Blockchain’s vast applications in different industries have drawn several researchers to pursue extensive research in securing blockchain technologies. In recent times we could see several institutions coming together to create consortium based blockchain networks such as Hyperledger. Although for applications of blockchain such as Bitcoin, Litcoin, etc. the majority-attack might not be a great threat but for consortium based blockchain networks where we could see several institutions such as public, private, government, etc. are collaborating, the majority-attack might just prove to be a prevalent threat if collusion among these institutions takes place. This paper proposes a methodology where we can use intelligent software agents to monitor the activity of stakeholders in the blockchain networks to detect anomaly such as collusion, using supervised machine learning algorithm and algorithmic game theory and stop the majority attack from taking place.

This paper presents a new combined symmetric key cryptographic technique, which is generally an amalgamation of Bit Manipulation, generalized Modified Vernam Cipher, Single Bit Manipulation and Modified Caesar Cipher. The technique proposed here is basically an advanced and upgraded module of SD-AREE cryptographic method, which is based on Modified Caesar Cipher along with Bit Manipulation and the SD-AREE module is very useful in excluding any repetition pattern from a message that is to be encrypted. The proposed method, SD-AREE-I Cipher, is a complete cipher method and unlike its predecessor, SD-AREE, does not need to be added to other cryptographic methods to make those methods stronger. SD-AREE-I method is used to encrypt/decrypt different file formats and the results were very satisfactory. This method is unique and strong because the method contains feedback mechanism and generates new encrypted output every time even with slightest change in the input file (message). The proposed method can also be used for network security.

Due to tremendous growth in communication technology, now it is a real problem / challenge to send some confidential data / information through communication network. For this reason, Nath et al. developed several information security systems, combining cryptography and steganography together, and the present method, ASA_QR, is also one of them. In the present paper, the authors present a new steganography algorithm to hide any small encrypted secret message inside QR CodeTM , which is then randomized and then, finally embed that randomized QR Code inside some common image. Quick Response Codes (or QR Codes) are a type of two-dimensional matrix barcodes used for encoding information. It has become very popular recently for its high storage capacity. The present method is ASA_QR is a combination of strong encryption algorithm and data hiding in two stages to make the entire process extremely hard to break. Here, the secret message is encrypted first and hide it in a QR CodeTM and then again that QR CodeTM is embed in a cover file (picture file) in random manner, using the standard method of steganography. In this way the data, which is secured, is almost impossible to be retrieved without knowing the cryptography key, steganography password and the exact unhide method. For encrypting data The authors used a method developed by Nath et al i.e. TTJSA, which is based on generalized modified Vernam Cipher, MSA and NJJSA method; and from the cryptanalysis it is seen that TTJSA is free from any standard cryptographic attacks, like differential attack, plain-text attack or any brute force attack. After encrypting the data using TTJSA,the authors have used standard steganographic method To hide data inside some host file. The present method may be used for sharing secret key, password, digital signature etc.

In this paper the authors present a new integrated symmetric-key cryptographic method, named SJA, which is the combination of advanced Caesar Cipher method, TTJSA method, Bit wise Rotation and Reversal method. The encryption method consists of three basic steps: 1) Encryption Technique using Advanced Caesar Cipher, 2) Encryption Technique using TTJSA Algorithm, and 3) Encryption Technique using Bit wise Rotation and Reversal. TTJSA Algorithm, used in this method, is again a combination of generalized modified Vernam Cipher method, MSA method and NJJSAA method. Nath et al. already developed some symmetric key encryption methods namely MSA, DJSA, DJJSA, modified DJJSA, NJJSA, TTJSA, TTSJA, DJMNA, UES-I, UES-II etc. The cryptanalysis shows that TTJSA is free from standard cryptographic attacks such as differential attack, plain text attack or any brute force attack. In the present method the authors have used advanced modified Caesar Cipher method where the authors have modified the standard Caesar Cipher method and then they applied TTJSA method to make the entire crypto system very hard to break. The present method has been tested on different plain text specially with repeated character and the spectral analysis of the plain text and the encrypted is also been shown. The spectral analysis shows that the present cryptography method, SJA can not be broken with any kind of standard cryptography attack. The authors propose that the present method will be most suitable for password, SMS or any kind of small message encryption.