is believed to be one of the first widespread applications of asymmetric cryptography. It greatly reduced the complex logistics and bookkeeping associated with ensuring each encryption device has the right keys and that all keying material is protected and accounted for. The KSD-64A contains a 64kbit EEPROM chip that can be used to store various types of keying and other information. A new (or zeroized) STU-III must first have a "seed key" installed. This key is shipped from NSA by registered mail or Defense Courier Service. Once the STU-III has its seed key, the user calls a toll-free number at NSA to have the seed key converted into an operational key. A list of compromised keys is downloaded to the STU-III at this time. The operational key is supposed to be renewed at least once a year. The operational key is then split into two components, one of which replaces the information on the KSD-64A, at which point it becomes a Crypto Ignition Key or CIK. When the CIK is removed from the STU-III telephone neither unit is considered classified. Only when the CIK is inserted into the STU-III on which it was created can classified information be received and sent. When a call "goes secure", the two STU-III's create a unique key that will be used to encrypt just the call being placed. Each unit first makes sure that the other is not using a revoked key and if one has a more up-to-date key revocation list, it transmits it to the other. Presumably the revocation lists are protected by a digital signature generated by NSA. While there have been no reports of STU-III encryption being broken, there have been claims that foreign intelligence services can recognize the lines on which STU-IIIs are installed and that un-encrypted calls on these lines, particularly what was said while waiting for the "go secure" command to complete, have provided valuable information. Use Hundreds of thousands of STU-III sets were produced and many were still in use as of 2004. STU-III replaced earlier voice encryption devices, including the KY-3 (1960s), the STU-I (1970) and the STU-II (1975). The STU-II had some 10,000 users. These, in turn, replaced less secure voice scramblers. Unlike earlier systems, the STU-III's encryption electronics are completely contained in the desk set. Further, the reduced bandwidth required by a STU-III permitted it to be used for encrypted voice communications even