<p><span>Bitcoin uses elliptic curve cryptography for its keys and signatures, but the specific secp256k1 curve used is rather unusual. The ECDSA keys used to generate Bitcoin addresses and sign transactions are derived from some specific parameters. Due to this characteristic, several questions come up concerning Satoshi’s choice of this curve rather than that of the NIST standard secp256r1 curve. Former President Dan Brown’s address to Bitcoin users on the Bitcoin talk.org online forum concerning the use of secp256k1 in Bitcoin of SECG showed his surprise to see someone uses SECG secp256k1 instead of secp256r1 of NIST.</span><span>In this article, we will analyze the random secp256r1 curve and the Koblitz Secp256k1 curve (parameters, equation, automorphism…), by giving the strengths and weaknesses of each one of them, in order to justify the choice of Bitcoin’s creator, and then we will tackle the mining using the new graphic cards.</span></p>
Open access
Advanced Steganography and Watermarking Techniques
Blockchain is an innovative application model that integrates distributed data storage, peer-to-peer transmission, consensus mechanisms, digital encryption technology and other computer technologies. It is decentralized, secure, and Information disclosure. In the blockchain, digital encryption technology has a core position. The security of user information and transaction data is a necessary condition for the promotion of blockchain. The development of cryptography technology promotes and restricts the further development of blockchain. This paper outlines the infrastructure of blockchain, including the data layer, network layer, consensus layer, contract layer and application layer. The principles of encryption technology is introduced briefly, such as hash function, asymmetric cryptosystem, digital signature. The application of cryptography in all levels of blockchain is analyzed, including data layer, network layer, consensus layer, etc. It shows that cryptography runs through the whole blockchain system. The existing security problems of blockchain is analyzed, and the future research direction is expected.
Open access
Advanced Steganography and Watermarking Techniques
Klitos Christodoulou, Savvas A. Chatzichristofis, Georgios Ch. Sirakoulis, Panayiotis Christodoulou
Games-of-chance require high-levels of trust between participants that is often uncertain and difficult to enforce. The unique characteristics introduced by the blockchain technology can be leveraged to inform a verifiable but transparent pseudo-random generation process that at the same time eliminates the need of an external trustee service or oracle to guarantee the fair execution of the process. We propose a process that builds on a one-dimensional Cellular Automaton (CA) where the evolution of the CA aligns to the evolution of a blockchain. Given an initial seed defined as the point in time where the evolution of the CA is triggered, the set of transition rules, along with the finite number of evolution steps, any external oracle is able to verify and backtrack (but not predict) the outcome of the process. The effectiveness of the implemented system is confirmed by the use of various statistical testing suites that confirm the existence of a set of statistical properties required to produce sufficient pseudo-random number sequences.
Since Gentry's breakthrough construction of fully homomorphic encryption from lattice-based assumptions (STOC 2009), homomorphic cryptography has attracted a lot of attention. In short, homomorphic cryptography schemes allow performing computation on encrypted data without knowing anything about the underlying plaintext. This branch of cryptography has become increasingly useful in building new protocols and schemes with intriguing security and functionality features. In this thesis, we continue to study the applications of homomorphic cryptography and the lattice-based techniques underlying them in realizing new and enhanced cryptographic primitives. We obtain the following results: -We construct the first noninteractive zero knowledge argument (and proof) system for all of NP from standard lattice assumptions. Noninteractive zero knowledge argument systems have found many applications in enhancing the functionality as well as the security of cryptographic schemes and protocols. Constructing noninteractive zero knowledge arguments from lattice assumption has been a long standing open question. We finally close this problem. -We consider multi-key fully homomorphic encryption (FHE) schemes. Traditional fully homomorphic encryption schemes allow computation on plaintext encrypted under a single key. The notion of multi-key fully homomorphic encryption allows homomorphic computation on data encrypted under different keys. We construct multi-key FHE schemes which are naturally dynamic: ciphertexts under new keys can join even during the homomorphic computation. -Finally, we focus on constrained pseudorandom functions (C-PRFs), which are pseudorandom functions (PRFs) with additional functional capabilities. We propose a new approach for building C-PRFs from lattices, and also significantly enhance the underlying lattice parameters.
Over the last few years, there has been a surge of new cryptographic results, including laconic oblivious transfer [13, 16], (anonymous/ hierarchical) identity-based encryption [9], trapdoor functions [19, 20], chosen-ciphertext security transformations [32, 33], designated-verifier zero-knowledge proofs [30, 34, 37], due to a beautiful framework recently introduced in the works of Cho et al. [13], and Dottling and Garg [14]. The primitive of one-way function with encryption (OWFE) [19, 20] and its relatives (chameleon encryption, one-time signatures with encryption, hinting PRGs, trapdoor hash encryption, batch encryption) [9, 14, 16, 17, 33] have been a centerpiece in all these results.
In this paper, we propose a video surveillance system based on blockchain system. The proposed system consists of a blockchain network with trusted internal managers. The metadata of the video is recorded on the distributed ledger of the blockchain, thereby blocking the possibility of forgery of the data. The proposed architecture encrypts and stores the video, creates a license within the blockchain, and exports the video. Since the decryption key for the video is managed by the private DB of the blockchain, it is not leaked by the internal manager unauthorizedly. In addition, the internal administrator can manage and export videos safely by exporting the license generated in the blockchain to the DRM-applied video player.
