I don't see anything in BOL (R2 is here: http://msdn.microsoft.com/en-us/library/bb895327%28v=sql.105%29)

However I don't see any reason why symmetric and asymmetric keys aren't available in Express. I see articles about SSL communications, so I think certificates (or keys) work. I don't have an Express edition to try it out, but if this works, you should be fine.

-- create self signed certificate

create certificate MySalaryCert

ENCRYPTION BY PASSWORD = N'UCan!tBreakThis1'

WITH SUBJECT = 'Sammamish Shipping Records',

EXPIRY_DATE = '20121231';

go