Abstract. We show how to realize two-factor authentication for a Bitcoin wal-let employing the two-party ECDSA signature protocol adapted from MacKen-zie & Reiter (2004). We also present a prototypic implementation of a Bitcoin wallet that offers both: two-factor authentication and verification over a sepa-rate channel. Since we use a smart phone as the second authentication factor, our solution can be used with hardware already available to most users and the user experience is quite similar to the existing online banking authentication methods. 1.
In response to the need for secure one-round authenticated key exchange protocols providing both perfect forward secrecy and full deniability, we put forward a new paradigm for constructing protocols from a Diffie-Hellman type protocol plus a non-interactive designated verifier proof of knowledge (DV-PoK) scheme. We define the notion of DV-PoK which is a variant of non-interactive zero-knowledge proof of knowledge, and provide an efficient DVPoK scheme as a central technical building block of our protocol. The DV-PoK scheme possesses nice properties such as unforgeability and symmetry which help our protocol to achieve perfect forward secrecy and full deniability respectively. Moreover, the security properties are formally proved in the Canetti-Krawczyk model under the Gap Diffie-Hellman assumption. In sum, our protocol offers a remarkable combination of salient security properties and efficiency, and the notion of DV-PoK is of independent interests.
J-PAKE is a Password-Authenticated Key Exchange protocol, proposed in 2008 and presented again in 2010 and 2011. It does not require any public key infrastructure but uses zero-knowledge proofs. J-PAKE has been submitted as a candidate for the IEEE P1363.2 standard for password-based public key cryptography, and included in OpenSSL and OpenSSH. Since December 2010, J-PAKE has been used in Mozilla Firefox web browser. In this paper, we show that J-PAKE is vulnerable to password compromise impersonation attack, replay attack, and unknown key-share attack. We also propose some improvements for thwarting replay and unknown key-share attacks.
In a hybrid network system which combines a wired network adopting PKI authentication and a wireless network adopting IBE authentication,it is difficult to authenticate other nodes in view of the different security polices and cryptosystem.To solve this problem,a cross-domain authentication scheme based on zero knowledge proof is proposed.An agency node is settled between the two heterogeneous trustworthy domains to certificate nodes'commitments in the zero knowledge proof.Then a authentication protocol between heterogeneous trustworthy domains is designed to realize the authentication between nodes in different domains,and the correctness,security and efficiency of the protocol are analyzed.The results show that the proposed protocol is feasible and effective.
Jan 1, 2014ยท25th IET Irish Signals & Systems Conference 2014 and 2014 China-Ireland International Conference on Information and Communities Technologies (ISSC 2014/CIICT 2014)
The advent of the IoT with an estimated 50 billion internet enabled devices by the year 2020 raises questions about the suitability and scalability of existing mechanisms to provide privacy, data integrity and end-entity authentication between communicating peers. In this paper we present a new protocol that combines zero-knowledge proofs and key exchange mechanisms to provide secure and authenticated communication in static M2M networks, therefore addressing all the above problems. The protocol is suitable for devices with limited computational resources and can be deployed in wireless sensor networks. While the protocol requires an a-priori knowledge about the network setup and structure, it guarantees perfect forward secrecy.
We show how to realize two-factor authentication for a Bitcoin wallet employing the two-party ECDSA signature protocol adapted from MacKenzie & Reiter (2004). We also present a prototypic implementation of a Bitcoin wallet that offers both: two-factor authentication and verification over a separate channel. Since we use a smart phone as the second authentication factor, our solution can be used with hardware already available to most users and the user experience is quite similar to the existing online banking authentication methods.
Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an zero-knowledge proof scheme and ring signature based on NTRU for protecting user information in NFC mobile payment systems without directly using private financial information of the user.
