S-1 block cipher

The S-1 block cipher is a symmetric-key block cipher design developed by the National Security Agency (NSA) as part of a classified project. It was specifically engineered for high-security applications and is designed to operate on data blocks of a fixed size, typically 128 bits, with variable key lengths, often aligned with modern cryptographic standards. The S-1 cipher uses a series of operations such as substitution, permutation, and mixing to transform plaintext into ciphertext.