Privacy leakage in fuzzy commitment schemes

Abstract In 1999 Juels and Wattenberg introduced the fuzzy commitment scheme. Fuzzy commitment is a particular realization of a binary biometric secrecy system with a chosen secret key. Three cases of biometric sources are considered, i.e. memoryless and totally-symmetric biometric sources, memoryless and input-symmetric biometric sources, and memoryless biometric sources. It is shown that fuzzy commitment is only optimal for memoryless totally-symmetric biometric sources and only at the maximum secret-key rate. Moreover, it is demonstrated that for memoryless biometric sources, which are not input-symmetric, the fuzzy commitment scheme leaks information on both the secret key and the biometric data

Attribute-based encryption with encryption and decryption outsourcing

In this paper we propose a new scheme for ciphertext-policy attribute-based encryption that allows outsourcing of computationally expensive encryption and decryption steps. The scheme constitutes an important building block for mobile applications where both the host and users use mobile devices with limited computational power. In the proposed scheme, during encryption the host involves a semi-trusted proxy to encrypt a partially encrypted (by the host) message according to an access policy provided by the host. The proxy is unable to learn the message from this partially encrypted text. A user can only decrypt the stored ciphertext if he possesses secret keys associated with a set of attributes that satisfies the associated policy. To reduce computational load in the decryption step, the user, in his turn, involves a semi-trusted proxy (e.g. a cloud) by deploying the scheme of Green et al. (2011). The cloud is given a transformation key that facilitates construction of an El Gamal-ciphertext from the original ciphertext if the user\u27s attributes satisfy the ciphertext. This El Gamal-ciphertext can be then efficiently decrypted on the user\u27s resource-constrained device. The resulting ABE scheme with encryption and decryption outsourcing is proven to be secure in the generic group model

Authentication and authorisation in entrusted unions

This paper reports on the status of a project whose aim is to implement and demonstrate in a real-life environment an integrated eAuthentication and eAuthorisation framework to enable trusted collaborations and delivery of services across different organisational/governmental jurisdictions. This aim will be achieved by designing a framework with assurance of claims, trust indicators, policy enforcement mechanisms and processing under encryption to address the security and confidentiality requirements of large distributed infrastructures. The framework supports collaborative secure distributed storage, secure data processing and management in both the cloud and offline scenarios and is intended to be deployed and tested in two pilot studies in two different domains, viz, Bio-security incident management and Ambient Assisted Living (eHealth). Interim results in terms of security requirements, privacy preserving authentication, and authorisation are reported

Authentication and authorisation in entrusted unions

This paper reports on the status of a project whose aim is to implement and demonstrate in a real-life environment an integrated eAuthentication and eAuthorisation framework to enable trusted collaborations and delivery of services across different organisational/governmental jurisdictions. This aim will be achieved by designing a framework with assurance of claims, trust indicators, policy enforcement mechanisms and processing under encryption to address the security and confidentiality requirements of large distributed infrastructures. The framework supports collaborative secure distributed storage, secure data processing and management in both the cloud and offline scenarios and is intended to be deployed and tested in two pilot studies in two different domains, viz, Bio-security incident management and Ambient Assisted Living (eHealth). Interim results in terms of security requirements, privacy preserving authentication, and authorisation are reported

Privacy leakage in fuzzy commitment schemes

In 1999 Juels and Wattenberg introduced the fuzzy commitment scheme. Fuzzy commitment is a particular realization of a binary biometric secrecy system with a chosen secret key. Three cases of biometric sources are considered, i.e. memory- less and totally-symmetric biometric sources, memoryless and input-symmetric biometric sources, and memoryless biometric sources. It is shown that fuzzy commitment is only optimal for memoryless totally-symmetric biometric sources and only at the maximum secret-key rate. Moreover, it is demonstrated that for memoryless biometric sources, which are not input-symmetric, the fuzzy com- mitment scheme leaks information on both the secret key and the biometric data

Fast and secure retrieval of DNA sequences

Sequence models are retrieved from a sequences index. The sequence models model DNA or RNA sequences stored in a database, and each comprises a finite memory tree source model and parameters for the finite memory tree source model. One or more DNA or RNA sequences stored in the database are identified as being most similar to a query DNA or RNA sequence based on fitting of the retrieved sequence models to the query DNA or RNA sequence. The sequence models may be context tree weighting (CTW) models {Sx, [theta]Sx} where Sx denotes the context tree model for the DNA or RNA sequence x stored in the database, and [theta]Sx denotes parameters of the context tree model Sx. The fitting may include, for each CTW model {Sx, [theta]Sx}, computing the codeword length for the query DNA or RNA sequence y using the CTW model {Sx, [theta]Sx}

Achieving secure fuzzy commitment scheme for optical PUFs

Fuzzy commitment of Juels and Wattenberg 1999 is a popular technique for designing secure systems based on noisy data. The scheme is easy to implement using standard error-correcting codes. However, secrecy of this scheme is only guaranteed when input data are generated by uniform i.i.d. sources, while typical input data (PUFs and biometrics) are not uniform. In this paper we address the problem of extracting robust independent uniformly distributed bits out of noisy data that can be used as entries to fuzzy commitment. The proposed techniques can serve as a building block of secure fuzzy commitment systems. © 2009 IEEE

Context trees for privacy-preserving modeling of genetic data

In this work, we use context trees for privacypreserving modeling of genetic sequences. The resulting estimated models are applied for functional comparison of genetic sequences in a privacy preserving way. Here we define privacy as uncertainty about the genetic source sequence given its model and use equivocation to quantify it. We evaluate the performance of our approach on publicly available human genomic data. The simulation results confirm that the context trees can be effectively used to detect similar genetic sequences while guaranteeing high privacy levels. However, a trade-off between privacy and utility has to be taken into account in practical applications

Attribute-based encryption

A system for attribute-based encryption comprises a first encrypter (11) and a second encrypter (12). The first encrypter (11) comprises an input unit (1) for determining a message and a policy over a set of attributes, wherein the policy comprises a plurality of components, and a first cryptographic unit (2) for generating an encrypted representation of the message and an encrypted representation of the plurality of components. The second encrypter (12) comprises a receiving unit (3) for receiving the encrypted representation of the message and the encrypted representation of the plurality of components, and a second cryptographic unit (4) for transforming the encrypted representation of the message and the encrypted representation of the plurality of components into an attribute-based encrypted message associated with the policy

Information leakage in fuzzy commitment schemes

In 1999, Juels and Wattenberg introduced the fuzzy commitment scheme. This scheme is a particular realization of a binary biometric secrecy system with chosen secret keys. It became a popular technique for designing biometric secrecy systems, since it is convenient and easy to implement using standard error-correcting codes. This paper investigates privacy- and secrecy-leakage in fuzzy commitment schemes. The analysis is carried out for four cases of biometric data statistics, i.e., memoryless totally symmetric, memoryless input-symmetric, memoryless, and stationary ergodic. First, the achievable regions are determined for the cases when data statistics are memoryless totally symmetric and memoryless input-symmetric. For the general memoryless and stationary ergodic cases, only outer bounds for the achievable rate-leakage regions are provided. These bounds, however, are sharpened for systematic parity-check codes. Given the achievable regions (bounds), the optimality of fuzzy commitment is assessed. The analysis shows that fuzzy commitment is only optimal for the memoryless totally symmetric case if the scheme operates at the maximum secret-key rate. Moreover, it is demonstrated that for the general memoryless and stationary ergodic cases, the scheme leaks information on both the secret and biometric data