Certification path validation algorithm

The certification path validation algorithm is the algorithm which verifies that a given certificate path (also called a certificate chain) is valid under a given PKI. A path starts with the Subject certificate and proceeds through a number of intermediate certificates up to a trusted certificate, typically issued by a trusted Certification Authority (CA). Verifying the chain includes checking that each certificate is valied (meaning that it is inside its validity period), that each certificate after the Subject certificate actually