Keywords

4.1 DNA Cryptography

DNA cryptography is a promising and rapid emerging field in data security. DNA cryptography may bring forward a new hope for unbreakable algorithms. DNA cryptology combines cryptology and modern biotechnology. To encrypt using DNA, sender generates a DNA encoding table, and receiver generates another table through the same encoding technique and sends a clue to the sender to be able to generate it locally. The plaintext to be encoded is divided into two halves equally. If the plaintext is not even, we insert random padding. One half of the plaintext is converted into DNA sequence using sender-based table, and the other half of the plaintext is converted into DNA sequence using receiver-based table. DNA cryptography is a bio-inspired novel technique used for securing end to end communication, where DNA is used as an information carrier. DNA cryptography is assumed to be unbreakable algorithm [23,24,25,26]. The advantages of DNA computing over traditional computing are as follows [27]:

  • Speed: Conventional computers have been known to perform approximately 108 instructions per second (MIPS). Combining DNA strands has been predicted to make computations equivalent to 109.

  • Storage: DNA stores memory at the rate of 1 bit/nm3, whereas conventional storage media can store 1 bit/1012 nm3.

  • Power Requirements: DNA computing does not require power, while computation is taking place. The chemical reactions that create the building blocks of DNA take place without any external power source.

In a nutshell, DNA computing has the characteristics of high parallelism, large storage capacity, and low-energy consumption [33,34,35]. DNA cryptography has a wide range of applications and can be implemented in various fields like mobile networks, cloud computing, IoT devices, real-time applications, the Internet, and multicast applications to secure plaintext messages, images, videos, servers, etc. [36, 37].

4.1.1 Fundamentals of DNA Computing

DNA means deoxyribonucleic acid formed using four basic nucleic acids, namely, adenine (A), cytosine (C), guanine (G), and thymine (T) as depicted in Fig. 4.1. The pairs as (A, T) and (C, G) complement each other. These alphabets can be easily assigned to binary values (A-00, C-01, G-10, T-11). By these encoding rules, there are 4! = 24 possible encoding methods. However, only eight coding combinations are suitable for the principle of complementarity. Because the binary numbers “0” and “1” are complementary, “00” and “11” and “01” and “10” are also complementary [23, 24].

Fig. 4.1
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Bases of DNA block

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4.1.2 DNA Cryptography Algorithm

DNA encryption can be performed through the following steps:

  • Convert the plaintext message into an ASCII form and then convert it to 8 bits binary coded form (Fig. 4.2).

  • Represent the binary data in the DNA coded form (A-00, C-01, G-10, T-11): convert encode binary information into DNA strands.

  • Apply complementary rule to the sequence (A → C, C → G, G → T, T → A).

  • Convert it back to binary.

  • Generate random key and convert it into DND strands then into binary format. The random key has to be a number between 1 and 256. This random key determines the permutation of the four characters A, T, G, and C. For example, when the random key is 1, there is a table for the conversion of ASCII code to nucleotide sequences, and when it is 2, there is another table and so on.

  • XORing the key with the data.

Fig. 4.2
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ASCII symbols and their corresponding DNA sequence

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DNA decryption is the reverse operation of DNA encryption. The total key space results is approximating to 1023. With such huge key space, the reliability and effectiveness of the algorithm are established as the key associated is quite unpredictable and resistant against brute force attacks. Figure 4.3 shows the results of encryption of an image using DNA cryptography.

Fig. 4.3
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(a) unencrypted image, (b) DNA-based encrypted image

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4.2 Quantum Cryptography

Quantum cryptography uses physics to develop a cryptosystem completely secure against being compromised without the knowledge of the sender or the receiver of the messages. The word quantum itself refers to the most fundamental behavior of the smallest particles of matter and energy. In 1982, Richard Feynman came up with the idea of quantum computer, a computer that uses the effects of quantum mechanics to its advantage. In quantum cryptography, two remote parties can communicate securely by using the laws of quantum physics. Quantum cryptography is different from traditional cryptographic systems in that it relies more on physics, rather than mathematics, as a key aspectof its security model.

