| 1518 CE Johannes Trithemius writes (but does not publish) Steganographia. He publishes Polygraphia libri sex which introduces the tabula recta. |
| 1533 CE Giovan Batista Belaso writes La cifra del. Sig. Giovan Batista Belaso wherein he discusses using a passphrase as the key for a polyalphabetic substitution cipher. |
| 1563 CE Giambattista della Porta writes De Furtivis Literarum Notis describing the first digraphic substitution cipher. Two letters are represented by a symbol. |
| 1564 CE Bellaso publishes an autokey cipher. |
| 1586 CE Blaise de Vigenère publishes Traicté des chiffres wherein he discusses an autokey cipher invented by him. |
| 1605 CE Sir Francis Bacon writes Proficience and Advancement of Learning Divine and Humane, recommending that ciphers "bee without suspition" and advocating steganography. |
| 1790 CE Thomas Jefferson invents his wheel cipher. A row of wheels are held through their centers by an axle so that each wheel can turn independently. The alphabet is printed on the outside of each wheel in a jumbled sequence. The wheels are rotated to compose the plaintext message along one line. With the wheels in that position, another line of letters is selected (the ciphertext) and sent to the recipient. The recipient, in posession of an identical wheel cipher, rotates the wheels to form the ciphertext message. The plaintext message will then appear on another line. |
| 1792 CE French inventor Claude Chappe demonstrates a practical semaphore system. This system eventually traverses all of France. This is the first practical telecommunications system. |
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