Example 0.3.3: Caesar was said to have used a cryptosystem in which each letter was replaced with the one three steps forward in the alphabet (wrapping around for X,Y, and Z).a Thus the plaintext MATRIX would be encrypted as the cyphertext PDWULA. The function that maps each plaintext letter to its cyphertext replacement could be written as A )→ D, B )→ E,C )→ F, D )→ G, W )→ Z, X )→ A, Y )→ B,Z )→ C This function’s domain and co-domain are both the alphabet {A, B, . . . , Z}.