4.2.1 Properties of Quantum Information

Quantum cryptography rests on two pillars quantum mechanics [28,29,30,31]:

  • The Heisenberg uncertainty principle: it is not possible to measure the quantum state of any system without disturbing that system. Thus, the polarization of a photon or light particle can only be known at the point when it is measured.

  • The photon polarization principle: how light photons can be oriented or polarized in specific directions. Moreover, a photon filter with the correct polarization can only detect a polarized photon or else the photon will be destroyed.

Quantum computer exploits a kind of massive parallelism that cannot be approached by any classical computer. So, it is faster [17]. Quantum technology is a promising solution to overcome information security risks. Key distribution is one of the most important challenges of cryptography. Quantum cryptography can help in solving this problem. In quantum cryptography information is transmitted by quantum bit, also called qubit, which is actually a single photon particle.

The current methods for breaking RSA are not very effective. One method is to factor the N described by the public key. However, with the magnitude of the primes chosen, factoring takes near-infinite time with current methods and technologies (factoring time grows exponentially with input length in bits). In the present day, RSA cannot be broken. However, theoretically it is vulnerable, if a fast algorithm of semi-prime factoring was discovered. So, quantum computing is a threat for RSA encryption.

For years, quantum computers have just been research, theory, and proposals. D-Wave is one of the companies that are making quantum computers a reality.

A regular bit is a transistor that registers either a high or low voltage, which corresponds to 1 or 0, respectively. A quantum bit is a 2-state quantum. Many things can be used as qubits, such as a photon’s horizontal and vertical polarization or the spin up or spin down of an electron. Qubits also have very important properties [38]:

  • Superposition: this is where a qubit is, while left unobserved, all of its possible states. Once observed, it will collapse into one of the possible states.

  • Entanglement: This is where one qubit’s state is linked to another. When entangled with each other, a change in one of the entangled qubits will change the other instantly.

4.2.2 Quantum Algorithms

The promise of quantum computing is that it will help us solve some of the world’s most complex challenges. Quantum systems will have capabilities that exceed our most powerful supercomputers. The two basic algorithms of quantum cryptography are Shor’s algorithm and the Grover’s algorithm.

4.2.2.1 Grover’s Algorithm

Grover’s algorithm is a quantum algorithm that finds with high probability the unique input to a black box function that produces a particular output value.

4.2.2.2 Shor’s Algorithm

Shor’s algorithm provides a dramatic improvement in the efficiency of factoring large numbers. Thus, Shor’s algorithm can be used to attack RSA encryption and related problems. It solves the following problem: Given an integer N, find its prime factors [39].

4.2.2.3 Quantum Cryptography Algorithm: The BB84 Protocol

The fundamental concept of quantum cryptography is sending secret key in the form of photons through an insecure channel. Binary data (zero and one) is encoded to a quantum state based on physics theories. Quantum cryptography is also well-known as quantum key distribution (QKD) . There are two channels in this system. The first channel is used to transmit the quantum secret key with a single photon. The second channel is a public channel like a telephone line or the Internet used to exchange cryptography protocols. The lasers, specifically diode lasers, in the area of QKD [47, 48].

The BB84 protocol is the historical first protocol for quantum key, whose security is based on the principles of quantum mechanics, making it absolutely safe if there is no noise in the quantum channel. The absence of noise in a given situation assumes that the quantum state of particles does not change along the quantum channel. The BB84 protocol is formulated in the language of individual photons, although it can be applied to other realizations of a qubit.

The essence of the BB84 protocol is that one of the users (Alice) randomly selects a series of bits and a series of bases and then sends a user (Bob) a string of photons each of which encodes one bit from the selected string in the base corresponding to the prime number of that bit. In obtaining a photon, Bob randomly selects the measurement base for each photon and, independently of Alice, analogously interprets the result of his measurement for each photon in two ways, as a zero or one. In accordance with the laws of quantum mechanics and following the measuring of the diagonal photon in a rectangular base, its polarization turns into the horizontal or vertical line and vice versa, with random results. In this way, Bob obtains the results coinciding with the state of the photons sent in about half the cases (50%), that is, when he correctly hits the base.

