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Public Key Infrastructure (PKI)

Public Key Infrastructure (PKI) is the foundation for secure communication and digital trust in the online world. It is a system that verifies identities and encrypts data exchange, like a digital passport system.

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Components

PKI relies on several components working together

  • Certificate Authorities (CAs): These are trusted third-party organizations that issue digital certificates. They act like verification authorities, ensuring the legitimacy of entities (people, devices, applications) requesting certificates.
  • Digital Certificates: These are electronic documents that bind a public key to an entity. They contain information like the entity's identity, the public key itself, and a digital signature from a trusted CA. ** Public and Private Keys **: PKI utilizes public-key cryptography. Each entity has a pair of keys—a public key (shared openly) and a private key (kept secret). Data encrypted with a public key can only be decrypted by the corresponding private key, ensuring secure communication.

Process

Creating a Certificate:

  1. Generate Private Key: A private key is created, which is then used to calculate the corresponding public key.
  2. Submit Attributes: The private key owner's attributes are submitted to the Certificate Authority (CA) for verification.
  3. Create Certificate Signing Request (CSR): The public key and owner's attributes are encoded into a CSR, which is then signed by the key owner to prove possession of the private key.
  4. CA Validation: The CA validates the CSR and adds its signature using the CA’s private key.
  5. Issue Certificate: The certificate is now legitimate, allowing secure communication to commence.

Using that Certificate:

  1. An entity (user, device, application) requests a digital certificate from a CA.
  2. The CA verifies the entity's identity through a registration process.
  3. If verification is successful, the CA issues a digital certificate containing the entity's public key and the CA's digital signature.
  4. When two entities want to communicate securely, they exchange their public keys.
  5. One entity encrypts the message with the recipient's public key.
  6. Only the recipient can decrypt the message using their private key, ensuring confidentiality.

Benefits

PKI offers several advantages

  • Authentication: It verifies the identity of communicating parties, preventing impersonation.
  • Encryption: It secures data transmission by encrypting messages with public keys.
  • Non-repudiation: It ensures the sender cannot deny sending a message.
  • Data Integrity: It verifies that data hasn't been tampered with during transmission.

Applications

PKI is widely used in various online activities:

  • Secure websites (HTTPS)
  • E-commerce transactions
  • Online banking
  • Secure email communication
  • Virtual Private Networks (VPNs)

In essence, PKI establishes trust in the digital world by verifying identities and securing communication channels. It's a critical component of online security infrastructure.