What is SHA-2?
SHA-2 (“Secure Hash Algorithm #2”) is the most secure hash algorithm NIST currently supports in its FIPS validated cryptography implementations. SHA-2 is really a collection of four hashes (SHA-224, SHA-256, SHA-384 and SHA-512), all of which are stronger than SHA-1.
Complete SHA-2 implementations in file transfer are still uncommon but becoming more common as time passes.
A “SHA-3” contest to find a future replacement for SHA-2 is currently underway and expected to conclude in 2012.