์ต๊ทผ ์ค๋งํธ ๊ธฐ๊ธฐ๋ ๊ฒฐ์ , ํ ์ธ์ฟ ํฐ ๋ฑ ๊ฐ์ข ๊ธฐ๋ฅ์ ์ ๊ณตํ๋ ์๋จ์ผ๋ก ์งํ๋๋ฉด์ ํต์ ๊ณผ ๊ธ์ต์ด ์ตํฉ๋ ๋ชจ๋ฐ์ผ NFC ์๋น์ค์ ์์ฅ์ด ๊ธ์ฑ์ฅํ ๊ฒ์ผ๋ก ์ ๋ง๋๊ณ ์๋ค. ํนํ ๋ชจ๋ฐ์ผ NFC ๊ฒฐ์ ์๋น์ค ์์ฅ์ ํ์ฑํ๊ฐ ์์๋จ์ ๋ฐ๋ผ ๋ชจ๋ฐ์ผ NFC ๊ฒฐ์ ์๋น์ค๋ ๊ตญ๋ด ์ธ์ ์ผ๋ก ๋๋ฆฌ ์ฃผ๋ชฉ๋ฐ๊ณ ์๋ค. ํ์ง๋ง ์ด์ ๋ฐ๋ฅธ NFC ๊ธฐ์ ํ์ฉ ์ฆ๊ฐ๋ก ๊ฐ์ธ์ ๋ณด ์ด์ฉ์ด ๋๋ฉด์ ์นจํด์์ ๋ํ ์ฆ๊ฐํ๊ณ ์๋ค. ์ต๊ทผ ํ๊ตญ์ธํฐ๋ท์งํฅ์์์ ๋ฐํํ "NFC ๊ฐ์ธ์ ๋ณด๋ณดํธ ๋์ฑ ์ต์ข ๋ณด๊ณ ์"์ ๋ฐ๋ฅด๋ฉด ๊ฐ์ธ์ ๋ณด ์ํธํ๋ฅผ ๋ถ๋ถ์ ์ผ๋ก ๋ฏธ์ง์ํ๊ฑฐ๋ ๋ถํ์ํ ๊ฐ์ธ์ ๋ณด์ ๊ณผ๋ํ ์์ง ๋ฐ ์ ์ฅ ๋ฑ์ด ๋ฌธ์ ์ ์ผ๋ก ์ ๊ธฐ๋์์ผ๋ฉฐ Google์ฌ์ Google Wallet ์๋น์ค์ ๊ฐ์ธ์ ๋ณด ์ ์ถ ์ฌ๊ณ ๋ํ ์ด๋ฌํ ๋ฌธ์ ์ ์ ๋ท๋ฐ์นจํ๋ ๊ทผ๊ฑฐ๊ฐ ๋๊ณ ์๋ค. ๋ณธ ๋ ผ๋ฌธ์์๋ ๊ธฐ์กด์ ์๋น์ค๋๊ณ ์๋ NFC ๋ชจ๋ฐ์ผ ๊ฒฐ์ ์๋น์ค ์์์ ๊ฒฐ์ ์ ๋ณด์ ์ด๋ ๊ฒฝ๋ก ๋ณ ๊ฒฐ์ ๊ธฐ์ ์ ์ํ์ ๋ถ์ํ๊ณ OTA(Over the Air) ์์์ ์์ ํ ์ ๋ณด๊ตํ์ ์ํ NTRU ๊ธฐ๋ฐ ์ํธ์ธ์ฆ ๊ธฐ๋ฒ๊ณผ ์ฌ์ฉ์์ ์ํ ๊ฐ์ ๊ฒฐ์ ๋จ๊ณ์์ ๊ฒฐ์ ์ ๋ณด๋ฅผ ์ง์ ์ ์ผ๋ก ์ฌ์ฉํ์ง ์๊ณ ๊ฒฐ์ ์๋ฅผ ์ฆ๋ช ํ ์ ์๋ NTRU๊ธฐ๋ฐ ์์ง์ ์ฆ๋ช ๊ธฐ๋ฒ์ ๋ํด ์ ์ํ๋ค. Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication (NFC) mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an mutual authentication scheme based on NTRU for secure channel in OTA and an zero-knowledge proof scheme NTRU based on for protecting user information in NFC mobile payment systems without directly using private financial information of the user.
Cloud computing is one of the fastest growing segments of IT industry since the users commitments for investment and costs are in relation to usage.The goal of cloud computing is to apply traditional supercomputing or high performance computing power, normally used by military and research facilities to perform tens of trillions of computations per second, in consumer oriented applications such as social networks, financial portfolios, to deliver personalized information, to provide data storage or to power large immersive computer games. Social networks in cloud are used to reflect real world relationships that allow users to share information and form connections between one another, essentially creating dynamic Virtual Organizations. It can be used to share/store data and information within a community ranging from low level computation or storage through high level mash-ups such as photo storage. Anonymous authentication is a technique enabling users to prove the privilege without disclosing real identities. Many existing anonymous authentication protocols assume absolute trust to the cloud provider where all private keys are stored. This trust result in serious security and privacy issues in cloud provider. In the proposed work secure and efficient anonymous mutual authentication protocol using Radio Frequency Identification (RFID) technology for cloud services are implemented based on zkp technique. Zero Knowledge Proof (ZKP) is an interactive system where one party wants to prove its identity to a second party using a password but does not want the second party to learn anything about the password. A mandatory access control (MAC) mechanism is to enforce confidentiality and integrity between a large numbers of users by providing a set of standard questions within a group. Finally present experimental results and validate the acceptable performance impact of our deployment on a modern social network.
