Cryptography

Cryptography, from the Greek word "kryptos" (meaning concealed), involves the concealment of information from third-parties. It is concerned with the first two thirds of the CIA Triad – the confidentiality and integrity of data.

Generally speaking, the field can be split into:

Common Terms

Plain text: Human-legible text. Can be transformed into cipher text via an encryption algorithm.
Clear text: Synonym of "plain text".
Cipher text: Text that has been transformed into an unreadable message via some encryption algorithm.
Encryption: The process of scrambling data or messages, making it unreadable and secret.
Decryption: The opposite of encryption.
Encoding: A means of transforming data from one format to another.
Decoding: The opposite of encoding.
Cryptographic key: A string of bits used by a cryptographic algorithm to transform plain text into cipher text or vice versa.
Symmetric-key encryption: Model of encryption that uses the same shared key for both encryption and decryption.
Asymmetric encryption: Model of encryption that uses the recipient's public key to encrypt a message, and the recipient's private key to decrypt a message.
Block Cipher: An encryption algorithm that operates on a group of bit at once rather than only one bit at a time. Contrast with Stream Cipher.
Stream Cipher: An encryption algorithm that operates on one bit of plaintext at a time. Contrast with Block Cipher.
Hashing algorithm: A one-way function that takes arbitrary input and produces fixed-length output, such that every unique input produces unique output with very high probability.
Hash: The output of a hashing algorithm. Synonym for "digest".
Digest: The output of a hashing algorithm. Synonym for "hash".
Salt: A string appended to a password to create a unique digest when run through a hashing algorithm.
Entropy: The amount of unpredictability in a given ciphertext. Entropy colloquially refers to how close the ciphertext is to ideal randomly generated text.

Relevant Note(s): Information Security