Efficient Quantum-Immune Keyless Signatures with Identity
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On the Efficiency of the Lamport Signature Scheme
Technical Sciences 275 ON THE EFFICIENCY OF THE LAMPORT SIGNATURE SCHEME Daniel ZENTAI Óbuda University, Budapest, Hungary [email protected] ABSTRACT Post-quantum (or quantum-resistant) cryptography refers to a set of cryptographic algorithms that are thought to remain secure even in the world of quantum computers. These algorithms are usually considered to be inefficient because of their big keys, or their running time. However, if quantum computers became a reality, security professionals will not have any other choice, but to use these algorithms. Lamport signature is a hash based one-time digital signature algorithm that is thought to be quantum-resistant. In this paper we will describe some simulation results related to the efficiency of the Lamport signature. KEYWORDS: digital signature, post-quantum cryptography, hash functions 1. Introduction This paper is organized as follows. Although reasonable sized quantum After this introduction, in chapter 2 we computers do not exist yet, post quantum describe some basic concepts and definition cryptography (Bernstein, 2009) became an related to the security of hash functions. important research field recently. Indeed, Also, we describe the Lamport one-time we have to discover the properties of these signature algorithm. In chapter 3 we algorithms before quantum computers expound our simulation results related to become a reality, namely suppose that we the efficiency of the Lamport signature. use the current cryptographic algorithms for The last chapter summarizes our work. x more years, we need y years to change the most widely used algorithms and update 2. Preliminaries our standards, and we need z years to build In this chapter the basic concepts and a quantum-computer. -
Outline One-Time Signatures One-Time Signatures Lamport's
Advanced Security Outline § One-Time Signatures Constructions • Lamport’s signature and Key Management • Improved signature constructions • Merkle-Winternitz Signature § Efficient Authenticators (amortize signature) Class 16 • One-way chains (self-authenticating values) • Chained hashes • Merkle Hash Trees § Applications • Efficient short-lived certificates, S/Key • Untrusted external storage • Stream signatures (Gennaro, Rohatgi) § Zhou & Haas’s key distribution One-Time Signatures One-Time Signatures § Use one -way functions without trapdoor § Challenge: digital signatures expensive § Efficient for signature generation and for generation and verification verification § Caveat: can only use one time § Goal: amortize digital signature § Example: 1-bit one-time signature • P0, P1 are public values (public key) • S0, S1 are private values (private key) S0 P0 S0 S0’ P S1 P1 S1 S1’ Lamport’s One-Time Signature Improved Construction I § Uses 1-bit signature construction to sign multiple bits § Uses 1-bit signature construction to sign multiple bits Sign 0 S0 S0’ S0’’ S0* Private values S0 S0’ S0’’ S0* c0 c0’ c0* P0 P0’ P0’’ P0* … … … Public values P0 P0’ P0’’ P0* p0 p0’ p0* P1 P1’ P1’’ P1* Bit 0 Bit 1 Bit 2 Bit n Bit 0 Bit 1 Bit log(n) Sign 1 S1 S1’ S1’’ S1* Private values Sign message Checksum bits: encode Bit 0 Bit 1 Bit 2 Bit n # of signature bits = 0 1 Improved Construction II Merkle-Winternitz Construction § Intuition: encode sum of checksum chain § Lamport signature has high overhead Signature S0 S1 S2 S3 § Goal: reduce size of public -
A Survey on Post-Quantum Cryptography for Constrained Devices
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 11 (2019) pp. 2608-2615 © Research India Publications. http://www.ripublication.com A Survey on Post-Quantum Cryptography for Constrained Devices Kumar Sekhar Roy and Hemanta Kumar Kalita Abstract Quantum Computer” [1]. Shor’s algorithm can solve integer The rise of Quantum computers in the recent years have given factorization problem as well as discrete logarithm problem a major setback to classical and widely used cryptography used by RSA as well as ECC respectively in polynomial time schemes such as RSA(Rivest-Shamir-Adleman) Algorithm using a sufficiently large Quantum Computer. Thus making the and ECC (Elliptic Curve Cryptography). RSA and ECC use of cryptosystems based on integer factorization problem as depends on integer factorization problem and discrete well as discrete