Encryption -
Caesar Cipher - replace each letter with a another letter an exact number of spaces away
Public-key cryptography -
Public + Private keys .
cryptographic algorithms based on mathematical problems to produce one-way functions
RSA -
Clifford Cocks
A user of RSA creates and then publishes a public key based on two large prime numbers, along with an auxiliary value. The prime numbers must be kept secret. Anyone can use the public key to encrypt a message, but only someone with knowledge of the prime numbers can decode the message.[2] Breaking RSA encryption is known as the RSA problem. Whether it is as difficult as the factoring problem remains an open question. There are currently no published methods to defeat the system if a large enough key is used.
Steganography -
practice of concealing a file, message, image, or video within another file, message, image, or video.
Machine Identification Code -
printer steganography, yellow dots, tracking dots or secret dots, is a digital watermark which certain color laser printers and copiers leave on every single printed page, allowing identification of the device
EURion constellation (also known as Omron rings[1] or doughnuts[2]) is a pattern of symbols incorporated into a number of banknote designs
Trees + Graphs -
Trees -
widely used abstract data type simulating a hierarchical tree structure , with root value and subtrees of children with a parent node - set of linked nodes
Graph -
Abstract Data Type
implement the undirected graph and directed graph concepts
consists of a finite (and possibly mutable) set of vertices (also called nodes or points), together with a set of unordered pairs of these vertices for an undirected graph or a set of ordered pairs for a directed graph. These pairs are known as edges (also called links or lines), and for a directed graph are also known as arrows
Seven Bridges of Königsberg
travelling salesman problem
Dijkstra's algorithm - algorithm for finding the shortest paths between nodes in a graph
Decentralisation- systems split into separate branches , not localised at one place
Peer to Peer -computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the application.