Polybius cipher is a basic form of encryption invented by the Ancient Greek Historian whose name it bears. It is based on fractionating plaintext characters so they can be represented by a smaller set of symbols. In plain English: all the letters of the alphabet are written in a 5×5 square like the one below:
. . . → Read More: Polybius cipher
Vigenere cipher is an encryption technique consisting of a sequence of Caesar cipher each based on the letters of a secret text called a keyword. This mechanism is classified as polyalphabetic substitution.
In Caesar substitution each letter was shifted a number of positions down the alphabet. For example choosing the secret key to be 5, . . . → Read More: Vigenere cipher
Any site involving sensitive information needs to have some of its pages only accessible via SSL. This is a way to make sure that your page is only available on https, using the predefined variable $_SERVER['HTTPS'] to determine the connection and $_SERVER['SERVER_NAME'] and $_SERVER['REQUEST_URI'] to rebuild the accessed url:
1 2 3 4 5 if($_SERVER[’HTTPS’] . . . → Read More: HTTP or HTTPS, find out if the page is secure in PHP