The ProxySG appliance is SHA-2 ready, may refer to KB article 000022556
on how to generate self sign certificate or CSR.
The following output is of the ciphers supported in SGOS 6.5.x:
Cipher Suite: aes128-sha256 aes256-sha256 aes128-sha aes256-sha dhe-rsa-aes128-sha dhe-rsa-aes256-sha des-cbc3-sha rc4-sha rc4-md5 des-cbc-sha exp-des-cbc-sha exp-rc4-md5 exp-rc2-cbc-md5
SGOS 6.5.x and later support SHA256.
Note: SHA2 gathers 4 kinds of hash function: SHA224, SHA256, SHA384 and SHA512. For more information, refer to http://www.tbs-certificates.co.uk/FAQ/en/sha256.html