An efficient block cipher that uses 16 optimal quasigroups is proposed in this paper. All the 16 optimal quasigroups are created using the 16 optimal S-boxes of 4 × 4 bits with the lowest differential and linearity characteristics. These S-boxes are secure against differential and linear attacks. The new block cipher is implemented in C++, compared its performance with the existing quasigroup based block ciphers, and found that the proposed cipher is more efficient than existing quasigroup based proposals. The proposed cipher is analysed against various attacks, including differential and linear attacks, and we found it to be resistant to these attacks. Also, we evaluated our cipher using various statistical tests of the NIST-STS test suite, and we found it to pass each of these tests. We also established in this study that the randomness of our cipher is almost the same as that of the AES-128.

Stream ciphers that use the XOR-function are vulnerable to known-plaintext and reused-key attacks. To overcome such shortcomings of the existing ciphers, we hereby propose a novel stream cipher based on a quasigroup and a pseudo-random number generator (QG-PRNG). The QG-PRNG is also defined in this paper. Novelty of the proposed cipher is that a keystream once generated can be reused multiple times. The proposed cipher is analysed against various attacks, including reused-key, chosen-ciphertext, chosen-plaintext, and known-plaintext attacks and was found it to be resistant to these attacks. The proposed cipher and QG-PRNG are implemented in C++, and the performance of the proposed cipher is compared with some existing quasigroup-based stream ciphers, finding that the proposed cipher is more efficient than the existing proposals. We also evaluated both the QG-PRNG and the proposed cipher using various statistical tests of the NIST-STS, and we found that both the schemes pass these tests.