Message:

<p>[QUOTE=&quot;Sunbird, post: 7993662, member: 116324&quot;]That&#039;s not how security features work. They have to be known to be useful. You can&#039;t authenticate a coin if you can&#039;t observe the security features... If they&#039;re invisible, they have definitely <i><b>not</b></i> served their purpose – they&#039;d be useless in that case, and the mint would be upbraided for its stupidity, by Congress, the media, the public, etc.</p><p><br /></p><p>The goal is to have security features that can be easily used to authenticate, but are not easy to forge. It&#039;s not that hard, since the technology used to authenticate can be very different from the technology used to manufacture or forge. There&#039;s probably a fruitful body of research possible here to formalize the theoretical foundations of this kind of physical security, the nature of the technology split between authentication and manufacturing, etc. I wonder if anyone has done this.</p><p><br /></p><p>This is why the <b>US Currency Education Program</b> exists, where they lay out all the security features of US banknotes, up close and interactively on their website: <a href="https://www.uscurrency.gov/denominations/20" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.uscurrency.gov/denominations/20" rel="nofollow">https://www.uscurrency.gov/denominations/20</a></p><p>And why the Aussie and Swiss central banks have released smartphone apps to help people authenticate their banknotes. Security features have to be publicly known. One of the many things that makes US banknotes terrible are the chaotic and obscure security features that vary from one denomination to the next. Hardly anyone knows what the security features are for any denomination, or looks for them, which makes them useless.</p><p><br /></p><p>It&#039;s structurally similar to encryption and hashing, where you have data or messages that can be easily decrypted with the key, but cannot generally be decrypted without the key, and where the original message cannot be retrieved from the hash output. Here it&#039;s more about being able to use cheap optical tools to authenticate, but, needing much more expensive tooling to manufacture coins with those optical effects, or needing tooling that may not be available at all.[/QUOTE]</p><p><br /></p>

Your name or email address:

Do you already have an account?

• No, create an account now.
• Yes, my password is:
• Forgot your password?

Stay logged in