See this link:

http://www.cisco.com/univercd/cc/td/doc/product/multisec/asa_sw/v_70/config/aaa.htm#wp1053066

for information on how to do the SDI authentication.

It also includes what servers to support.

Once you create a aaa-server for the sdi server like below:

aaa-server rsasecure protocol sdi

aaa-server rsasecure host 10.0.0.1

(note you might need to specify extra options)

You will need to tie the secure ID authentication to a tunnel-group.

tunnel-group SDIusers type ipsec-ra

tunnel-group SDIusers general-attributes

authentication-server-group rsasecure