Katz and Vaikuntanathan recently improved smooth projective hash functions in order to build oneround password-authenticated key exchange protocols (PAKE). To achieve security in the UC framework they allowed the simulator to extract the hashing key, which required simulation-sound non-interactive zero-knowledge proofs that are unfortunately inefficient. We improve the way the latter extractability is obtained by introducing the notion of trapdoor smooth projective hash function (TSPHF). A TSPHF is an SPHF with a trapdoor, which may not allow to recover the complete hashing key, but which still allows to compute the hash value, which is enough for an application to PAKE with UC-security against static corruptions. We additionally show that TSPHFs yield zero-knowledge proofs in two flows, with straight-line extractability. Besides those quite interesting applications of TSPHF, we also show how to generically build them on languages of ciphertexts, using any ElGamal-like encryption. Our concrete instantiations lead to efficient one-round UC-secure PAKE, extractable zero-knowledge arguments, and verifiable encryption of Waters signatures. In the case of the PAKE, our construction is the most efficient one-round UC-secure PAKE to date.
For various services, OTP (One-Time Password) is increasingly employed to sign in services. The most popular OTP scheme is S/KEY. However, S/KEY scheme is vulnerable to hash collision. In order to solve this problem, Choi and Kim proposed an OTP scheme based on pairing operation. This scheme overcame hash collision problem. Unfortunately, the scheme is vulnerable against insider attack. In this paper, we propose insider attack-resistant OTP scheme based on pairing operation. Our scheme employed zero-knowledge proof to generate OTP values. In short, our scheme sends an OTP and two random numbers encoded with XOR; any adversary has no sense about the random numbers. Our scheme authenticates entities with an OTP and gain a hint on next OTP value from one of random numbers. Consequently, we present insider attack-resistant OTP scheme by eliminating shared parameter among insider (e.g. time stamp).
We consider a class of two-party function evaluation protocols in which the parties are allowed to<br/>use ideal functionalities as well as a set of powerful primitives, namely commitments, homomorphic<br/>encryption, and certain zero-knowledge proofs. We illustrate that with these it is possible to capture<br/>protocols for oblivious transfer, coin- ipping, and generation of multiplication-triple.<br/>We show how any protocol in our class can be compiled to a symbolic representation expressed<br/>as a process in an abstract process calculus, and prove a general computational soundness theorem<br/>implying that if the protocol realises a given ideal functionality in the symbolic setting, then the<br/>original version also realises the ideal functionality in the standard computational UC setting. In<br/>other words, the theorem allows us to transfer a proof in the abstract symbolic setting to a proof in<br/>the standard UC model.<br/>Finally, we show that the symbolic interpretation is simple enough in a number of cases for the<br/>symbolic proof to be partly automated using ProVerif
Lattice-based cryptography is one of the most active research topics in cryptography in recent years. In many cryptographic constructions based on lattice assumptions, the building block is a proof of knowledge of a solution to an instance of the Inhomogeneous Small Integer Solution (ISIS) problem. However, all known such proof \n \nsystems have relatively weak security guarantees: Breaking each of these protocols is potentially easier than solving the underlying instance of the ISIS problem. As a consequence, cryptographic constructions relying on these proof systems typically inherit the sub-optimal security guarantees. Therefore, proof systems with stronger security guarantees are highly desirable. Such protocols are not only interesting from a theoretical point of view, but they also lead to lattice-based cryptographic constructions relying on weaker hardness assumptions than the contemporary schemes. \n \n \n \nIn this thesis, we construct a series of zero-knowledge proofs of knowledge with strong security guarantees and reasonable communication costs, that can find various applications in lattice-based cryptography. Our constructions rely on a simple, yet versatile and effective technique, called Decomposition-Extension. When adapting this technique to the Stern-KTX proof system (Stern โ96 - Kawachi, Tanaka, Xagawa โ08), we obtain a zero-knowledge proof of knowledge for the ISIS problem (in the infinity norm) with a very strong security guarantee: Breaking the protocol is as least as hard as solving