The next stage of the protocol is realized via a public channel, through which Alice and Bob can openly convey classical information to each other. At this stage, we assume that Eva can listen to the announcements by both parties, but she cannot change them or send notifications instead of them. To begin with, Alice and Bob determine (via a public channel) which photons were successfully obtained by Bob and which of them were measured in the correct base. After that, Alice and Bob have the same bit values encoded in these photons, regardless of the fact that this information has never been established in the open communication channel. In other words, each of these photons carries a bit of random information, which is known only to Alice and Bob and no one else. Information about the photons measured in the wrong base is rejected, so Alice and Bob get the so-called sieved key, which, in the event that Eva did not intercept the information, should be the same for both parties. Suppose Eva is eavesdropping on a quantum channel. Due to the random selection of a rectangular or diagonal base, Eva influences the information in such a way that it changes the bits of the sieved key, which would have to be the same for Alice and Bob if there was no Eve [49].

4.2.3 Quantum Cryptography Challenges

When we compare post-quantum cryptography with the currently used asymmetric algorithms, we find that post-quantum cryptography mostly have larger key and signature sizes and require more operations and memory. Still, they are very practical for everything except perhaps very constrained Internet of Things devices and radio. Some other challenges are summarized below:

  • Expensive: need specialized hardware.

  • Complex.

  • Difficult to implement over long distance.

  • Subjected to decoherence. Qubits can retain their quantum state for a short period of time.

  • Quantum algorithms are mainly probabilistic. This means that in one operation, a quantum computer returns many solutions where only one is the correct.

4.3 Chaotic Cryptography

Embedded systems are the driving force for most technological development in many domains such as automotive and healthcare. An example of embedded system architecture is shown in Fig. 4.4.

Fig. 4.4
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Example of embedded system architecture

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Almost 10% of all embedded system products are counterfeit which leads to huge revenue loss. Several attacks methods have been developed, which made it possible to learn the ROM-based keys. Protecting soft IPs is much more challenging because it can be easily copied and even be sold at lower levels of abstraction [11]. Types of attacks on the hardware/software level can be classified into virus/worms, reverse engineering, fault injection, memory modification (Trojan insertion, bus modification, side channel, and bus probing).

Many strong ciphers have been applied widely, such as DES, AES, and RSA. But most of them cannot be directly used to encrypt real-time embedded systems because their encryption speed is not fast enough and they are computationally intensive. So, in this work we present a fast chaotic-based encryption algorithm which is suitable for real-time embedded systems in terms of performance, area, and power efficiency.

4.3.1 Chaotic Theory

All systems can be basically divided into three types [42]:

  1. 1.

    Deterministic systems: these are systems for which for a given set of conditions the result can be predicted and the output does not vary much with change in initial conditions. Examples are computers.

  2. 2.

    Stochastic/random systems: these systems, which are not as reliable as deterministic systems. Their output can be predicted only for a certain range of values. Examples are genetic algorithms.

  3. 3.

    Chaotic systems: these systems are the most unpredictable of the three systems. Moreover they are very sensitive to initial conditions, and a small change in initial conditions can bring about a great change in its output. Examples of chaotic systems are the solar system, population growth, stock market, and weather.

Chaos is derived from the Greek word “Xαos,” which is meaning a state without predictability or order. A chaotic system is a nonlinear, dynamical, and deterministic system which has high sensitive to initial conditions of the system. Chaos system is deterministic system with small change in input results in enormous change in the output, so the system looks as if it is random and prediction becomes impossible (it looks like a noise). It is like butterfly effect. Due to these properties, chaos theory has been used in cryptography/encryption. In this work, chaotic theory is used for providing security at HW level.

4.3.2 Chaotic Encryption System

The proposed chaotic-based encryption is taken from chaotic interleaving in communication [12,13,14]. Here, we proposed to use the algorithm for IP protection in embedded systems. Chaotic encryption of an N × N square matrix of data can be summarized as follows

  1. 1.

    An N × N square matrix is divided into k vertical rectangles of height N and width ni such that n1 + n2 + … + nk = N.

