Randomness Evaluation of the Improved 3D-Playfair (i3D) Cipher Algorithm
Ritchell S. Villafuerte, Ariel M. Sison, Alexander Arcenio Hernandez, Ruji P. Medina · 2020
In cryptography, two things are highly valued to secure the exchange of communication. One is the secrecy of key generated by a cryptographic algorithm, and the other one is its ability to have an unpredictable sequence in the message. The i3D-Playfair is a symmetric block cipher algorithm designed to improve the existing 3D (4×4×4) Playfair cipher algorithm. The improvement focuses on securing the key and likewise enhancing the message encryption. Randomness determines the cryptographic strength of an algorithm. Evaluating the p-value in statistical tests identifies the binary sequence as random or non-random. This paper uses the five selected NIST Statistical Test Suites battery tests to get the probability p-value in determining the randomness of a binary sequence. NIST STS is a standard statistical test for randomness. The selected statistical tests are the following: frequency (monobit) test, frequency test within a block, runs test, the longest run test of 1's in a block, and cumulative sums test. The experimental result shows that all the statistical tests have a passing p-value that is greater than 0.01 (p-value≥ 0.01). Also, the p-value of p-values (POP) of all the statistical tests is greater than or equal to 0.0001, showing uniformity of p-values. The histogram of all the tests also shows that the p-value is normally distributed. Furthermore, results show that all the randomness tests conducted execute an acceptable proportion that is above 57 or was able to achieve a passing percentage above 95%. Thus, the proposed i3D-Playfair algorithm generates random numbers. It is then strongly suggested to implement i3D-Playfair Cipher in software applications and messaging to secure data transmission.