I'm assuming the OP has an iPad2, and therefore no Siri.
To be clear, you won't find any official guides on our forum related to hacking Siri onto an unsupported device with IOS 6. At best, using Siri on the iPad2 is a grey area, and at worst it falls into the same category as piracy.
In order to operate correctly, valid certificates are required for the device to communicate with Apple's Siri servers.
In the "best" scenario, you will be using certificates from another Siri enabled device which you own and be serving those up from your own proxy server. This is at best, the 'grey area', falling into the same area of moral discussion as enabling tethering on a data plan you already pay for.
At worst, you will be using a 3rd party certificate server, normally in Russia, utilising certificates for devices to which you have no right to use. iPadForums cannot support that at all as per our rules.
Hope that clarifies.