钥算法相关研究工作基础上,设计实现了一套基于Tate对的身份公钥加密系统TinyIBE。首先给出椭圆曲线选择及Tate对参数优化过程,再设计在线和离线PKG两种应用方案,最后在MICA2节点上给出测试结果。