Zerocash: Decentralized Anonymous Payments from Bitcoin, by Eli Ben-Sasson and Alessandro Chiesa and Christina Garman and Matthew Green and Ian Miers and Eran Tromer and Madars Virza
Bitcoin is the first digital currency to see widespread adoption. While payments are conducted between pseudonyms, Bitcoin cannot offer strong privacy guarantees: payment transactions are recorded in a public decentralized ledger, from which much information can be deduced. Zerocoin (Miers et al., IEEE S&P 2013) tackles some of these privacy issues by unlinking transactions from the payment\'s origin. Yet, it still reveals payments\' destinations and amounts, and is limited in functionality.
In this paper, we construct a full-fledged ledger-based digital currency with strong privacy guarantees. Our results leverage recent advances in zero-knowledge Succinct Non-interactive ARguments of Knowledge (zk-SNARKs).
First, we formulate and construct decentralized anonymous payment schemes (DAP schemes). A DAP scheme enables users to directly pay each other privately: the corresponding transaction hides the payment\'s origin, destination, and transferred amount. We provide formal definitions and proofs of the construction\'s security.
Second, we build Zerocash, a practical instantiation of our DAP scheme construction. In Zerocash, transactions are less than 1 kB and take under 6 ms to verify --- orders of magnitude more efficient than the less-anonymous Zerocoin and competitive with plain Bitcoin.
Distributed Smooth Projective Hashing and its Application to Two-Server PAKE, by Franziskus Kiefer and Mark Manulis
Smooth projective hash functions have been used as building block for various cryptographic applications, in particular for password-based authentication.
In this work we propose the extended concept of distributed smooth projective hash functions where the computation of the hash value is distributed across $n$ parties and show how to instantiate the underlying approach for languages consisting of Cramer-Shoup ciphertexts.
As an application of distributed smooth projective hashing we build a new framework for the design of two-server password authenticated key exchange protocols, which we believe can help to \"explain\" the design of earlier two-server password authenticated key exchange protocols.
Ph.D. / M.Sc. Scholarships and Summer Internship, Cryptography, Security, and Privacy Research Group, Koç University, Istanbul, Turkey
Cryptography, Security & Privacy Research Group at Koç University has multiple openings for both M.Sc. and Ph.D. level applications. All accepted applicants will receive competitive scholarships including tuition waiver, housing, monthly stipend, computer, travel support, etc.
For more information about our group and projects, visit
For questions, contact Asst. Prof. Alptekin Küpçü
For applying online, and questions about the application-process, visit
For summer internship opportunities, visit
Professor in Cryptography (W1 - non-tenured), Ruhr-Universität Bochum, Germany
The Ruhr-Universität Bochum (RUB) is one of Germany’s leading research universities with more than 50 scientists working in IT-security and cryptography. The Faculty of Mathematics invites applications for the position of a Junior Professor (W1) in Cryptography to start as soon as possible.
The future holder of the position will represent the subject in research and teaching.
We are seeking a candidate with an excellent research record in cryptography, in particular in theoretical cryptography, provable security, protocols, or secure multi-party computation.
The position is non-tenured with an initial appointment for 3 years, and renewable for another 3 years after a positive mid-term review.
Candidates for the professorship are expected to have strong leadership qualities, particularly
• excellent level of commitment in academic teaching
• willingness to participate in interdisciplinary research
• willingness and ability to attract externally funded research projects
• or to contribute to joint research projects of the department.
Private Predictive Analysis on Encrypted Medical Data, by Joppe W. Bos and Kristin Lauter and Michael Naehrig
Increasingly, confidential medical records are being stored in data centers hosted by hospitals or large companies. As sophisticated algorithms for predictive analysis on medical data continue to be developed, it is likely that, in the future, more and more computation will be done on private patient data. While encryption provides a tool for assuring the privacy of medical information, it limits the functionality for operating on such data. Conventional
encryption methods used today provide only very restricted possibilities or none at all to operate on encrypted data without decrypting it first. Homomorphic encryption provides a tool for
handling such computations on encrypted data, without decrypting the data, and without even needing the decryption key.
In this paper, we discuss possible application scenarios for homomorphic encryption in order to ensure privacy of sensitive medical data. We describe how to privately conduct predictive analysis tasks on encrypted data using homomorphic encryption. As a proof of concept, we present a working implementation of a prediction service running in the cloud (hosted on Microsoft\'s Windows Azure), which takes as input private encrypted health data, and returns the probability of suffering cardiovascular disease in encrypted form. Since the cloud service uses homomorphic encryption, it makes this prediction while handling only encrypted data, learning nothing about
the submitted confidential medical data.
A Tamper and Leakage Resilient Random Access Machine, by Sebastian Faust and Pratyay Mukherjee and Jesper Buus Nielsen and Daniele Venturi
We present a ``universal\'\' Random Access Machine (RAM in short) for tamper and leakage resilient computation. The RAM has one CPU that accesses three storages (called disks in the following), two of them are secret, while the other one is public. The CPU has constant size for each fixed value of security parameter $k$. We construct a compiler for this architecture which transforms any keyed primitive into a RAM program where the key is encoded and stored on the two secret disks and the instructions for evaluating the functionality are stored on the public disk.
The compiled program tolerates arbitrary independent tampering of the disks. That is, the adversary can tamper with the intermediate values produced by the CPU, and the program code of the compiled primitive on the public disk. In addition, it tolerates bounded independent leakage from the disks and continuous leakage from the communication channels between the disks and the CPU.
Although it is required that the circuit of the CPU is tamper and leakage proof, its design is independent of the actual primitive being computed and its internal storage is non-persistent, i.e., all secret registers are reset between invocations. Hence, our result can be interpreted as reducing the problem of shielding arbitrary complex computations to protecting a single, simple and ``universal\'\' component. As a main ingredient of our construction we use continuous
non-malleable codes that satisfy certain additional properties.
A Strong and Efficient Certificateless Digital Signature Scheme, by Mohammed Alfateh Hassouna and Mohsin Hashim
This paper extends the certificateless public key infrastructure model that was proposed by Hassouna et al by proposing new digital signature scheme to provide true non-repudiation,
the proposed signature scheme is short and efficient, it is also has strength point that the KGC has no contribution in signature generation/verification process, therefore any compromise
of the KGC does not affect the non-repudiation service of the system. Furthermore, even the KGC cannot do signature forgery by (temporary) replacing the user\'s public key.