law: Information Technology Act, 2000
  15. Secure digital signature.- 
  If, by application of a security procedure
  
  agreed to by the parties concerned, it can be verified that a digital
  
  signature, at the time it was affixed, was –
  (a) unique to the subscriber affixing it;
  (b) capable of identifying such subscriber;
  (c) created in a manner or using a means under
  
  the exclusive control of the subscriber and is linked to the electronic record
  
  to which related in such a manner that if the electronic record was altered the
  
  digital signature would be invalidated, then such digital signature shall be
  
  deemed to be a secure digital signature.