Cryptography Concepts
Definitions
The word cryptography is the contraction of two Greek words, kryptós and graphein
- kryptós means hidden or secret
- graphein means write
Cryptography may be defined as the art, techniques, and science of concealing the data and messages to include secrecies, which protect data and messages from unwanted usages.
Cryptosystem is an implementation of cryptographic techniques to provide information security services (such as confidentiality and integrity).
Cryptanalysis is the science and technique of analyzing and breaking cryptographic algorithms and protocols.
Cryptology is the discipline of cryptography and cryptanalysis combined.
History
- The Scytale Cipher
- The Caesar Cipher
- Jefferson’s Wheel
- Enigma Machine
- Vernam’s Cipher
- Modern Cryptography
Encryption Definitions
Plaintext (or cleartext) is a data either on a storage device or in transit over a communication network.
Ciphertext is data after encryption; it is not readable for human beings or usable by any application, without possession of the decryption key.
- transmitted over an unsecure channel or stored in an unsecure area
Channel is any unsecure means to access the encrypted data.
Cryptographic key is a parameter used by encryption and decryption algorithms. It is the most critical material.
- aka secret key or simply key
- static keys are stored for a long time
- ephemeral keys are used for a limited time
Encryption algorithm is the process of creating a ciphertext.
- aka enciphering
- makes use of a key to scramble the input (i.e. the plaintext), so that the result (i.e. the ciphertext) looks like a noise for any observer who does not know the decryption key
Decryption algorithm is the process of transforming a ciphertext into a plaintext; i.e. it is the reverse process of encryption.
Encryption key is a secret value that is known to the sender.
Decryption key is a value that is known to the receiver.
- The decryption key is related to the encryption key, but it is not always identical to it
Cipher is encryption and decryption algorithms that together form a cipher.
- aka encryption system