What is Substitution?

Understanding Substitution

The process of exchanging one letter or bit for another. In cryptography substitution is a technique where elements of plaintext letters bits or blocks are systematically replaced with different elements according to a defined algorithm and key. This transforms readable data into ciphertext by substituting values rather than rearranging them. Substitution is a fundamental concept in most encryption algorithms. Substitution techniques appear in cryptographic standards like FIPS 197 AES and various algorithm specifications. Organizations implement substitution through established encryption algorithms rather than creating custom substitution ciphers following cryptographic best practices. For example the Advanced Encryption Standard AES uses substitution boxes S-boxes as a core component replacing each byte of data with another value according to a transformation table creating the confusion property essential to strong encryption. Related terms Cryptography Cipher Encryption Confusion S-box Substitution cipher Caesar cipher Permutation.