Anonymous Encryption Research Articles

Anonymous Homomorphic IBE with Application to Anonymous Aggregation

All anonymous identity-based encryption (IBE) schemes that are group homomorphic (to the best of our knowledge) require knowledge of the identity to compute the homomorphic operation. This paper is motivated by this open problem, namely to construct an anonymous group-homomorphic IBE scheme that does not sacrifice anonymity to perform homomorphic operations. Note that even when strong assumptions, such as indistinguishability obfuscation (iO), are permitted, no schemes are known. We succeed in solving this open problem by assuming iO and the hardness of the DBDH problem over rings (specifically, ZN2 for RSA modulus N). We then use the existence of such a scheme to construct an IBE scheme with re-randomizable anonymous encryption keys, which we prove to be IND-ID-RCCA secure. Finally, we use our results to construct identity-based anonymous aggregation protocols.

LacminCC: lightweight anonymous communication model in cloud computing

With increasing application of cloud computing and big data technologies, a large amount of personal information is stored on the Internet, which raises the issue of privacy leakage. To protect people’s data privacy, this paper firstly presents a new anonymous Identify-Based Encryption (IBE) scheme and gives the proof of its security under the Bilinear Diffie–Hellman Security Assumption. Then, by introducing the anonymous IBE scheme into anonymous communication fields, this paper introduces a new lightweight anonymous communication model for cloud computing, which guarantees the anonymity of system users and the security of messages in small groups. Our analysis shows that, the proposed communication model cannot only reduce memory consumption and improve message transmission efficiency, but also effectively resist traffic-analysis attacks, node eavesdropping, and finally achieve secure anonymous communication in cloud computing.

Research on a New Attribute Encryption Anonymous Algorithm in Cloud Computing Environment

The attribute encryption anonymous model is used to encrypt data and protect anonymity in cloud computing environment, so as to realize attribute encryption and privacy protection in cloud computing environment. In order to improve the self-adaptability and accurate control of data encryption in cloud computing environment, an anonymous data encryption algorithm based on hyperbolic cyclic mapping is proposed. The priority list control model of adaptive privacy protection for cloud data is constructed. The load balancing control and encryption key design of anonymous big data with hyperbolic cyclic mapping are implemented by using bilinear differential control protocol. The hyperbolic differential equation control and adaptive weighting method are used to construct the key function for anonymous encryption of cloud computing data. The time window and privacy protection protocol of attribute encryption anonymous control is optimized by slot allocation. The encryption anonymous algorithm is improved. Simulation results show that the adaptive equalization performance of attribute anonymous encryption in cloud computing environment is better, the ability of anti-attack is better, and the recall rate of data is better than the traditional method.

Fully secure hierarchical inner product encryption for privacy preserving keyword searching in cloud

Cloud computing provides dynamically scalable resources provisioned as a service over networks. But untrustworthy cloud service provider (CSP) offers a big obstacle for the adoption of the cloud service since CSP can access data in cloud without data owner's permission. Hierarchical inner product encryption (HIPE) covers all applications of anonymous encryption, fully private communication and search on encrypted data, which provide trusted data access control policy to CSP. However, the existing works only achieve either selectively attribute-hiding or adaptively attribute-hiding under some strong assumptions in the public key setting. These schemes only support limited class of functions and can not protect the privacy of the query. To overcome these shortcomings, a novel HIPE in private key setting is issued. The proposed scheme achieves both fully secure and security reduction under the decisional linear (DLIN) assumption in the standard model. It has longer-size secret keys and size ciphertexts and b...

Robust Encryption

We provide a provable-security treatment of "robust" encryption. Robustness means it is hard to produce a ciphertext that is valid for two different users. Robustness makes explicit a property that has been implicitly assumed in the past. We argue that it is an essential conjunct of anonymous encryption. We show that natural anonymity-preserving ways to achieve it, such as adding recipient identification information before encrypting, fail. We provide transforms that do achieve it, efficiently and provably. We assess the robustness of specific encryption schemes in the literature, providing simple patches for some that lack the property. We explain that robustness of the underlying anonymous IBE scheme is essential for public-key encryption with keyword search (PEKS) to be consistent (meaning, not have false positives), and our work provides the first generic conversions of anonymous IBE schemes to consistent (and secure) PEKS schemes. Overall, our work enables safer and simpler use of encryption.

Anonymous encryption with partial‐order subset delegation and its application in privacy email systems

In privacy-carrying email systems, the authors should guarantee that the email content is confidential and sometimes the sender/receiver identities are hidden. Also, they require that the key generation is flexible and manageable. In this study, first, they propose an anonymous encryption scheme that supports a partial-order subset delegatable ability. The proposed scheme achieves the security properties of confidentiality against adaptive chosen-plaintext attacks, anonymity against adaptive chosen-subset attacks and computational delegation indistinguishability. Secondly, they provide a deployment application of their anonymous encryption in an interdisciplinary group email management system with flexible and fine-grained key delegation. The deployment can achieve the privacy of message confidentiality, receiver anonymity and delegation obliviousness, which has fine-grained security in secure email systems. Finally, they provide an extension for the chosen-ciphertext secure scheme, and discuss the efficiency for decryption and the security level.

