Strategies for    Deciphering Encryption Errors Frequency Ordering Glossary Deciphering Encrypted Data: Frequency Ordering The structure of any language enables cryptanalysts to see patterns that emerge from normal messages. Just by looking at a paragraph of text, one can figure out which letters are most common. In the English language, vowels and spaces are the most frequent characters. A few constants and a few known bigrams (2 letters combination) are more common than others. By recognizing patterns in ciphers one can often guess what the letters are decipher the message. These are letters in English, in order of most comon to least common: E T A, O, N, R, I, S H D, L, F, C, M, U G, Y, P, W, B V, K, X, J, Q, Z Besides letter frequency, knowing the frequency of most likely occurring sequence of letters in the particular language may be proven handy as well. In English language, these are sequences in order from most common to least common:    Bigram of Different letters:    TH, HE, AN, RE, ER, IN, ON, AT, ND, ST, ES, EN, OF, TE    Bigram of Same Letters:    LL, EE, SS, OO, TT, FF, RR, NN, PP, CC, MM, GG    Trigram (from most common to least common):    THE, ING, CON, ENT, ERE, ERS, EVE, FOR, HER, TED, TER, TIO, VER Most frequently occurring words have the following characters:    Initial Letters:    T, A, O, M, H, W, C, I, P, B, E, S    Second Letters    H, O, E, I, A, U, N, R, T    Third Letters    E, S, A, R, N, I    Final Letters    E, T, S, D, N, R, Y, G NOTE: More than 50% of English words end with "E." More than 50% of English words start with T, A, O, S, or W. The method of deciphering encrypted message using this is almost futile against strong cipher used for messages that are encrypted using multi-level encryption using several keys. Copyright ©1999 ThinkQuest Team 27158 — Developed for ThinkQuest 1999