Gigantic data transfer over networks and internet turned in developing a large number of encryption techniques. As a consequence, in parallel, it gave birth to new plans of attacks. In facet of data security, the algorithms specifically Rijndael (Advanced Encryption Standard-AES), SERPENT and TWOFISH are equally considered to be the best. However, they pay less attention in some cryptographic areas like digital image encryption schemes because of their time consumption inferiority. In this paper, we introduce a time diminishing improved version of SERPENT algorithm depending upon chain ring-based substitution boxes (S-boxes) dealing with 8-bit vector instead of 4-bit. The multiplicative substructures in a chain ring have multiple generators and thus the chain ring based S-boxes improve the algebraic complexity of the cipher. Apart from it, the algorithm is utilized in a digital RGB image encryption application where throughout the chain ring operations are performed. The digital image analyses reveal that the proposed scheme consumes less time (i.e. 8.2 microseconds for encryption and 5.8 microseconds for decryption of a 128-bit block) as compared to the existing prominent RGB image encryption techniques. Furthermore, the investigation on the suggested RGB image encryption scheme it is observed that it has a great resistance against the statistical and the differential attacks.

With the growth of networks, the Internet of Things (IoT) and new cyber attacks pose threats to privacy and security, secure communication is therefore becoming one of the most crucial concerns. For this purpose, symmetric algorithms namel; The Rijndael algorithm, the Serpent algorithm, and the TWOFISH algorithm pay equal attention. In this paper, the TWOFISH algorithm’s mathematical complexity is improved by using substitution boxes (S-boxes) drawn from a multiplicative group of units of chain ring $\sum \nolimits _{i=0}^{7} {u^{i}F_{2}} $ . As these S-boxes have the property of having copious generators, they, therefore, produce a rich algebraic complexity. Moreover, the time complexity of the proposed work is modified by processing the 64-bit block throughout the process and reducing the number of subkeys. To measure the strength of the proposed algorithm, various standard color digital images, with a size of $256\times 256$ , are encrypted and tested. The computation speed of the encryption is compared to the standard TWOFISH algorithm’s speed and found that the newly designed algorithm is quite fast. For security analysis and quality assessment, various statistical tests are performed on the standard encrypted images. The results recommend that the proposed algorithm is a strong candidate for digital image encryption.