  2. 2.

    These vertical rectangles are stretched in the horizontal direction and contracted vertically to obtain ni × N horizontal rectangle.

  3. 3.

    These rectangles are stacked such as the left one is put at the bottom and the right one at the top.

  4. 4.

    Each vertical rectangle ni × N is divided into ni boxes of dimensions \( \frac{N}{n_i}\times {n}_i \) containing exactly N points.

  5. 5.

    Each of these boxes is mapped column by column into a row of data items. Inside each rectangle, the scan begins from the bottom left corner toward upper elements.

Figure 4.5 shows an example of chaotic encryption of an (8 × 8) square matrix. The secret key Skey(n1, n2, n3) = (2, 4, 2). The security abstraction levels are shown in Table 4.1. The proposed algorithm is working at the algorithm level.

Fig. 4.5
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An illustrating example of the proposed chaotic map. (a) Raw data 8 bits × 8bits, (b) the chaotic map creation 2 × 4 × 2, (c) the encrypted matrix

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Table 4.1 The security abstraction levels
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To evaluate the resistance against security threats, security analysis of proposed encryption algorithm is done. The system proves to be efficient against different types of attacks. If the matrix size becomes 1024 × 8, then the total key space comes out to be sufficient to resist brute force attacks. Based on the proposed architecture, we can represent the key space as a series:

$$ {\mathrm{Key}}_{\mathrm{space}}=\left(n-1\right).\left(1+\sum \limits_{j=1}^{j=n-2}\sum \limits_{i=1}^{i={2}^{\left(n-j-1\right)}-1}\left({2}^{n-j}-2.j\right)\right) $$
(4.1)

Assuming the key size = 1024 = 210 (n = 10), so: keyspace ≅ 1.575 M.

4.3.3 Hardware Implementation of Chaotic Algorithm

First, the proposed algorithm is implemented in MATLAB for performance evaluation against conventional encryption methods. Then it is implemented using Verilog. The key can be hardwired. Chaotic encryption is a symmetric encryption scheme, since it uses same parameters/MAP for encryption and decryption process. Block diagram of the proposed encryption algorithm is shown in Fig. 4.6. The proposed encryption architecture consists of four sub-modules:

  • FIFO: to store the incoming data.

  • Vector to matrix: as Verilog does not accept 2D matrix as an input or output port (Fig. 4.7).

  • Reshape: applying the chaotic map.

  • Matrix to vector: convert matrix to vector.

Fig. 4.6
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Block diagram of the proposed encryption algorithm

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Fig. 4.7
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Vector to matrix block diagram as Verilog does not accept 2D matrix as an input or output port

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The decryption process is the inverse operation. The architecture of the decryption process is shown in Fig. 4.8.

Fig. 4.8
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Block diagram of the proposed decryption algorithm

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It consists of the following:

  • FIFO: to store the incoming data.

  • Vector to Matrix: as Verilog does not accept 2D matrix as an input or output port.

  • Reshape: applying the chaotic map.

  • Matrix to vector: convert matrix to vector.

4.3.4 Evaluation of the Proposed Algorithm

We synthesized the design over a Xilinx Virtex-6 FPGA as depicted in Fig. 4.9. A direct implementation of the design gave a clock frequency of 400 MHz. The throughput is 3.2 Gbps. Compared to conventional encryption methods, the performance of our proposed method is better. A snapshot of the simulation results is shown in Fig. 4.10 where a back-to-back configuration of the encryption/decryption modules is used to ensure that the decrypted data is the same as the plain data. There is a trade-off between the area/latency/power overhead and the provided level of security. Our proposed algorithm provides a good level of security with low area/power/latency overhead. The area is about 5% of AES area. The power consumption is less than AES. The comparison between our proposed algorithm and AES in terms of decryption time for different file sizes is shown in Table 4.2, where our proposed algorithm shows better and fast performance. Moreover, area, delay, and power overhead for our proposed encryption method are shown in Tables 4.3 and 4.4. The resources used by the encryptor including the total number of lookup tables (LUTs), slice registers, and digital signal processing blocks (DSPs), as well as the throughput obtained, are shown in Table 4.5.

