uses. The first commercial network layer encryption device was the Motorola Network Encryption System (NES). The system used the SP3 and KMP protocols defined by the NSA Secure Data Network System (SDNS) and were the direct precursors to IPsec. The NES was built in a three part architecture that used a small cryptographic security kernel to separate the trusted and untrusted network protocol stacks. The SDNS program defined a Message Security Protocol (MSP) that was built on the use X.509 defined certificates. The first NSA hardware built for this application was the BBN Safekeeper. The Message Security Protocol was a successor to the IETF Privacy Enhance Mail (PEM) protocol. The BBN Safekeeper provided a high degree of tamper resistance and was one of the first devices used by commercial PKI companies. Field authentication NSA still supports simple paper encryption and authentication systems for field use such as DRYAD. Public systems NSA has participated in the development of several encryption systems for public use. These include: Suite B – a set of public key algorithm standards based on elliptic curve cryptography. Advanced Encryption Standard (AES) – an encryption algorithm, selected by NIST after a public competition. In 2003, NSA certified AES for Type 1 use in some NSA-approved systems. Secure Hash Algorithm – a widely used family of hash algorithms developed by NSA based on earlier designs by Ron Rivest. Digital Signature Algorithm Data Encryption Standard (DES) Skipjack – the cipher developed for Clipper and finally published in 1998. Clipper chip – a controversial failure that convinced NSA that it was advisable to stay out of the public arena. Security-Enhanced Linux – not strictly an encryption system, but a recognition that in the 21st century, operating system improvements are more vital to information security than better ciphers. The Speck and Simon light-weight Block ciphers, published in 2013. References Sources NSA official site Jerry Proc Crypto machine page Brooke Clarke Crypto machines site Telecommunications Security (TSEC) Nomenclature System A History of U.S. Communications Security; the David G. Boak Lectures, National Security Agency (NSA), Volumes I, 1973, Volumes II 1981, partially released 2008, additional portions declassified October 14, 2015 National Security Agency