Standard Encryption (DES and AES)
DES (1977) was the first public encryption standard; AES (2001) replaced it after an open contest and now protects much of the web's traffic and many chat apps.
Open in the interactive tree →IBM's cipher, based on Horst Feistel's Lucifer, became the US Data Encryption Standard (DES) in 1977 with a 56-bit key; in 1998 the EFF's Deep Crack machine reportedly broke a DES key in 56 hours. NIST then ran an open contest: 15 candidates were announced in 1998, five finalists were tested in public, and in October 2000 the Belgian design Rijndael by Joan Daemen and Vincent Rijmen won; it was published as the Advanced Encryption Standard (AES) in November 2001. TLS, the protocol behind HTTPS, uses a public-key handshake to agree on a key and then encrypts the data itself with a cipher such as AES-GCM, and the Signal messaging protocol recommends AES-256 for its messages.
Prerequisites
- Abstract Algebra (Noether)1921-1931AES scrambles bytes with arithmetic in a finite field.
- Programmable Computer (Zuse Z3)1941Such ciphers scramble data in many rounds, which only machines can do quickly.
- Information Theory1948Shannon's secrecy work defined confusion and diffusion, the aims of block ciphers.
Unlocks
- SSL/TLS Secure Connections1995After the public-key handshake, TLS encrypts the data itself with a symmetric cipher such as AES.
- End-to-End Encrypted Messaging2013-2016Signal's Double Ratchet recommends AES-256 to encrypt the messages themselves.