logarithm problem obsolete. This current logarithm problem respectively, which can be easily solved by advances has raised a genuine need for development of Quantum Computers of sufficiently large size running the cryptosystems which could serve as viable replacement for infamous Shor’s Algorithm. Therefore cryptography schemes traditionally used cryptosystems which are vulnerable to which are difficult to solve in both traditional as well as quantum computer based attacks. Since the arrival of IoT, the Quantum Computers need to be evaluated. In our paper we Cyber security scenario has entirely shifted towards security provide a rigorous survey on Post-Quantum Cryptography schemes which are lightweight in terms of computational schemes and emphasize on their applicability to provide complexity, power consumption, memory consumption etc. security in constrained devices. We provide a detailed insight This schemes also need to be secure against all known attacks. -
Executing Large Scale Processes in a Blockchain
The current issue and full text archive of this journal is available on Emerald Insight at: www.emeraldinsight.com/2514-4774.htm JCMS 2,2 Executing large-scale processes in a blockchain Mahalingam Ramkumar Department of Computer Science and Engineering, Mississippi State University, 106 Starkville, Mississippi, USA Received 16 May 2018 Revised 16 May 2018 Abstract Accepted 1 September 2018 Purpose – The purpose of this paper is to examine the blockchain as a trusted computing platform. Understanding the strengths and limitations of this platform is essential to execute large-scale real-world applications in blockchains. Design/methodology/approach – This paper proposes several modifications to conventional blockchain networks to improve the scale and scope of applications. Findings – Simple modifications to cryptographic protocols for constructing blockchain ledgers, and digital signatures for authentication of transactions, are sufficient to realize a scalable blockchain platform. Originality/value – The original contributions of this paper are concrete steps to overcome limitations of current blockchain networks. Keywords Cryptography, Blockchain, Scalability, Transactions, Blockchain networks Paper type Research paper 1. Introduction A blockchain broadcast network (Bozic et al., 2016; Croman et al., 2016; Nakamoto, 2008; Wood, 2014) is a mechanism for creating a distributed, tamper-proof, append-only ledger. Every participant in the broadcast network maintains a copy, or some representation, of the ledger. Ledger entries are made by consensus on the states of a process “executed” on the blockchain. As an example, in the Bitcoin (Nakamoto, 2008) process: (1) Bitcoin transactions transfer Bitcoins from a wallet to one or more other wallets. (2) Bitcoins created by “mining” are added to the miner’s wallet. -
Applications of SKREM-Like Symmetric Key Ciphers
Applications of SKREM-like symmetric key ciphers Mircea-Adrian Digulescu1;2 February 2021 1Individual Researcher, Worldwide 2Formerly: Department of Computer Science, Faculty of Mathematics and Computer Science, University of Bucharest, Romania [email protected], [email protected], [email protected] Abstract In a prior paper we introduced a new symmetric key encryption scheme called Short Key Random Encryption Machine (SKREM), for which we claimed excellent security guarantees. In this paper we present and briey discuss some of its applications outside conventional data encryption. These are Secure Coin Flipping, Cryptographic Hashing, Zero-Leaked-Knowledge Authentication and Autho- rization and a Digital Signature scheme which can be employed on a block-chain. We also briey recap SKREM-like ciphers and the assumptions on which their security are based. The above appli- cations are novel because they do not involve public key cryptography. Furthermore, the security of SKREM-like ciphers is not based on hardness of some algebraic operations, thus not opening them up to specic quantum computing attacks. Keywords: Symmetric Key Encryption, Provable Security, One Time Pad, Zero Knowledge, Cryptographic Commit Protocol, Secure Coin Flipping, Authentication, Authorization, Cryptographic Hash, Digital Signature, Chaos Machine 1 Introduction So far, most encryption schemes able to serve Secure Coin Flipping, Zero-Knowledge Authentication and Digital Signatures, have relied on public key cryptography, which in turn relies on the hardness of prime factorization or some algebraic operation in general. Prime Factorization, in turn, has been shown to be vulnerable to attacks by a quantum computer (see [1]). In [2] we introduced a novel symmetric key encryption scheme, which does not rely on hardness of algebraic operations for its security guarantees. -
