Frequently asked questions
Clear answers to common questions about public key infrastructure, digital certificates and how online trust is established.
What is public key infrastructure in simple terms?
Public key infrastructure, or PKI, is the system of keys, certificates and authorities that lets people and machines prove who they are online. Each party holds a private key that only they can use and shares a matching public key with everyone else. A trusted authority vouches for the link between a public key and a real identity, which is what makes digital signatures and encrypted connections trustworthy.
What is the difference between a public key and a private key?
A key pair consists of two mathematically linked keys where one can undo what the other does. The private key is kept secret by its owner and is used to create signatures or decrypt messages, while the public key can be shared freely and is used to verify those signatures or encrypt messages to the owner. Security depends entirely on the private key never being exposed.
What is an X.509 digital certificate?
An X.509 certificate is a standard structured file that binds a public key to the identity of its owner, such as a person, server or organisation. It also carries details like the issuer, a validity period and the purposes the key may be used for, all protected by the issuing authority's own signature. Software reads this format to decide whether a presented key really belongs to the claimed identity.
What does a Certifying Authority do?
A Certifying Authority verifies the identity of an applicant and then issues a digital certificate that binds the applicant's public key to that verified identity. It is also responsible for managing the lifecycle of those certificates, including publishing status information so others know when a certificate should no longer be trusted. In India, licensed Certifying Authorities operate under the oversight of the Controller of Certifying Authorities.
Where is PKI used in everyday life?
PKI quietly protects many routine activities, from the padlock that secures your browser connection to the signatures on tax and regulatory filings. It also underpins signed software updates and secure email, so that recipients can confirm both the source and integrity of what they receive. In each case the same idea applies: a trusted certificate links a key to an identity you can rely on.