Cryptology

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Cryptology

• By
• Greg Buss
• Pat Shields
• Barry Burke

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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.

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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 ciphers algorithms
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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.

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• 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.

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• 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.

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Basic Letter Substitution Program
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Modern Applications
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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
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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
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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 todays 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.