Substitution Permutation Network

Definition ∞ A Substitution Permutation Network is a cryptographic design that shuffles and replaces data bits to secure information. This is a fundamental architectural design for block ciphers, which iteratively applies a sequence of substitution and permutation operations to encrypt data. Substitution layers, often implemented via S-boxes, provide confusion by obscuring the relationship between plaintext and ciphertext. Permutation layers offer diffusion by spreading the influence of individual plaintext bits across the ciphertext. This combination creates strong cryptographic security.
Context ∞ Substitution Permutation Networks form the basis for many modern symmetric key encryption algorithms used in securing digital asset transactions and blockchain data. Understanding their operational principles is essential for evaluating the underlying security of cryptographic protocols. Ongoing research continues to optimize SPN designs for enhanced performance and resistance against advanced cryptanalytic techniques.