Docstoc

Cryptology

Document Sample
Cryptology Powered By Docstoc
					Cryptology
       By
    Greg Buss
   Pat Shields
   Barry Burke
What is Cryptology?
   Cryptology is the study of “secret writing.”
    Modern cryptology combines the studies of
    computer science and mathematics for the
    purpose of encoding information to ensure that
    data is secure.
                       Key terms
Cryptography – from the Greek words kryptos, meaning “hidden”, and graphein,
meaning “to write”. Literally secret writing.


Cryptanalysis – 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 History
 Devices             used throughout history:
   Scytale (fr. Gr. skytale). Spartan message in (transposition) cipher. 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 parchment was wrapped spirally around it, and the text was written-in
    lengthwise. A similar rod at the receiving end permitted correct decipherment. The word scytale
    is now used for the message as well as the media.
   cipher disk: an enciphering and
    deciphering tool developed in the 15th
    century by Leon Battista Alberti.
    Rather than constructing a table with
    the regular and cipher alphabets on it,
    he created two circular scales, one
    smaller and on a disk that he mounted
    concentric to the larger circle. This
    enabled him to move the two alphabet
    scales relative to each other.
   Enigma: a portable cipher machine used to encrypt and decrypt secret messages.
   The German military model, the Wehrmacht Enigma, is the version most commonly discussed.
    The machine has gained notoriety because Allied cryptologists were able to decrypt a large
    number of messages that had been enciphered on the machine.
   Although the Enigma cipher has cryptographic weaknesses, it was, in practice, only their
    combination with other significant factors which allowed code breakers to read messages:
    mistakes by operators, procedural flaws, and the occasional captured machine or codebook.
   Basic Letter
Substitution Program
Modern Applications
            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 Cryptology
   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 written by today’s
    standards. However, with the introduction of a working quantum computer, the
    enciphered codes will also become impossible to decode without a key, even by
    another quantum computer.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:14
posted:10/6/2012
language:English
pages:11