A Topspin purchase experience is done via SSL, the leading standard for a secure online transaction. The purchase flow has the SSL icon to denote the purchase is secure.
The reason we can't display an SSL icon in the browser navigation bar is because Topspin integrates into an artist's website as an iframe. This allows each artist to maintain consistent branding, however if you right-click and select "frame info," you'll see you're shopping securely.
Topspin submits to regular audits from a card processing authority and we never store or process customers credit card data. Instead, we use a partner (Global Collect), who specializes in card security.