that corresponds to it in the enciphering alphabet: then proceeding horizontally as if the numbers were written on a single line, we take groups of three numbers, look them up in the deciphering alphabet, and write the result under each column. For example, if the message is aide-toi, le ciel t'aidera, and the group size is 5, then encryption proceeds as follows: a i d e-t o i l e c i e l t'a i d e r a 1 1 1.1 2 3 1 1.1 2 1 1 1.2 1 1 1 1.1 1 3.2 3 1.1 1.2 1 1.2 2.1 1 1.3 2.3 1 3.3 1 1.3 2 2 1 1.3 2 1 1 2.3 2 1 1 3.2 2 1 F M J F V O I S S U F T F P U F E Q Q C In this table the periods delimit the trigrams as they are read horizontally in each group, thus in the first group we have 111 = F, 123 = M, 231 = J, and so on. Notes References Classical ciphers