Classic Cryptography   Transpositions   Double Transpositions   Pig-Latin   Grille   Vigenere   Caesar Substitution   Atbash   Playfair   Bifid   Monoalphabetic     Substitution   Pig Pen   Map Cipher   Diagraphic Substitution   Jefferson Cipher   Polybius Chequerboard Key-Based    Encryption Glossary Basic Concepts in Data Encryption: Classic Cryptography Diagraphic Substitution Diagraphic substitution is a slightly more complex way of enciphering plain text letters with two letters found within a matrix. However, the matrix used is actually four matrices. There are two matrices used to identify two plain text letters at a time. The other two matrices are used to identify the corresponding cipher text values. Each individual matrix has all the letters of the alphabet: The dashed line above was drawn to identify letters in the plain text matrices labeled P1 and P2. The letter "H" is identified in P1 and "I" in P2. Thus, the plain text letters spell out the word "HI." The corresponding cipher values can be found in C1 and C2 matrices. In this case, "H" in P1 corresponds to "A" in C1. "I" in P2 corresponds with "T" in C2. Thus, the enciphered letters for "HI" are "AT." To decipher "AT" one simply finds the corresponding plain text value in the same row, opposite plain text matrix. To encipher the message, start by writing out the two letter blocks of the message to form the rectangle for each encipher. After drawing the rectangle for each pair of letters find the corresponding cipher values: Plain text: KE EP WO RK IN GO NY OU RE NC RY PT IO NM ET HO DS Cipher: NC BL YH TA CK HX AH KS TE GM SW HU AK FI UU AI PS Can matrices be made differently than shown above? Brain teaser: What must all matrices have in common? Does the order of letters in a matrix make a difference? Copyright ©1999 ThinkQuest Team 27158 — Developed for ThinkQuest 1999