A Cryptographic Algorithm, or cipher or Encryption Algorithm or Decryption Algorithm, the means of altering data from a readable form (also known as plaintext) to a protected form (also known as ciphertext), and back to the readable form. Changing plaintext to ciphertext is known as Encryption, whereas changing ciphertext to plaintext is known as Decryption.
See also: Encryption Algorithm
Source: https://www.yourdictionary.com/cipher-or-cryptographic-algorithm