Speeding-Up Verification of Digital Signatures Abdul Rahman Taleb, Damien Vergnaud
Speeding-Up Verification of Digital Signatures Abdul Rahman Taleb, Damien Vergnaud To cite this version: Abdul Rahman Taleb, Damien Vergnaud. Speeding-Up Verification of Digital Signatures. Journal of Computer and System Sciences, Elsevier, 2021, 116, pp.22-39. 10.1016/j.jcss.2020.08.005. hal- 02934136 HAL Id: hal-02934136 https://hal.archives-ouvertes.fr/hal-02934136 Submitted on 27 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Speeding-Up Verification of Digital Signatures Abdul Rahman Taleb1, Damien Vergnaud2, Abstract In 2003, Fischlin introduced the concept of progressive verification in cryptog- raphy to relate the error probability of a cryptographic verification procedure to its running time. It ensures that the verifier confidence in the validity of a verification procedure grows with the work it invests in the computation. Le, Kelkar and Kate recently revisited this approach for digital signatures and pro- posed a similar framework under the name of flexible signatures. We propose efficient probabilistic verification procedures for popular signature schemes in which the error probability of a verifier decreases exponentially with the ver- ifier running time. We propose theoretical schemes for the RSA and ECDSA signatures based on some elegant idea proposed by Bernstein in 2000 and some additional tricks. -
Keyless Signature Infrastructure for Digital India's Security
ISSN (Online) 2456 -1304 International Journal of Science, Engineering and Management (IJSEM) Vol 4, Issue 10, October 2019 Keyless Signature Infrastructure for Digital India’s Security [1] Mridul Sharma, [2]Rupali Sharma [1][2] University Institute of Engineering, Rayat Bahra University, Mohali, Punjab, India Abstract— In the making of new Digital India there are lots of threats which are there in the path of this dream. Acts of data breach of AADHAAR and Bank Accounts due to the lack of security in our digital services are common but the world is now, moving towards digital era so to be with the world in this digital transformation we must work on our security enhancement to provide a secure platform to government organisations. To serve the three aspects of security that is confidentiality, integrity, and availability of data we need an infrastructure that ensures all these. The Blockchain-Based KSI is the new technology which will support the government of India to achieve its goal of ensuring secure digital Services. It will help the government in providing strong authentication through digital signatures, and will also give the citizens a trust that their PII data is secure and confidential so that they can use these digital services for their all daily work. On the inspiration from Estonia where all their government services are digital in a way such that every government work from issuing a birth certificate to passport verification all these tasks are done digitally. This paper is made to help India in the implementation of this powerful Infrastructure for the digital governmental services providing ease to people and bureaucrats. -
Keyless Signatures' Infrastructure
Keyless Signatures' Infrastructure: How to Build Global Distributed Hash-Trees Ahto Buldas1;2, Andres Kroonmaa1, and Risto Laanoja1;2 1 GuardTime AS, Tammsaare tee 60, 11316 Tallinn, Estonia. 2 Tallinn University of Technology, Raja 15, 12618 Tallinn, Estonia. Abstract. Keyless Signatures Infrastructure (KSI) is a globally dis- tributed system for providing time-stamping and server-supported digi- tal signature services. Global per-second hash trees are created and their root hash values published. We discuss some service quality issues that arise in practical implementation of the service and present solutions for avoiding single points of failure and guaranteeing a service with reason- able and stable delay. Guardtime AS has been operating a KSI Infras- tructure for 5 years. We summarize how the KSI Infrastructure is built, and the lessons learned during the operational period of the service. 