Morteza Amirmohseni; Sadegh Dorri Nogoorani
Abstract
Smart contracts are applications that are deployed on a blockchain and can be executed through transactions. The code and the state of the smart contracts are persisted on the ledger, and their execution is validated by all blockchain nodes. Smart contracts often hold and manage amounts of cryptocurrency. ...
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Smart contracts are applications that are deployed on a blockchain and can be executed through transactions. The code and the state of the smart contracts are persisted on the ledger, and their execution is validated by all blockchain nodes. Smart contracts often hold and manage amounts of cryptocurrency. Therefore, their code should be secured against attacks. Smart contracts can be secured either by fixing their source/byte code before deployment (offline) or by inserting some protection code into the runtime (online). On the one hand, the offline methods do not have enough data for effective protection, and on the other hand, the existing online methods are too costly. In this paper, we propose an online method to complement the offline methods with a low overhead. Our protections are categorized into multiple \emph{safety guards}. These guards are implemented in the blockchain nodes (clients), and require some parameters to be set in the constructor to be activated. After deployment, the configured guards protect the contract and revert suspicious transactions. We have implemented our proposed safety guards by small changes to the Hyperledger Besu Ethereum client. Our evaluations show that our implementation is effective in preventing the corresponding attacks, and has low execution overhead.
Habibullah Yajam; Mohammad Ali Akhaee
Abstract
The future of the IoT requires new methods of payment that can handle millions of transactions per second. IOTA cryptocurrency aims at providing such a solution. It uses a consensus algorithm based on directed acyclic graphs (DAG) that is called Tangle. A tip selection algorithm (TSA) is a part of Tangle ...
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The future of the IoT requires new methods of payment that can handle millions of transactions per second. IOTA cryptocurrency aims at providing such a solution. It uses a consensus algorithm based on directed acyclic graphs (DAG) that is called Tangle. A tip selection algorithm (TSA) is a part of Tangle that determine which unconfirmed blocks (tips) should be confirmed by new blocks. There is always a chance that a small number of valid blocks never get confirmed and become stale. If a significant part of blocks become stale, the Tangle is considered unstable. In this paper, we mathematically prove that a TSA is stable in all transaction rates if and only if the probability of selecting all tips is at least $1/2n$ in which $n$ is the total number of tips. Accordingly, we demonstrate that the MCMC TSA used in IOTA would not be stable in high transaction rates.
Omid Torki; Maede Ashouri-Talouki; Mojtaba Mahdavi
Abstract
Steganography is a solution for covert communication and blockchain is a p2p network for data transmission, so the benefits of blockchain can be used in steganography. In this paper, we discuss the advantages of blockchain in steganography, which include the ability to embed hidden data without manual ...
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Steganography is a solution for covert communication and blockchain is a p2p network for data transmission, so the benefits of blockchain can be used in steganography. In this paper, we discuss the advantages of blockchain in steganography, which include the ability to embed hidden data without manual change in the original data, as well as the readiness of the blockchain platform for data transmission and storage. By reviewing the previous four steganography schemes in blockchain, we have examined their drawback and shown that most of them are non-practical schemes for steganography in blockchain. We have proposed two algorithms for steganography in blockchain, the first one is a high-capacity algorithm for the key and the steganography algorithm exchange and switching, and the second one is a medium-capacity algorithm for embedding hidden data. The proposed method is a general method for steganography in each blockchain, and we investigate how it can be implemented in two most popular blockchains, Bitcoin and Ethereum. Experimental result shows the efficiency and practicality of proposed method in terms of execution time, latency and steganography fee. Finally, we have explained the challenges of steganography in blockchain from the steganographers' and steganalyzers' point of view.
Seyed Salar Ghazi; Haleh Amintoosi; Sahar Pilevar Moakhar
Abstract
In recent years, blockchain technology has been used in many fields, including IoT and Smartphones. Since most of these devices are battery constrained and have low processing capabilities, conventional blockchains are not suitable for these types of systems. In this field, critical challenges that need ...
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In recent years, blockchain technology has been used in many fields, including IoT and Smartphones. Since most of these devices are battery constrained and have low processing capabilities, conventional blockchains are not suitable for these types of systems. In this field, critical challenges that need to be addressed are providing security for transactions and power consumption. An available solution to meet the mentioned challenges is TrustChain. Unlike conventional blockchains, TrustChain does not have a single global chain. Instead, each node is responsible for building and maintaining its local chain.With all the benefits, TrustChain is vulnerable to the whitewashing attack and suffers from client vulnerability issues. Moreover, once a fatal error occurs, the recovery time of each TrustChain node is considerably high. In this paper, wepropose a solution to address the attacks mentioned above by implementing an authentication system with MongoDB on top of TrustChain. Moreover, we connected TrustChain to the distributed cloud storage to significantly reduce the recovery time of nodes in fatal errors (up to 80%). Finally, we evaluate improved TrustChain with the PoW-based smartphone-oriented blockchains from two aspects of security and power consumption, proving that improved TrustChain does not significantly affect the lifetime of the smartphone battery. Its power consumption is less than mentioned blockchains and is more securethan these systems against main attacks.