ing information by transforming it (encrypting it) into an unreadable format, called
 ciphertext. Only those who possess a secret (private) key can decipher (or decrypt) the message into plaintext. [Compute
r and Information Sciences] 
n., [custodians] Persons officially entrusted with guarding and keeping things, such as property, artifacts, or records, or with
custody or guardianship of people, such as prisoners, inmates, or wards. [Arts] 
n.,
 Shorthand for “cryptographic system.” [Computer and Informati