NSA Suite B Cryptography
NSA Suite B Cryptography was a set of cryptographic algorithms promulgated by the National Security Agency as part of its Cryptographic Modernization Program. It was to serve as an interoperable cryptographic base for both unclassified information and most classified information.
Suite B was announced on 16 February 2005. A corresponding set of unpublished algorithms, Suite A, is "used in applications where Suite B may not be appropriate. Both Suite A and Suite B can be used to protect foreign releasable information, US-Only information, and Sensitive Compartmented Information (SCI)."
| Purpose | Algorithm | Standard | Parameter Length | Notes | |
|---|---|---|---|---|---|
| Secret | Top-Secret | ||||
| Symmetric encryption | AES | FIPS 197 | 128 | 256 | For traffic flow, AES should be used with either the Counter Mode (CTR) for low bandwidth traffic or the Galois/Counter Mode (GCM) mode of operation for high bandwidth traffic (see Block cipher modes of operation). |
| Digital Signature | Elliptic Curve Digital Signature Algorithm (ECDSA) | FIPS 186-2 | 256 | 384 | Curves P-256 and P-384, the latter providing 192-bit security. |
| Key agreement | Elliptic-curve Diffie–Hellman (ECDH) | NIST SP 800-56A | 256 | 384 | Same as above. |
| Message digest | SHA-2 | FIPS 180-3 | 256 | 384 | |
In addition, "[d]uring the transition to the use of elliptic curve cryptography in ECDH and ECDSA, DH, DSA and RSA can be used with a 2048-bit modulus to protect classified information up to the SECRET level."
In 2015, NSA replaced Suite B with the Commercial National Security Algorithm Suite (CNSA). The general selection of algorithms types remain unchanged. DSA was removed. DH and RSA were reclassified as "supported" instead of "legacy" with the minimum modulus size raised to 3072 bits. In 2018, the Suite B IETF RFC documents were reclassified as historical.