much secure triple des variant remains quite popular used across wide range applications atm encryption ref name atm ref e mail privacy ref name opgp ref secure remote access ref name ssh ref many block ciphers designed released considerable variation quality many even designed capable practitioners thoroughly broken feal ref name hac ref name schneierbook ref stream ciphers contrast 'block' type create arbitrarily long stream key material combined plaintext bit bit character character somewhat like one time pad stream cipher output stream
Formal science Computer science Computer security Cryptography