Abstract
In the paper we present an involutional block cipher PP-1, which is a scalable SPN. The cipher has very low memory requirements and uses only simple and fast arithmetic operations. The paper discusses in detail the PP-1 cipher design, including the S-box construction, the permutation and the round key scheduling. The quality of the PP-1 cipher is evaluated with respect to differential and linear cryptanalysis. Its quality is compared to the quality of a comparative algorithm with the same block length, as well as to the quality of the class of balanced Feistel ciphers, and in particular to DES quality.