What is an X.509 Certificate ?

X.509 certificates contains :

  • Subject (entity identity)
  • Subject’s public key
  • Issuer’s name

Verification process

  • The issuer signs the hash of all the certificate data.
  • To verify a certificate :
    • Compute the hash of the data.
    • Check the signature using the issuer’s public key.
  • If I trust the issuer’s public key, I can trust the subject’s public key.