Cyber Security:

Cryptography

Cryptography has been used throughout history. Julius Caesar used simple ciphers to send military orders to his generals, whereas more sophisticated medieval ciphers were used that withstood decryption until the late ninteenth century. More recently there is the famous Enigma codes of the Second World War.

Cryptography is underpinned by mathematics. Letters and numbers have to be manipulated in a reproducible way so that the message can be decrypted by the receiver - reversing the process. There are two types: symmetric and asymmetric.

The recent development of computers has allowed for far more complex means of encryption to be employed than was possible before.

Any data that can be represented in binary format, i.e. using 0s and 1s, can be encrypted by a computer.

Cryptography isn't just used to hide secrets, it can also be used to authenticate data sent on an insecure network – such as the internet. See hashing.

Computers can:

easily perform the necessary mathematical operations

employ more complex mathematics than could be reasonably expected of a human

encrypt and decrypt at a much faster rate than a human

handle complex and long messages - a large amount of data

Common applications for cryptography include:

secure banking and payments systems – cryptography ensures your money is safe when it is transferred between accounts, issued at ATMs or used to shop online

protecting privacy of conversations made over mobile telephones

safeguarding wireless networks that give access to the internet

securing files on hard disks and memory sticks

authenticating electronic documents

electronic voting

securing media files such as music or movies from piracy, where it is known as Digital Rights Management (DRM).

Terminology in cryptography

plaintext – information that can be directly read by humans or a machine. Plaintext is a historic term pre-dating computers, when encryption was only used for hardcopy text, nowadays it is associated with many formats including music, movies and computer programs

ciphertext – the encrypted data

a cipher – the mathematics (or algorithm) responsible for turning plaintext into ciphertext and reverting ciphertext to plaintext. It is sometimes called ‘code’ – there is a technical difference between the two but they are used interchangably except by experts.

encryption – the process of converting plaintext to ciphertext (occasionally you may see it called ‘encipherment’).

decryption – the process of reverting ciphertext to plaintext (occasionally ‘decipherment’).

keys - pieces of information that determine the output from an encryption (or decryption) process.

Pages related to this topic:

Symmetric Cryptography

Asymmetric Cryptography

Cryptography in Action

Cryptography Standards