The act which transforms ciphertext (i.e. the unintelligible and seeming random form of data that is produced by the cryptographic function of encryption) back into its original plaintext or cleartext form. Ciphertext is produced by a symmetric encryption algorithm when a data set is transformed by the encryption process using a selected key. Ciphertext can converted back into its original form (i.e. plaintext) by performing the decryption process using the same symmetric encryption algorithm and the same key used during the encryption process.