Fig. 4.9
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FPGA evaluation board used to perform the proposed algorithm implementation

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Fig. 4.10
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Simulation results for a back-to-back configuration of the encryption/decryption modules

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Table 4.2 Comparison between our proposed algorithm and AES
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Table 4.3 Area, delay, and power overhead for our proposed encryption method
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Table 4.4 Area, delay, and power overhead for our proposed encryption method
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Table 4.5 Comparison with related work
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4.4 Lightweight Cryptography

Lightweight cryptography works between the trade-offs of security, cost, and performance and is focused at devices and systems on edge. The increase in Internet-connected devices requires to build smarter systems that are secure using low-cost hardware solutions. The symmetric and asymmetric ciphers are essentially a major topic of study in hardware cryptography, each having a different set of applications. Hardware for asymmetric ciphers are more complex than symmetric ones and consume more area on chip and power. For example, in terms of computational complexity, symmetric cipher such as AES algorithm is about 1000 much faster than an optimized elliptic curve cryptography that is an asymmetric algorithm. The Internet of Things (IoT) is one of the most promising research topics in the engineering field. IoT is believed to facilitate the way people live in the near future by distantly connecting objects with each other and establishing communication channels between them. According to Cisco’s Internet of Things Group (IoTG), the number of connected devices is expected to reach 50 billion by 2020. IoT has much potential to revolutionize the industry and everyday life in the near future, but some challenges hinder its advancements such as power consumption and security issues. Without sufficient security and privacy, all the benefits of IoT could prove disadvantageous if misused. Different algorithms have been presented in the literature that meets security requirements. Most of the studies have focused on popular algorithms such as AES, Rijndael, DES, Twofish, RSA, and more. However, IoT low area and power requirements make these algorithms unsuitable [22]. So, more IoT-oriented algorithms have been presented to provide better performance in terms of power and area; those are known as lightweight cryptographic algorithms such as PRESENT, RECTANGLE, SIT, HIGHT, CLEFIA, SPECK, SIMON, and KHUDRA algorithm [1,2,3,4,5,6,7,8,9,10].

4.4.1 PRESENT Algorithm

PRESENT is an ultralow power encryption algorithm that is based on substitution permutation (SP) network. PRESENT has a 64 bit input plaintext and either 80 bit or 128 bit key. PRESENT was standardized by NIST in 2012, which provide the algorithm more credibility in its use [46]. PRESENT is a 31-round operation in which an XOR operation is introduced with round Key Ki. It consists of linear transformation called permutation (Fig. 4.11) and nonlinear transformation called substitution (Fig. 4.12). The substitution and permutation are performed once every round. A new key is generated for each round. Decryption is the inverse of the encryption process [18]. Pseudo-code for PRESENT algorithm is shown in Fig. 4.13. To test the proposed encryption/decryption algorithm, we connect them back to back (Fig. 4.14). The power consumption is about 210 mW which is less power than the related work. Moreover, the overall area is less than the related work. For encryption (Fig. 4.15), there are four main blocks for the PRESENT: AddRoundKey , S-box, P-layer, and key schedule. They are working in the following manner [51, 52].

  • Step1: plaintext and the key are stored in a register.

  • Step2: the plaintext is XORed with the key.

  • Step3: a substitutional step is done to provide the confusion needed.

  • Step4: the data is permuted and stored in the register and the counter is increased by 1 and so on.

Fig. 4.11
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Permutation

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Fig. 4.12
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Substitution

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Fig. 4.13
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Pseudo-code for PRESENT algorithm

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Fig. 4.14
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Back-to-back configuration

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Fig. 4.15
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PRESENT encryption core

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For the decryption core (Fig. 4.16), the overall steps are similar to the ones explained in the case of encryption but with some key differences.

  • The s-box, permutation, and key scheduling units are replaced with their inverse modules.

  • The inverse permutation layer is carried out before the inverse s-box layer.

