Sains Malaysiana 52(3)(2023): 1023-1036

http://doi.org/10.17576/jsm-2023-5203-24

Analisis Kerawakan Algoritma Terubah Suai Sifer Blok Ultra-Ringan, SLIM

(Randomness Analysis of the Modified Ultra-Lightweight Block Cipher Algorithm, SLIM)

ISMA NORSHAHILA BINTI MOHAMMAD SHAH^1,2,* & EDDIE SHAHRIL BIN ISMAIL¹

¹Department of Mathematical Sciences, Faculty of Science and Technology,

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Cryptography Development Department, CyberSecurity Malaysia, Menara Cyber Axis, 63000 Cyberjaya, Malaysia

Received 19 August 2022/Accepted: 12 February 2023

Abstrak

Ahli kriptografi giat menjalankan penyelidikan dalam bidang kriptografi ringan untuk mengekalkan keselamatan data dalam peranti sumber terhad seperti teg RFID, peranti perubatan dan penjagaan kesihatan serta rangkaian sensor. Satu daripada algoritma kriptografi ringan yang telah dibangunkan untuk tujuan tersebut ialah algoritma SLIM. SLIM merupakan algoritma sifer blok ultra-ringan khusus digunakan dalam Internet Kesihatan Benda. SLIM adalah sifer blok bersaiz 32-bit berasaskan struktur Feistel. Algoritma SLIM mempunyai keberkesanan penyulitan yang baik, walau bagaimanapun, algoritma ini tidak mempunyai fungsi kabur dan sebaran yang diperlukan oleh sifer blok sebagai satu daripada aspek keselamatan kriptografi yang harus dipatuhi. Oleh itu, bagi memperbaiki fungsi kabur dan sebaran algoritma ini, pengubahsuaian terhadap algoritma penjanaan kekunci algoritma SLIM telah dilakukan. Analisis kerawakan kemudiannya dilakukan bagi menilai kerawakan algoritma SLIM dan SLIM terubah suai dengan menggunakan Suit Ujian Statistik NIST. Sebanyak sembilan kategori data iaitu Strict Key Avalanche, Strict Plaintext Avalanche, Plaintext Ciphertext Correlation, Cipher Block Chaining, Random Plaintext Random Key, Low-Density Key, High-Density Key, Low-Density Plaintext dan High-Density Plaintext telah digunakan untuk menjana 100 jujukan input bagi setiap sampel dalam setiap kategori data. Algoritma SLIM dan SLIM terubah suai menjana blok teks sifer yang kemudiannya digabungkan untuk membentuk jujukan dedua. Berdasarkan hasil kajian perbandingan, keputusan analisis kerawakan algoritma SLIM terubah suai adalah lebih baik daripada algoritma asal berdasarkan aras keertian 1%.

Kata kunci: Algoritma SLIM; analisis kerawakan; kriptografi; sifer blok ringan

Abstract

Academics and cryptography professionals are actively conducting research in the field of lightweight cryptography to maintain data security in limited resource devices such as RFID tags, medical and healthcare devices as well as sensor networks. One of the lightweight algorithms that have been developed is the SLIM algorithm. SLIM is an ultra-lightweight block cipher algorithm intended for use on the Internet of Health Things. SLIM is a 32-bit block cipher based on the Feistel structure. The SLIM algorithm does have good encryption efficacy, but the algorithm lacks the diffusion and confusion properties that a block cipher should provide as one of its cryptographic security aspects. Therefore, in order to improve the diffusion and confusion properties of the algorithm, a modification to the key scheduling algorithm for the SLIM algorithm has been done. Randomness analysis was then performed to assess the randomness of the algorithms using the NIST Statistical Test Suite. A total of nine data categories namely Strict Key Avalanche, Strict Plaintext Avalanche, Plaintext Ciphertext Correlation, Cipher Block Chaining, Random Plaintext Random Key, Low-Density Key, High-Density Key, Low-Density Plaintext, and High-Density Plaintext was used to generate 100 input sequences for each sample in each data category. The algorithms generate ciphertext blocks, which are then combined to form a binary sequence. According to the results of the comparison study, the proposed algorithms’ randomness analysis results are better than the original algorithm based on the 1% significance level.

Keywords: Cryptography; lightweight block cipher; randomness analysis; SLIM algorithm

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^*Corresponding author; email: p111700@siswa.ukm.edu.my