1. Cryptography
   1. From the Greek words
      1. kryptos ("hidden")
      2. graphein ("to write")
   2. The practice and study of hiding the meaning of information, most commonly used to hide the meaning of information in transit.
2. Encryption
   1. Changing information using an algorithm (process) in such a way that only authorized parties can access it and those who are not authorized cannot.
   2. Encrypted information is returned to its original state using decryption.
3. Algorithm
   1. A process to be followed in calculations or problem-solving operations.
   2. Cipher:
      1. A type of algorithm used to perform encryption or decryption.
4. Key
   1. A piece of information that determines the functional output of a cryptographic algorithm.
   2. Encryption:
      1. plaintext to ciphertext
   3. Decryption:
      1. ciphertext to plaintext
   4. Keys also specify transformations in other cryptographic algorithms:
      1. digital signatures (certificates)
      2. message authentication codes (MAC tags)
5. Private Key
   1. A type of key that is known only to a specific user or users who keep the key a secret.
6. Public Key
   1. A type of key that is known to all parties involved in encrypted transactions within a given group.
7. Relationship Between Key & Cipher
   1. A cipher can be thought of as a Lock.
   2. This lock may be in the locked (encrypted) or unlocked (unencrypted) state.
   3. For the locked (enciphered) information to change state, the correct key must be applied.