Fig. 4.16
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PRESENT decryption core

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4.4.2 SIT Algorithm

SIT is a symmetric key block cipher that constitutes of 64 bit key and plaintext. In symmetric key algorithm, the encryption process consists of encryption rounds; each round is based on some mathematical functions to create confusion and diffusion. Increase in number of rounds ensures better security but eventually results in increase in the consumption of constrained energy [21]. The cryptographic algorithms are usually designed to take on an average 10 to 20 rounds to keep the encryption process strong enough that suits the requirement of the system. However the proposed algorithm is restricted to just five rounds only; to further improve the energy efficiency, each encryption round includes mathematical operations that operate on 4 bits of data. To create sufficient confusion and diffusion of data in order to confront the attacks, the algorithm utilizes the Feistel network of substitution diffusion functions [15].

4.4.3 HIGHT Algorithm

High security lightweight (HIGHT) algorithm is based on Feistel network structure instead of SPN. HIGHT operates on a 64 bit block size with 128 bit key size. The algorithm is comprised of 32 rounds, each is based on basic operations such as XOR and addition mod 28 [19].

4.4.4 KHUDRA Algorithm

KHUDRA is an FPGA-oriented lightweight algorithm. It’s optimized for balancing LUTs and registers to minimize the FPGA slices. The algorithm is based on recursive Feistel [20].

4.4.5 CAMELLIA Algorithm

It is somehow similar to the standard AES, as it’s a symmetric key block cipher with a fixed block size of 128 bits and three different key sizes of 128, 192, and 256 bits. Unlike other algorithms that focus on hardware implementation, CAMELLIA was designed for both software and hardware. It can be used for both low-cost and high-speed applications [40].

4.4.6 Attribute-Based Encryption (ABE)

ABE is a type of encryption that provides the IoT network with privacy and security through a policy between the attributes of the users in the system. ABE consists of two types, key policy ABE (KP-ABE) and ciphertext policy ABE (CP-ABE). In CP-ABE, the sender’s data access policy is embedded in the ciphertext, and a recipient’s attributes are associated with its private keys. A sender can decrypt the ciphertext only if the attributes associated with its private key satisfy the access policy embedded in the encrypted data [44, 45].

4.5 Blockchain Cryptography

Blockchain is a distributed database that allows direct transactions between two parties without the need for an authoritative mediator. Blockchain is a way to encapsulate transactions in the form of blocks where blocks are linked through the cryptographic hash, hence forming a chain of blocks (Fig. 4.17). Blockchain is used for integrity as depicted in Fig. 4.18. Blockchain relies on different constituents which serve different purposes. The blockchain consists of a sequence of blocks that are stored on and copied between publicly accessible servers. Each block consists of four fundamental elements: the hash of the preceding block; the data content of the block (i.e., the ledger entries); the nonce that is used to give a particular form to the hash; and the hash of the block. By including the hash of the preceding block, each successive block strengthens the authenticity claim for the preceding block. Blocks early in the chain cannot be modified without modifying all subsequent blocks, or the modification will appear as an inconsistency in the hashes. Similarly, adding the data to the hash makes the data unmodifiable without breaking the consistency of the block sequence. Adding a nonce that is used to impose a signature structure to the hash requires significant work to be performed to generate a new block [41]. Assume an attacker is able to change the data present in the block n. Correspondingly, the hash of the block also changes. But, block n + 1 still contains the old hash of the block n. This makes block n + 1 and all succeeding blocks invalid as they do not have correct hash the previous block. Blockchain technology has become so popular due to the following advantages [43]:

  • Resilience: Blockchain is often replicated architecture. The chain is still operated by most nodes in the event of a massive attack against the system.

  • Time reduction: In the financial industry, blockchain can play a vital role by allowing the quicker settlement of trades as it does not need a lengthy process of verification, settlement, and clearance because a single version of agreed-upon data of the share ledger is available between all stack holders.

  • Reliability: Blockchain certifies and verifies the identities of the interested parties. This removes double records, reduces rates, and accelerates transactions.

  • Unchangeable transactions: By registering transactions in chronological order, blockchain certifies the unalterability of all operations which means when any new block has been added to the chain of ledgers, it cannot be removed or modified.

