How does Windows Live address the secuity issues of online transactions

E-Commerce needs a secure way for the ecommerce site and the online client to transact.
I am researching the way this is done and how security is provided to the client at the ecommerce site. I appreciate any comments that will address this issue in an understanable way.
So far I understand from reading the Brian Arbocast Press release issued August 12, 2001 how passport began this process of ecommerce becoming secure.
I am aware that a Live ID is now replacing Passport as the Identifier method of securely purchasing online . Is Windows cardspace now available for Internet use?