CryptoloCryptologygy

ByByGreg BussGreg BussPat ShieldsPat ShieldsBarry BurkeBarry Burke

What is What is Cryptology?Cryptology?

Cryptology is the study of “secret Cryptology is the study of “secret writing.” Modern cryptology writing.” Modern cryptology combines the studies of computer combines the studies of computer science and mathematics for the science and mathematics for the purpose of encoding information to purpose of encoding information to ensure that data is secure.ensure that data is secure.

Cryptography – from the Greek words kryptos, meaning “hidden”, and graphein, meaning “to write”. Literally secret writing.

Key termsCryptanalysis – also referred to as code breaking, the process of undoing Cryptography

Encryption – converts “plaintext” into an encoded text or a “ciphertext”

Decryption – the reverse of Encryption

Cipher – algorithms used to encrypt and decrypt text

Key – an unknown parameter needed to operate a particular cipher’s algorithms

The HistoryThe History

Devices used throughout Devices used throughout history:history:

Scytale Scytale (fr. Gr. skytale). Spartan message in (transposition) cipher. (fr. Gr. skytale). Spartan message in (transposition) cipher. Originally it described a rod or baton carried as a badge of office. It is still Originally it described a rod or baton carried as a badge of office. It is still used by military officers today. Used as an early enciphering device, a used by military officers today. Used as an early enciphering device, a parchment was wrapped spirally around it, and the text was written-in parchment was wrapped spirally around it, and the text was written-in lengthwise. A similar rod at the receiving end permitted correct lengthwise. A similar rod at the receiving end permitted correct decipherment. The word scytale is now used for the message as well as the decipherment. The word scytale is now used for the message as well as the media.media.

cipher diskcipher disk: an enciphering : an enciphering and deciphering tool and deciphering tool developed in the 15th century developed in the 15th century by Leon Battista Alberti. by Leon Battista Alberti. Rather than constructing a Rather than constructing a table with the regular and table with the regular and cipher alphabets on it, he cipher alphabets on it, he created two circular scales, created two circular scales, one smaller and on a disk that one smaller and on a disk that he mounted concentric to the he mounted concentric to the larger circle. This enabled larger circle. This enabled him to move the two alphabet him to move the two alphabet scales relative to each other. scales relative to each other.

EnigmaEnigma: a portable cipher machine used to encrypt and decrypt secret : a portable cipher machine used to encrypt and decrypt secret messages. messages.

The German military model, the Wehrmacht Enigma, is the version most The German military model, the Wehrmacht Enigma, is the version most commonly discussed. The machine has gained notoriety because Allied commonly discussed. The machine has gained notoriety because Allied cryptologists were able to decrypt a large number of messages that had cryptologists were able to decrypt a large number of messages that had been enciphered on the machine. been enciphered on the machine.

Although the Enigma cipher has cryptographic weaknesses, it was, in Although the Enigma cipher has cryptographic weaknesses, it was, in practice, only their combination with other significant factors which practice, only their combination with other significant factors which allowed code breakers to read messages: mistakes by operators, allowed code breakers to read messages: mistakes by operators, procedural flaws, and the occasional captured machine or codebook. procedural flaws, and the occasional captured machine or codebook.

Basic Letter Basic Letter Substitution Substitution

ProgramProgram

Modern Modern ApplicationsApplications

Symmetric-Key Cryptology

Also known as single-key, private-key, one-key and secret-key

Method of encoding where both the sender and receiver of a message hold the same key which is needed to decode the message, and involving the use of block ciphers and stream ciphers.

Encoding through Block Ciphers – Uses a fixed-length groups of bits, known as a block. Will take a plaintext as an input and using a secret key encode the text, and output ciphertext of the same bit size as the input

Encoding through Stream Ciphers - plaintext digits are encrypted one at a time, with the transformation of successive digits varying during the encryption

Public-key Cryptology

Uses a widely distributed public key used for encoding the message, and a different key, related mathematically to the former, used for decoding which is kept secret

More secure than Symmetric-Key Cryptology because the receivers private decoding key is never made known reducing the chance that it may be copied in transit

The Future of The Future of CryptologyCryptology Quantum mechanics has now provided the foundation to a new

approach to cryptology – quantum cryptology. It has been claimed that quantum cryptology, with the use of quantum computers, can solve many problems that are impossible from the perspective of conventional cryptology.

A quantum computer can instantaneously decipher any code A quantum computer can instantaneously decipher any code written by today’s standards. However, with the introduction of a written by today’s standards. However, with the introduction of a working quantum computer, the enciphered codes will also working quantum computer, the enciphered codes will also become impossible to decode without a key, even by another become impossible to decode without a key, even by another quantum computer.quantum computer.