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<p>[QUOTE=&quot;Conder101, post: 4615104, member: 66&quot;]&quot;When the chip receives a query signal, it generates a long random number which it combines with the ID number; then encrypts the pair. The encrypted pair is sent out. The PCGS server decrypts the pair and separates them. Then it checks the ID number against its database. It sends back &quot;invalid&quot; if that&#039;s the case. If valid, it sends back &quot;valid&quot; plus grade plus cert. no. and maybe a picture as well.&quot;</p><p>But what if the PCGS got that exact same response say a year later.&nbsp; Wouldn&#039;t still decrypt the response, strip out the random number and then respond to the valid serial number?&nbsp; After all the server can&#039;t know what random number the chip generated.&nbsp; Unless it was the server that generated the random number and sent it to the chip in the initial query.&nbsp; It wasn&#039;t generated by the chip.&nbsp; That would stop or at least slow skimming because the server would not get back the same random number it sent.&nbsp; In that case the key would be in the encryption algorithm</p><p><br /></p><p><br /></p><p>So do the ones in the slabs.</p><p><br /></p><p><br /></p><p>And that last one is important because the chip gets its power to do the encryption and respond back from the radio signal it gets from the reader.&nbsp; It has no internal power source of its own.[/QUOTE]</p><p><br /></p>

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