Nik Azura Nik AbdullahLiyana Chew Nizam ChewAbdul Alif ZakariaKamaruzzaman SemanNorita Md Norwawi2024-05-282024-05-282015--2279-0764https://www.ijcit.com/archives/volume4/issue6/Paper040603.pdfhttps://oarep.usim.edu.my/handle/123456789/5181Volume 04 Issue 06 (page:867-875)In this research paper, we present and compare the randomness analysis conducted towards LBlock block cipher and its modified version namely Modified LBlock. Among the important requirement when designing a block cipher algorithm is that the algorithm can act as a random number generator. Therefore, the aim of performing modification towards LBlock algorithm is to enhance its randomness results. Modification were made by replacing the eight 4 X 4 S-boxes with four different 16 X 16 S-boxes which has the same security strength as S-box of AES. During experimentation, this research project considers a full rounds of LBlock and Modified LBlock algorithms which both algorithms accepts a 64-bit plaintext, utilizes an 80-bit key, executes in 32 rounds and produces a 64-bit ciphertext. Nine different data categories were used to generate inputs (plaintext and key), with each having 100 samples. Blocks of ciphertext were generated from these algorithms and were concatenated to construct a binary sequence. NIST Statistical Test Suite consisting of sixteen tests was used to conduct testing and analysis, and the significance level was set to 1%. From the comparative analysis done, it is concluded that the randomness analysis results for Modified LBlock block cipher has 42.96% improvement compared to its original design when tested under 1% significance level and using the same samples.en-USLBlock Block Cipher, Data Categories, NIST, significance level, randomnessArticle86787546