A code book is a collection of codes that are used to encrypt confidential information. It is also known as a cipher book, codebook, or cipher codebook. The terms cipher, cryptogram, and cryptograph are also often used interchangeably with codebook. The military often uses code books, and they are also used by intelligence agencies, spy agencies, and government departments to safeguard sensitive information. Other potential synonyms for "code book" could include a decryption book, encryption book, hidden book, confidential book, secure book, or covert book. Ultimately, any term that can convey the idea of a collection of codes used to encrypt or decrypt sensitive information could be used as a synonym for "code book".