Higher SSL Encryption

I've been looking around the web at SSL certificates and the highest I've seen has been 168 bit, what is the hightest created and what is the highest available? I've heard about 512 Bit but it doesn't seemed to be used on web sites, 128 Bit appears to be the most commonly used. Is it possible to obtain a 512 Bit SSL certificate?

 

 

 

 

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