The cryptography systems currently used consist of two distinct methods:
These can be used on their own, but are usually combined (such as in PGP for maximum security and speed of communication as will be shown later.
The difference between the two types is dependant on the key. A cypher can be broken down into two distinct parts - the algorithm and the key. For example, from methods seen in the past:
| Cypher | Algorithm | Key |
| Stenography | Hide the code | Where it is hidden |
| Monoalphabetic Substitution | Swap over letters | Which original letter to swap for which code letter |
| Polyalphabetic Substitution | Swap over letters as determined by a keyword | The keyword |
| Enigma | The Enigma machine | The wiring and setup of the scramblers/plug-board |