Type 4 encryption
In NSA terminology, a Type 4 algorithm is an encryption algorithm that has been registered with NIST but is not a Federal Information Processing Standard (FIPS). Type 4 algorithms may not be used to protect classified information.
Alternatively, many sources use "Type 4" specifically to refer to exportable algorithms — 40-bit keys would be typical — which can be relatively easily broken with even a modest amount of computing power.
See also
Categories: Cryptography