In NSA terminology, a Type 4 algorithm is an encryption

Encryption

In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...

 algorithm that has been registered with NIST but is not a Federal Information Processing Standard

Federal Information Processing Standard

A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...

 (FIPS). Type 4 algorithms may not be used to protect classified information

Classified information in the United States

The United States government classification system is currently established under Executive Order 13526, the latest in a long series of executive orders on the topic. Issued by President Barack Obama in 2009, Executive Order 13526 replaced earlier executive orders on the topic and modified the...

.

Alternatively, some sources use "Type 4" specifically to refer to exportable algorithms — once limited to 40-bit keys — which can be relatively easily broken with even a modest amount of computing power.

See also

• Type 1 encryption
  Type 1 encryption
  In cryptography, a Type 1 product is a device or system certified by the National Security Agency for use in cryptographically securing classified U.S...
  
  
• Type 2 encryption
  Type 2 encryption
  In cryptography, Type 2 products are unclassified cryptographic equipment, assemblies, or components, endorsed by the National Security Agency , for use in telecommunications and automated information systems for the protection of national security information.Note: The term refers only to...
  
  
• Type 3 encryption
  Type 3 encryption
  In NSA terminology, a Type 3 product is a device for use with Sensitive, But Unclassified information on non-national security systems. Approved algorithms include DES, Triple DES, and AES .-See also:* Type 1 product* Type 2 product* Type 4 product* NSA Suite B Cryptography* NSA Suite A Cryptography...