Digital Signature
What is Digital Signature
A digital signature is equivalent to a handwritten signature in paper. It is an electronic verification of the sender.
A digital signature serves three basic purposes.
- Authentication
- Non-repudiation
- Integrity
How Digital Signature Works
Keep in mind, digital signature is not about encrypting document, just like paper-based signature.
Weakness of Digital Signature
Digital signature lacks authentication! (Anyone can pretend he is Bob.)
Man-in-the-middle attack:
So we need digital certificate!
Digital Certificate
Digital certificates are electronic credentials issued by a trusted third party.
Why Do We Need Digital Certificate
Because digital certificate verifies not only the identity of the owner, but also that the owner owns the public key.
Digital certificate verifies the digital signature is truly signed by the claimed signer.
How SSL Certificate Works
Prerequisites
SSL Certificate Flow
Signed on Trusted Third Party CA (eg. Google CA)
Self-Signed Certificate