1 Introduction Keyless signatures are an alternative solution to traditional PKI signatures. The word keyless does not mean that no cryptographic keys are used during the signature creation. Keys are still necessary for authentication, but the signatures can be reliably verified without assuming continued secrecy of the keys. Keyless signatures are not vulnerable to key compromise and hence provide a solution to the long-term validity of digital signatures. The traditional PKI signatures may be protected by timestamps, but as long as the time-stamping technology itself is PKI-based, the problem of key compromise is still not solved completely. Keyless signatures are a solution to this problem. In a keyless signature system, the functions of signer identification and of evidence integrity pro- tection are separated and delegated to cryptographic tools suitable for those functions. -
Block Chain Based KSI for Delivering Governmental Services in Democratic Nations
International Journal of Recent Engineering Research and Development (IJRERD) ISSN: 2455-8761 www.ijrerd.com || Volume 03 – Issue 07 || July 2018 || PP. 15-24 Block chain based KSI for delivering governmental services in democratic nations Vedna Sharma Junior Research Fellow Institute of Technology Management (Defense Research & Development Organization) Landour Cantt. Mussoorie Uttarakhand (India) Abstract: There are various challenges that government organizations are addressing naturally characterized by transparency and security in government records, improved confidentiality and integrity of data, secure transactions and information security. Government has to be choosing the design that best fits for balancing security and central control with the convenience and opportunity of sharing information or data between organizations and individuals. Government Organizations are also investing in digital technologies to support their goals. Significant investment in technology and efforts has yielded great progress in growth, efficiency & demand of organizations. Block chain stands out as a technology in which various organizations see potential to solve these challenges by implementing strong authentication, data encryption and digital signature. Keywords: Blockchain, Digital Signature, Hashing, public key Infrastructure, Keyless Signature Infrastructure and Governmental Services 1. Introduction Blockchain is decentralized technology that is built on the model of offering security and trust. Blockchain technology have the potential to help governments to collect taxes, deliver benefits, issue passports, record land registries, assure the supply chain of goods and generally ensure the integrity of government records and services. Blockchain technology can simplify the management of trusted information, making it easier for government agencies to access and use critical public-sector data while maintaining the security of this information. -
Secure Signatures and Chosen Ciphertext Security in a Quantum Computing World∗
Secure Signatures and Chosen Ciphertext Security in a Quantum Computing World∗ Dan Boneh Mark Zhandry Stanford University fdabo,[email protected] Abstract We initiate the study of quantum-secure digital signatures and quantum chosen ciphertext security. In the case of signatures, we enhance the standard chosen message query model by allowing the adversary to issue quantum chosen message queries: given a superposition of messages, the adversary receives a superposition of signatures on those messages. Similarly, for encryption, we allow the adversary to issue quantum chosen ciphertext queries: given a superposition of ciphertexts, the adversary receives a superposition of their decryptions. These adversaries model a natural ubiquitous quantum computing environment where end-users sign messages and decrypt ciphertexts on a personal quantum computer. We construct classical systems that remain secure when exposed to such quantum queries. For signatures, we construct two compilers that convert classically secure signatures into signatures secure in the quantum setting and apply these compilers to existing post-quantum signatures. We also show that standard constructions such as Lamport one-time signatures and Merkle signatures remain secure under quantum chosen message attacks, thus giving signatures whose quantum security is based on generic assumptions. For encryption, we define security under quantum chosen ciphertext attacks and present both public-key and symmetric-key constructions. Keywords: Quantum computing, signatures, encryption, quantum security 1 Introduction Recent progress in building quantum computers [IBM12] gives hope for their eventual feasibility. Consequently, there is a growing need for quantum-secure cryptosystems, namely classical systems that remain secure against quantum computers. Post-quantum cryptography generally studies the settings where the adversary is armed with a quantum computer, but users only have classical machines. -