Advanced Steganography and Watermarking Techniques
The security of the Bitcoin cryptocurrency system depends on the Koblitz curve secp256k1 combined with the digital signature ECDSA and the hash function SHA-256. In this paper, we show that the security of Bitcoin with ECDSA and secp256k1 is not optimal and present a detailed study of the efficiency of Bitcoin with the digital signature algorithm Ed25519 combined with the twisted Edwards curve CurveEd25519 and the hash function SHA-512. We show that Bitcoin is more secure and more efficient with the digital signature algorithm Ed25519 and the twisted Edwards curve CurveEd25519.
Dec 1, 2018·2018 Joint 10th International Conference on Soft Computing and Intelligent Systems (SCIS) and 19th International Symposium on Advanced Intelligent Systems (ISIS)
Various types of cryptocurrency e.g. BitCoin, Ethereum, Zcash, and more, are broadly accepted and used in many different forms of business but a typical problem that the cryptocurrency users are faced with is the delay of coin transfer. For example, it takes several hours for BitCoin and several minutes for Ethereum. These cryptocurrencies also consume a high quantity of electricity for transaction validation. Even though there currently is a type of cryptocurrencies, Ripple, that can be quickly transferred in 4 seconds but still it is a closed system with an owner, not a public cryptocurrency. Similarly, an algorithm "Proof of Stake" used by new coins that are more energy-saving but several problems are still found including (1) 51% attack, (2) a richer with more coins gains higher rewards, and (3) a problematic node for block validation that is not currently active. This research presents a model of an open cryptocurrency system that is able to transfer a coin within 3 seconds in which an algorithm called "Random-Checkers Proof of Stake" (RCPoS) was proposed to randomly select the inspectors for validation processes which can avoid those three problems of the Proof of Stake.
Blockchain Technology Applications and Security
Chaos-based Image/Signal Encryption
Advanced Steganography and Watermarking Techniques
Aiming at the poor encryption effect existing in the data encryption algorithm of e-commerce platform, and the data lost and distorted easily after encrypting, a data encryption algorithm based on blockchain technology is proposed in this paper. By analyzing the symmetric key algorithm and the public key algorithm, the DES encryption algorithm is described in detail. The two related technologies of digital envelopes and message authentication are analyzed to ensure the accuracy of the data and the one time encryption of the data. Based on this, in order to ensure the effectiveness of encryption, the process of asymmetric encryption algorithm based on chaotic sequence of neural network and asymmetric encryption algorithm based on neural network chaotic attractor are analyzed, and the security is tested. While ensuring the accuracy of data, it improves the effect of data encryption and realizes the encryption of e-commerce platform data, which is to realize data encryption algorithm based on blockchain technology. Experimental results show that the~proposed algorithm can encrypt the data of e-commerce platform, and the encryption process is relatively simple, the encryption effect is better, and the accuracy of the encrypted data is relatively high, which provides a theoretical basis for further research of the subject.
Open access
Chaos-based Image/Signal Encryption
Advanced Steganography and Watermarking Techniques
With the development of Internet technology, transmitting, editing and misusing the digital multimedia bring great challenges in misusing detection for multimedia content protection. In this paper we proposed an artwork image digital rights management scheme for Internet misusing detection based on watermark and blockchain with robustness and high-level security. We embed artwork right information such as author, RightHolder, Date and Location information into the artwork image data. In the scheme, we use image Arnold transform to enhance the security and use image DCT coefficients of middle frequency to embed watermark for robustness. In the transparence of watermark, HVS and Watson models are used to control the watermark strength, which can enhance the invisibility. Once the suspicious image data from Internet are misused and spreading the image data on Internet without authorization, especially the high value artwork image data, we can trace the misuse responsibility by extracting the watermark. And according to the above algorithm, we implemented the scheme as DRMChain based on the consortium blockchain which stored the artwork and DRM information in an un-tampered ledger for decentralized rights confirmation. Large amount of experiments indicate the proposed watermark-based trusted blockchain DRM scheme is secure, robust, and for the protection and misuse detection of image data.
Open access
Advanced Steganography and Watermarking Techniques
End-to-End Encryption (E2EE) is widely used in messaging services to protect the security of messages, and most E2EE systems are implemented by asymmetric encryption. However, most mechanisms of public key distribution rely on centralized servers, which may cause leakage and tampering of messages if centralized servers are compromised. In this paper, we propose a decentralized key distribution protocol based on blockchain to solve this problem, and we call it KeyChain. Blockchain can build transparent systems without centralized servers and inherently resist tampering with high Byzantine fault tolerance, therefore it is employed in KeyChain to store public-key-to-id bindings. In addition, in KeyChain, every modification of the public key will be added to the blockchain, so that tampering behaviors can be traced; for the purpose of implementing Byzantine fault tolerance by a low computation cost, KeyChain employs Delegated Proof of Stake (DPOS) as the consensus mechanism to avoid waste of computing resources. Our experiments results show that KeyChain can distribute public keys within 1.3 seconds and only cost a client 0.262MB hard disk space in 24 hours.