Like most people interested in cryptography, I have always been curious about the ciphers NSA uses to protect classified information -- the so-called Type 1 ciphers. I have never found any reliable information on these, outside of a few code names. Therefore I was surprised to find the following paragraph on the Navy's Infosec page which suggests that NSA uses 128-bit keys in newer systems and that older equipment that is still in use employs keys that are shorter. http://infosec.navy.mil/TEXT/PRODUCTS/CRYPTO/kg-40.html >The KG-40A is a mandatory modified version of the older KG-40, which >incorporates variable fill capability. The modification entails >replacement of a printed circuit board (motherboard) and the front >panel assembly. The KG-40A provides enhanced security using an >improved cryptographic algorithm and electronic key capability. >Because the KG-40A key is a standard 128-bit key, it can only be >keyed by the AN/CYZ-10 Data Transfer Device (DTD) or a KOI-18 Common >Fill Device (CFD). It cannot accept key from the KYK-13 Electronic >Transfer Device (ETD) or from the KYX-15 Net Control Device (NCD). >The KG-40A is an UNCLASSIFIED controlled cryptographic item (CCI) >when unkeyed and is interoperable with the KG-40. When the KG-40A is >keyed, classification equals that of the key installed.
