## Computer Security :: Lessons :: Symmetric Cipher Model

### Key Terms

You will need to know the following terms before watching this lecture video:

- Plaintext: The original, unencrypted message or data that is input into an encryption algorithm.
- Encryption Algorithm: The algorithm performs substitutions and transformations on the plaintext to generate the cipertext.
- Secret Key: The second input to the encryption algorithm along with the plaintext. The algorithm produces different ciphertext for the same plaintext depending on the key input.
- Ciphertext: The scrambled message that represents the output from the encryption algorithm. To the human eye it appears to be unintelligible.
- Decryption Algorithm: This is simply the encryption algorithm run in reverse with the ciphertext and secret key as inputs and the plaintext as the output.