Public Key Infrasturcture (PKI) interview questions.
Public Key Infrastructure (PKI) is a framework that provides secure communication over an insecure network by using cryptographic keys. It enables users to securely exchange data over networks such as the internet, ensuring confidentiality, integrity, authentication, and non-repudiation.
- Certificate Authority (CA): Issues and manages digital certificates.
- Registration Authority (RA): Assists in the certificate enrollment process and validates user identities.
- Certificate Repository: Stores issued certificates.
- Certificate Revocation List (CRL): Contains a list of revoked certificates.
- Public Key Infrastructure (PKI): Software and hardware used to manage certificates and keys.
A digital certificate is a digital document that verifies the identity of the certificate holder and binds a public key to an individual or entity. It contains information such as the certificate holder's name, public key, issuer, and expiration date, all digitally signed by a Certificate Authority.
SSL/TLS (Secure Sockets Layer/Transport Layer Security) protocols use PKI to establish secure connections between clients and servers over the internet. In this process, the server presents its digital certificate to the client, which is then verified against the CA's certificate stored in the client's trust store. If the verification is successful, a secure session is established.
A Certificate Revocation List (CRL) is a list of digital certificates that have been revoked before their scheduled expiration date. The CRL is maintained by the Certificate Authority (CA) and is used by clients to check the validity of certificates before trusting them. Clients periodically download the CRL to ensure they do not trust revoked certificates.
Certificate chaining is the process of validating a digital certificate by verifying its chain of trust. This involves checking if the certificate was issued by a trusted CA, if the issuing CA's certificate is valid and trusted, and so on until the root CA certificate is reached. If each certificate in the chain is valid and trusted, the certificate is considered valid.
Certificate revocation is the process of invalidating a digital certificate before its scheduled expiration date. This can occur due to various reasons, such as compromise of the private key or changes in the certificate holder's status. When a certificate is revoked, it is added to the Certificate Revocation List (CRL) maintained by the Certificate Authority (CA). Clients periodically check the CRL to verify the status of certificates.
- Security: PKI provides a secure framework for exchanging sensitive information over insecure networks.
- Authentication: PKI enables users to verify the identity of communication partners.
- Integrity: PKI ensures that data remains unchanged during transmission.
- Non-repudiation: PKI provides proof of the origin and integrity of transmitted data, preventing parties from denying their actions.
- Scalability: PKI can scale to accommodate a large number of users and devices.
Private keys should be generated securely, stored in a secure location, and protected using strong encryption. Access to private keys should be restricted to authorized personnel, and key management procedures should be followed to ensure their integrity and confidentiality.
- Complexity: PKI implementation can be complex and require specialized knowledge and expertise.
- Cost: PKI infrastructure can be expensive to set up and maintain, especially for small organizations.
- Key Management: Managing and securing private keys can be challenging, especially in large-scale deployments.
- User Acceptance: Users may find PKI authentication procedures cumbersome, leading to resistance to adoption.
- Interoperability: Ensuring interoperability between different PKI systems and standards can be challenging in heterogeneous environments.
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