Page "Key size" Paragraph 19

The NSA specifies that " Elliptic Curve Public Key Cryptography using the 256-bit prime modulus elliptic curve as specified in FIPS-186-2 and SHA-256 are appropriate for protecting classified information up to the SECRET level.

Use of the 384-bit prime modulus elliptic curve and SHA-384 are necessary for the protection of TOP SECRET information.