Advanced Trust Services Facilitated by the Industrial-Scale Blockchain Technology
Advanced trust services facilitated by the Industrial-Scale Blockchain technology Risto Laanoja Security Engineer Outline • Guardtime • KSI • What it does • How it works • Trust assumptions • KSI / blockchain applicability in providing eIDAS trusted services • Standardization challenges 2 Advanced trust services facilitated by the Industrial-Scale Blockchain technology 1. Company Overview 3 Advanced trust services facilitated by the Industrial-Scale Blockchain technology Introducing Guardtime Who we are: • Systems engineering company, fundamental and applied research into cryptographic applications • Founded in 2007 in Tallinn, Estonia • Offices in Amsterdam, Palo Alto, Tallinn and Tartu • 71 people 4 Advanced trust services facilitated by the Industrial-Scale Blockchain technology 2. KSI Technology An Industrial Scale Blockchain 5 Advanced trust services facilitated by the Industrial-Scale Blockchain technology Keyless Signature Infrastructure (KSI): An Industrial Scale Blockchain KSI enables real-time Scalability Settlement time massive-scale data One of the most significant In contrast to the widely distributed integrity validation. challenges with traditional crypto-currency approach, the blockchain approaches is scalability number of participants in KSI The technology – they scale at O(n) complexity i.e. blockchain distributed consensus overcomes two major they grow linearly with the number protocol is limited. By limiting the weaknesses of traditional of transactions. number of participants it becomes possible to achieve consensus In contrast the KSI blockchain blockchains: synchronously, eliminating the need scales at O(t) complexity – it grows for Proof of Work and ensuring linearly with time and independently settlement can occur within one from the number of transactions. second. 6 Advanced trust services facilitated by the Industrial-Scale Blockchain technology KSI Signature The KSI Signature is a Upon verification, KSI Signature piece of meta-data which allows to assert: enables the properties of • Signing time the data to be verified. -
Lecture 17 March 28, 2019
Outline Lamport Signatures Merkle Signatures Passwords CPSC 367: Cryptography and Security Michael J. Fischer Lecture 17 March 28, 2019 CPSC 367, Lecture 17 1/23 Outline Lamport Signatures Merkle Signatures Passwords Lamport One-Time Signatures Merkle Signatures Authentication Using Passwords Authentication problem Passwords authentication schemes CPSC 367, Lecture 17 2/23 Outline Lamport Signatures Merkle Signatures Passwords Lamport One-Time Signatures CPSC 367, Lecture 17 3/23 Outline Lamport Signatures Merkle Signatures Passwords Overview of Lamport signatures Leslie Lamport devised a digital signature scheme based on hash functions rather than on public key cryptography. Its drawback is that each key pair can be used to sign only one message. We describe how Alice uses it to sign a 256-bit message. As wtih other signature schemes, it suffices to sign the hash of the actual message. CPSC 367, Lecture 17 4/23 Outline Lamport Signatures Merkle Signatures Passwords How signing works The private signing key consists of a sequence r = (r 1;:::; r 256) of k k pairs( r0 ; r1 ) of random numbers,1 ≤ k ≤ 256. th Let m be a 256-bit message. Denote by mk the k bit of m. The signature of m is the sequence of numbers s = (s1;:::; s256), where sk = r k : mk k k Thus, one element from the pair( r0 ; r1 ) is used to sign mk , so k k k k s = r0 if mk = 0 and s = r1 if mk = 1. CPSC 367, Lecture 17 5/23 Outline Lamport Signatures Merkle Signatures Passwords How verification works The public verification key consists of the sequence 1 256 k k k k v = (v ;:::; v ) of pairs( v0 ; v1 ), where vj = H(rj ), and H is any one-way function (such as a cryptographically strong hash function).