the underlying ISIS instance. We then develop our technique to design the following lattice-based cryptographic constructions: \n \n \n \n- Efficient zero-knowledge proofs of plaintext knowledge with strong security guarantees \n \nfor 4 encryption schemes based on the Learning with Errors problem: Regevโs scheme (Regev โ05); the Dual-Regev scheme (Gentry, Peikert, Vaikuntanathan โ08); the PVW scheme (Peikert, Vaikuntanathan, Waters โ08); and the GHV scheme (Gentry, Halevi, Vaikuntanathan โ10). Our results immediately yield 4 lattice-based interactive encryption protocols that are secure under chosen ciphertext attacks. Previously, only zero-knowledge proofs of plaintext knowledge for Regevโs scheme were known, and they are relatively inefficient with rather weak security guarantees. \n \n \n \n- A lattice-based identity-based identification scheme relying on a weaker hardness assumption than in the previous works. Furthermore, we introduce an identity-based ring identification scheme based on the worst-case hardness of lattice problems. To the best of our knowledge, this is the first such scheme. \n \n \n \n- An improved lattice-based group signature scheme relying on relatively weak hardness assumptions, in which the signature size is logarithmic in the number of group users. Earlier lattice-based group signature schemes, which were published before 2013, rely on relatively weak hardness assumptions but have the undesirable property that the size of the signature is linear in the number of group users. A recent scheme (Laguillaumie, Langlois, Libert, Stehlรฉ โ13) achieves logarithmic signature size but it has to rely on relatively strong hardness assumptions. Our construction, thus, simultaneously achieves the good features of the existing schemes.
Abstract Password-authenticated key exchange (PAKE) protocols allow two players to agree on a shared high entropy secret key, that depends on their own passwords only. Following the Gennaro and Lindellโs approach, with a new kind of smooth-projective hash functions (SPHFs), Katz and Vaikuntanathan recently came up with the first concrete one-round PAKE protocols, where the two players just have to send simultaneous flows to each other. The first one is secure in the Bellare-Pointcheval-Rogaway (BPR) model and the second one in the Canettiโs UC framework, but at the cost of simulation-sound non-interactive zero-knowledge (SS-NIZK) proofs (one for the BPR-secure protocol and two for the UC-secure one), which make the overall constructions not really efficient. This paper follows their path with, first, a new efficient instantiation of SPHF on Cramer-Shoup ciphertexts, which allows to get rid of the SS-NIZK proof and leads to the design of the most efficient one-round PAKE known so far, in the BPR model, and in addition without pairings. In the UC framework, the security proof required the simulator to be able to extract the hashing key of the SPHF, hence the additional SS-NIZK proof. We improve the way the latter extractability is obtained by introducing the notion of trapdoor smooth projective hash functions (TSPHFs). Our concrete instantiation leads to the most efficient one-round PAKE UC-secure against static corruptions to date. We additionally show how these SPHFs and TSPHFs can be used for blind signatures and zero-knowledge proofs with straight-line extractability. 1
Zero-knowledge proofs are proofs that are both convincing and yet yield nothing beyond the validity of the assertion being proved. Their direct applications in cryptography are numerous, where they are typically used to force malicious parties to behave according to a predetermined protocol. In addition, zero-knowledge proofs serve as an excellent bench-mark for the study of various problems regarding cryptographic protocols.
Abstract. Groth-Sahai proofs are efficient non-interactive zero-knowledge proofs that have found widespread use in pairingbased cryptography. We propose efficiency improvements of Groth-Sahai proofs in the SXDH setting, which is the one that yields the most efficient non-interactive zero-knowledge proofs. โ We replace some of the commitments with ElGamal encryptions, which reduces the proverโs computation and for some types of equations reduces the proof size. โ Groth-Sahai proofs are zero-knowledge when no public elements are paired to each other. We observe that they are also zero-knowledge when base elements for the groups are paired to public constants. โ The proverโs computation can be reduced by letting her pick her own common reference string. By giving a proof she has picked a valid common reference string this does not compromise soundness. โ We define a type-based commit-and-prove scheme, which allows commitments to be reused in many different proofs.