Generic Constructions and Transformations of Decryption Consistent Encryption

ABSTRACTBinding encryption provides an effective way to broadcast a secret to an authorized group of users, which guarantees decryption consistency, i.e., that all users can obtain the same message without any interaction among them. In this paper, we first give the definition of security of a binding encryption, and then construct a primitive that achieves security against chosen plaintext attacks (CPA) and decryption consistency. This primitive is derived from a CPA-secure public-key encryption (PKE) scheme. Then, we present several transformations of binding encryption, which ensure some advanced security requirements such as anonymity, strong decryption consistency, and non-malleability.(1) Negative results that: (a) A CCA (chosen-ciphertext attack) secure PKE does not imply a CCA-secure multi-receiver encryption (ME) or binding encryption; (b) an anonymous CPA-secure PKE implies an anonymous ME but does not imply any anonymous binding encryption; (c) a CCA-secure anonymous PKE does not imply a CCA-secure anonymous ME or anonymous binding encryption.(2) A generic construction for a binding encryption that: (a) Uses CPA-secure PKE and symmetric encryption to construct a CPA-secure ME; (b) uses a CPA-secure ME and a polynomially verifiable function to construct a CPA-secure binding encryption.(3) Three transformations from (anonymous) CCA-secure PKE to (anonymous) CCA-secure binding encryption: the first one is based on a strong one-time signature, the second one is derived from a trapdoor pseudo-random function, while the third one is based on (information-theoretically secure) cover-free families, and hence it does not require any additional computational assumptions.

Anonymous spatial encryption under affine space delegation functionality with full security

Anonymous encryption provides the decrypter’s identity privacy preservation as well as plaintext confidentiality. Spatial encryption, which is a kind of functional encryption, provides a generalized framework for special property encryption schemes such as broadcast encryption, predicate encryption, forward secure encryption, (hierarchical) identity-based encryption, delegatable attribute-based encryption etc. In this paper, we propose an anonymous spatial encryption scheme that deploys an affine subspace delegation mechanism. Our proposed scheme captures the message confidentiality, recipient anonymity, adaptive security, partial-order delegation and short ciphertext, simultaneously. To the best of our knowledge, the proposed scheme is the first anonymous spatial encryption that provides the anonymity property in adaptive security model, whose construction is based on a dual system encryption mechanism in bilinear composite-order groups. We also give a conversion construction to move into a prime-order setting with canceling property, whose security is based on the Decision Linear Problem. Finally, we provide a transformation methodology to obtain a CCA-secure scheme that combines a one-time signature, delegation functionality and the CPA-secure scheme.

New Techniques for Anonymous HIBE with Short Ciphertexts in Prime Order Groups

Anonymous hierarchical identity based encryption (HIBE) is an extension of identity based encryption (IBE) that can use an arbitrary string like an e-mail address for a public key, and it additionally provide the anonymity of identity in ciphertexts. Using the anonymous HIBE schemes, it is possible to construct anonymous communication systems and public key encryption with keyword search. This paper presents an anonymous HIBE scheme with constant size ciphertexts under prime order symmetric bilinear groups, and shows that it is secure under the selective security model. Previous anonymous HIBE schemes were constructed to have linear size ciphertexts, to use composite order bilinear groups, or to use asymmetric bilinear groups that is a special type of bilinear groups. Our construction is the first efficient anonymous HIBE scheme that has constant size ciphertexts and that uses prime order symmetric bilinear groups. Compared to the previous scheme of composite order bilinear groups, ours is ten times faster. To achieve our construction, we first devise a novel cancelable random blinding technique. The random blinding property of our technique provides the anonymity of our construction, and the cancellation property of our technique enables decryption.

Unconditionally Secure Anonymous Encryption and Group Authentication

Anonymous channels or similar techniques that achieve sender's anonymity play important roles in many applications, e.g. electronic voting. However, they will be meaningless if cryptographic primitives containing sender's identity are carelessly used during the transmission. In computationally secure settings, this problem may be easily overcome by using public key encryption and group signatures. However, in an unconditionally secure setting, in which no computational difficulty is assumed, this is not an easy case as such. As the increasing computational power approaches the point where security policy can no longer assume the difficulty of solving factoring or discrete logarithm problems, it must shift its focus to assuring the solvency of unconditionally secure schemes that provide long-term security. The main contribution of this paper is to study the security primitives for the above problem. In this paper, we first define the unconditionally secure asymmetric encryption scheme, which is an encryption scheme with unconditional security and where it is impossible for a receiver to deduce the identity of a sender from the encrypted message. We also investigate tight lower bounds on required memory sizes from an information theoretic viewpoint and show an optimal construction based on polynomials. It is remarkable to see that these bounds are considerably different from those in Shannon's model of the conventional unconditionally secure symmetric encryption. Other than the polynomial-based scheme, we also show a construction based on combinatorial theory, a non-malleable scheme and a multi-receiver scheme. Then, we define and formalize the group authentication code (GA-code), which is an unconditionally secure authentication code with anonymity like group signatures. In this scheme, any authenticated user will be able to generate and send an authenticated message while the receiver can verify the legitimacy of the message---that it has been sent from a legitimate user but at the same time retains his anonymity. However, by cooperating with the group authority, such as in the case of disputes, the receiver is able to obtain information of the user's identity. For GA-code, we show two concrete constructions.