Abstract: Telephone call identification service that safeguards the privacy of an originating station (calling party), while providing useful identifying information to a destination station (called party), is achieved by an encryption process. The encryption process includes combining the originating number with the telephone number of the destination station to form a message. Thereafter, the message is encrypted using the Data Encryption Standard (DES) or the Rivest, Shamir, Adleman (RSA) encryption algorithm to form ciphertext which is transmitted to the destination station. Using either encryption process, the ciphertext is reversible. A telephone switching office, preferably equipped with an electronic program-controlled switching system, executes the encryption algorithm and safeguards the keys used for encryption and decryption. When reversibility of the ciphertext is deemed to be undesirable, the telephone switching office uses modulo n processing of the ciphertext to render it non-reversible.