RANDOMNESS IDENTIFICATION VIA XOR REPOSITION IN LFSR A5/1'S SECOND BLOCK

INTERNATIONAL JOURNAL ON ADVANCED TECHNOLOGY, ENGINEERING, AND INFORMATION SYSTEM (IJATEIS) RANDOMNESS IDENTIFICATION VIA XOR REPOSITION IN LFSR A5/1'S SECOND BLOCK Jorghie Theodore Pallangan1, Alz Danny Wowor2* 1,2 Faculty of Information Technology, Satya Wacana Christian University, Salatiga, Central Java, Indonesia E-mail: 2) Abstract This study designs a random number generation method using the LFSR approach with the A5/1 scheme on three feedback functions. XOR is used as an operation in determining the value of the new bit output against the next iteration of the feedback function. Runs Test, Mono Bit, and Block bit, are used as test materials in producing random output against an input. The use of three feedback functions is used in testing, compared to previous studies that produce random numbers. In the plaintext and ciphertext encryption tests, it shows a "Very Small" correlation level with an average value approaching 0. The use of the LFSR A5/1 scheme with three XOR functions produces random output and can be used for Stream Cipher. Keywords: Linear Feedback Shift Register, Cryptography, A5/1 Schematic 1. INTRODUCTION Cryptography is a necessary algorithm and is often used in securing in-formation. Assurance of security in information can affect the level of user trust in using the algorithm or application. A good algorithm will certainly take into account the complexity of time and space, so that the encryption-decryption process can be optimal. The optimum level of a cryptographic algorithm can be started by paying attention to the key generation process, in which it can accept arbitrary inputs and can produce random outputs, so that in the encryption process, the ciphertext can hide important information from the plaintext (Wowor & Susanto, 2023). Linear feedback shift registers (LFSRs) can generate a key to randomness. By shifting the input bit, exclusive-or (XOR) is used as the determinant of the maximum period random bit (Herman, 2022). Input bits can be used as generators against the entire bit of the sliding register or feedback function. LFSR with A5/1 scheme is one of the optimal algorithms in generating random bit externals. The chart of the complete LFSR A5/1 scheme is given in Figure 1. Figure 1. A5/1 Algorithm Design IJATEIS | VOLUME 3 NO. 4 (2024) https://ojs.transpublika.com/index.php/IJATEIS/ E-ISSN: 2828-5425 564 INTERNATIONAL JOURNAL ON ADVANCED TECHNOLOGY, ENGINEERING, AND INFORMATION SYSTEM (IJATEIS) VOLUME 3 NO. 4 (2024) The A5/1 scheme uses three blocks, where each block has an XOR function process as feedback to carry out the next iteration process. 1. Each block has a role in generating random bit outputs, as well as the selection of each bit entry in each block. In the studies on the A5/1 scheme, there has been no explanation regarding the selection of a13, a16, a17 and a18 as selected entries in the first block, as well as in the second and third blocks. A2 = A20 ⊕ A21 (1) The study in the current study is to use the bit entry in the second block, or to reposition another bit to produce another A2. Randomness testing is a reference to distinguish each reposition that produces the best randomness value. In addition, encryption testing is also used to test each bit output generated from the repositioning process in A5/1, so a comparison process is carried out to see if there is a better repositioning compared to Equation 1. There are 22-bits in total and 2-bits taken, because the XOR function is subject to commutative law so that the number of 2-bits in different positions will produce the same output. 2. LITERATURE REVIEW 2.1. Previous Research In this study, polynomial functions from previous studies were used to underlie the random number generation test. As in Table 1. Table 1. Related Research No. Author Name Research Title 1 Daurat Sinaga, Chaerul Umam, De Rosal Ignatius Moses Setiadi, Eko Hari Rachmawanto (2018) “Super Encryption Technique Using Column Transposition Based Vigenere Cipher on Digital Image” 2 Gede Aditra Pradnyana, and Ida Bagus Putu Suarma Putra (2018) “Securing Digital Data Files with A Combination Algorithm of Triple Transposition Vigenere Cipher and Huffman Method” Research Problem Time required in the process of Encryption and Description of Digital Image Testing the Triple Transposition Vigenere Cipher Algorithm and the Huffman Method Method Results Methods used in the implementation of the combination of column transposition and vigenere cipher methods to secure text files, The result of the comparison shows that the execution time of the message decryption process is longer for Vigenere cipher compared to Vernam cipher on a grayscale image with a size of 256x256 pixels. Produces a high level of security and can be used for remote health monitoring systems Metode Triple Transposisi Vigenere Cipher dan Metode Huffman IJATEIS | INTERNATIONAL JOURNAL ON ADVANCED TECHNOLOGY, ENGINEERING, AND INFORMATION SYSTEM https://ojs.transpublika.com/index.php/IJATEIS/ E-ISSN: 2828-5425 565 RANDOMNESS IDENTIFICATION VIA REPOSITION IN LFSR A5/1'S SECOND BLOCK Jorghie Theodore Pallangan, Alz Danny Wowor 3 Herdyan Kharisma Putra and Sunny Arief Sudiro (2018) “Triple Transposition and Spread Spectrum as Methods for Steganograph Algorithm Development” XOR Secure data by considering bandwidth usage Metode Triple Transposition Vig`enere Cipher dan metode spread spectrum) Generate a security level that can be used for remote health monitoring systems Research by Sinaga et al. (2018) modified the Shift Row and Mix Column AES operations by looking at the problem of a slow process for processing 1024 bytes of data. The modification process succeeded in producing a better process with 3.45 milliseconds for 1024 bytes, and 2048 bytes required 3-4 milliseconds. The modifications made reduce the process time with an average optimization of 86.143%. Research by Pradnyana and Putra (2018) designed a cryptographic system using genomic encryption and deterministic chaos methods, resulting in a fast and secure algorithm to secure medical device data in real time. Experimental results and encryption analysis show that the proposed algorithm provides a high level of security and can be used for remote health monitoring systems. Putra and Sudiro (2018) uses the transposition process of the Triple Transposition Vigenere Cipher and then compresses it with the Huffman Method. This is done as a solution in securing data by considering the use of small memory bandwidth. The cryptography application was successfully designed and can perform the encryption and decryption process properly. The system testing process uses manual calculations with the system and blackbox testing. 2.2. A5/1 Scheme The A5/1 scheme is used as a security medium against eavesdropping and theft on 2G or GMS networks (Sadkhan & Jawad, 2015). A5/1 is a collection of several LFSRs. With A as the main function of each linear function outp (...truncated)