title: How to implement Digital Signature in PHP
body: <p>I have to Implement a digital signature in a certificate which we print as PDF in PHP. </p>
  
  <p>The requirement is like that a authorized person like Registrar or Sub Registrar digitally signs a certificate. The basic idea behind implementing Digital signature is to know that:</p>
  
  <p>1) Is the certificate digitally signed by the Authorized person and who was that authorized person or someone else has created it who dont have the authority.</p>
  
  <p>2) Is there any changes in the certificate after the registrar/Sub-Registrar digitally signed the certificate (To stop forgery).</p>
  
  <p>3) When was the document signed or when were the changes were done.</p>
  
  <p>I have searched a lot on this topic put getting nothing and even not any tutorial which could guide me how to do this. I have never heard about this before but according to requirement I have to do this. So please someone guide me or help me how can I implement this in PHP. The certificate in which I have to implement this is <a href="http://crsdemo.lsipl.com/crs/web/index.php/auth/birthCertificate/view/cert/B/NzU2MjQ%3D" rel="noreferrer">http://crsdemo.lsipl.com/crs/web/index.php/auth/birthCertificate/view/cert/B/NzU2MjQ%3D</a></p>