  • Fraud prevention: The concepts of shared information and consensus prevent possible losses due to fraud or embezzlement. In logistics-based industries, blockchain as a monitoring mechanism acts to reduce costs.

  • Security: Attacking a traditional database is the bringing down of a specific target. With the help of distributed ledger technology, each party holds a copy of the original chain, so the system remains operative, even the large number of other nodes fall.

  • Transparency: Changes to public blockchain are publicly viewable to everyone. This offers greater transparency, and all transactions are immutable.

  • Collaboration: Allows parties to transact directly with each other without the need for mediating third parties.

  • Decentralized: There are standard rules on how every node exchanges the blockchain information. This method ensures that all transactions are validated and all valid transactions are added one by one [50].

Fig. 4.17
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Basic blockchain structure. A block has a hash (fingerprint) which is unique to each block. It identifies a block and all of its contents, and it’s always unique. So once a block is created, any change inside the block will cause the hash to change

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Fig. 4.18
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Blockchain: integrity

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4.5.1 Limitations of Blockchain Technology Can Be Summarized as Follows

  • Higher costs: Nodes seek higher rewards for completing transactions in a business which work on the principle of supply and demand.

  • Slower transactions: Nodes prioritize transactions with higher rewards; backlogs of transactions build up.

  • Smaller ledger: It is not possible to a full copy of the blockchain, potentially which can affect immutability, consensus, etc.

  • Transaction costs and network speed: The transactions cost of Bitcoin is quite high after being touted as “nearly free” for the first few years.

  • Risk of error: There is always a risk of error, as long as the human factor is involved. In case a blockchain serves as a database, all the incoming data has to be of high quality. However, human involvement can quickly resolve the error.

  • Wasteful: Every node that runs the blockchain has to maintain consensus across the blockchain. This offers very low downtime and makes data stored on the blockchain forever unchangeable. However, all this is wasteful, because each node repeats a task to reach consensus.

4.5.2 Prime Number Factorization

The mathematical principle behind prime number factorization is that any number, no matter how large, can be produced by multiplying prime numbers. It’s relatively easy to produce any number using prime numbers. However, it’s vastly more difficult to reverse the process and work out which prime numbers were multiplied to produce a particular value once the numbers become large. This reversal is called prime number factorization (Fig. 4.19). Blockchain cryptography relies on prime number factorization for linking the public and private key. The prime number factors of the public key are what form the private key [16].

Fig. 4.19
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Prime number factors example

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4.5.3 Applications of Blockchain Cryptography

4.5.3.1 Money Transfer

Blockchain is a groundbreaking technology that optimizes the way money is transferred and transactions are processed. While it has been used in many fields since its introduction in 2009, blockchain technology is still most widely used in money transfers and transaction reconciliation.

4.5.3.2 Smart Contract

The new key concepts are smart contracts , small computer programs that “live” in the blockchain. They are free computer programs that execute automatically and check conditions defined earlier like facilitation, verification, or enforcement. It is used as a replacement for traditional contracts.

4.5.3.3 Safety of Food

Food companies implement traceability because they see that the consumers require transparency and credibility. Blockchain’s immutability helps them to prove that the information the different supply chain companies provide is uncorrupted.

4.5.3.4 Cryptocurrency

Bitcoin , the first decentralized cryptocurrency, has gained a large attention since its inception in 2009. Built upon blockchain technology, it has established itself as the leader of cryptocurrencies and shows no signs of slowing down. Instead of being based on traditional trust, the currency is based on cryptographic proof which provides many advantages over traditional payment methods (such as Visa and Mastercard) including high liquidity and lower transaction costs [32]. The blockchain is the technology behind Bitcoin. Bitcoin is the digital token, and blockchain is the ledger that keeps track of who owns the digital tokens. You can’t have Bitcoin without blockchain, but you can have blockchain without Bitcoin.

4.6 Conclusions

This chapter discusses the cutting-edge cryptographic techniques such as quantum cryptography, DNA cryptography, chaotic cryptography, lightweight cryptography, and blockchain cryptography. All these cryptography techniques are promising and rapid emerging fields in data security.