Giovanni Porta

Italian scientist Giovanni Porta was born in 1535 and made contributions both to steganography and cryptography. Porta described how to conceal a message within a hard-boiled egg by making an ink from a mixture of one ounce of alum and a pint of vinegar, and then using it to write on the shell. The solution would penetrate the porous shell, and leave a message on the surface of the hardened egg albumen, which can be read only when the shell is removed.

In his book, De Furtivis Literam Notis, he earned himself a place in cryptography's history. Porta classified cryptography into three types:

1. Transposition

2. Substitution by symbol

3. Substitution by another letter

Again Porta's contribution to polyalphabiticity was not particularly great, but he was the first to really bring it out into the open. His contribution helped with the development of cryptography by those who came after him.