An alphabetic shift code uses a coding alphabet which is a standard alphabet shifted by one or more places to the left or the right [Link]

A code mapping maps each of the characters to a unique code mapping [Link]

Vigenere Code uses a pass phase which is used recursively to shift the characters in the encoded phrase. [Link]

This activity shows the character alphabets used with a Vigenere code. [Link]

Diffie-Hellman is used to pass a secret key between two parties. The following activity can be used to show the principle of Diffie-Hellman. [Link]

Play Hang-the-Man and find the security terms [Link]

Wireless Emulator - Cisco IOS [Link]

Users must always be careful in choosing passwords which are not easy to guess or to crack using password cracking programs. The following gives a simulation of a password cracking program [Link]. A one letter password gives 26 combinations (assuming that only lower case letters are used), a two-letter password gives 26*26 combinations, a three-letter password gives 26*26*26 combinations, and so on.