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 ...
Read More
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.
M. A. Akhaee; F. Marvasti
Abstract
This paper investigates digital data hiding schemes. The concept of information hiding will be explained at first, and its traits, requirements, and applications will be described subsequently. In order to design a digital data hiding system, one should first become familiar with the concepts and criteria ...
Read More
This paper investigates digital data hiding schemes. The concept of information hiding will be explained at first, and its traits, requirements, and applications will be described subsequently. In order to design a digital data hiding system, one should first become familiar with the concepts and criteria of information hiding. Having knowledge about the host signal, which may be audio, image, or video and the final receiver, which is Human Auditory System (HAS) or Human Visual System (HVS), is also beneficial. For the speech/audio case, HAS will be briefly reviewed to find out how to make the most of its weaknesses for embedding as much data as possible. The same discussion also holds for the image watermarking. Although several audio and image data hiding schemes have been proposed so far, they can be divided into a few categories. Hence, conventional schemes along with their recently published extensions are introduced. Besides, a general comparison is made among these methods leading researchers/designers to choose the appropriate schemes based on their applications. Regarding the old scenario of the prisoner-warden and the evil intention of the warden to eavesdrop and/or destroy the data that Alice sends to Bob, there are both intentional and unintentional attacks to digital information hiding systems, which have the same effect based on our definition. These attacks can also be considered for testing the performance or benchmarking, of the watermarking algorithm. They are also known as steganalysis methods which will be discussed at the end of the paper.
A. Diyanat; M. A. Akhaee; Sh. Ghaemmaghami
Abstract
The present paper is intended to present a robust multiplicative video watermarking scheme. In this regard, the video signal is segmented into 3-D blocks like cubes, and then, the 3-D wavelet transform is applied to each block. The low frequency components of the wavelet coefficients are then used for ...
Read More
The present paper is intended to present a robust multiplicative video watermarking scheme. In this regard, the video signal is segmented into 3-D blocks like cubes, and then, the 3-D wavelet transform is applied to each block. The low frequency components of the wavelet coefficients are then used for data embedding to make the process robust against both malicious and unintentional attacks. The hidden message is inserted through multiplying/dividing these coefficients by a constant parameter which controls the power of the watermark. The watermark extraction relies on a maximum likelihood-based procedure, observing the distribution of the watermarked coefficients. The performance of the proposed scheme has been verified via simulations and found to be superior to some of the well-known existing video watermarking methods.