Public Key Infrastructure (PKI)
Public Key Infrastructure (PKI) is a comprehensive framework to create, manage, distribute, use, store, and revoke digital certificates. It plays a crucial role in securing communications and ensuring the integrity and authenticity of data.
PKI consists of several components, such as:
Certificate Authorities (CAs): Trusted entities that give out digital certificates proving the identity of entities like people, organizations, or devices.
Registration Authorities (RAs): Entities that check the identity of people or organizations before a CA provides them a digital certificate.
Digital Certificates: Electronic documents that link a public key to a person or organization’s identity.
Public and Private Keys: Cryptographic keys used to encode and decode data.
Certificate Revocation Lists (CRLs): These are records of digital certificates that have been revoked and shouldn’t be relied on.
As we discussed public key infrastructure (PKI) aims to prove that the owners of public keys are who they say they are.
The keys in PKI are generated through public key cryptography using cryptographic algorithms like RSA or ECC.
PKI is a framework that uses these keys but doesn’t create them.
Before diving deeper into public key infrastructure, let’s first understand symmetric and asymmetric key cryptography.
Symmetric Key Cryptography
Secret-key cryptography also called symmetric key or shared-key cryptography, stands as one of the oldest and simplest ways to encrypt data. This method uses the same key to encrypt and decrypt information.
Key Characteristics:
The sender and receiver use one key to encrypt and decrypt. Secret-key algorithms work faster and better than public-key ones, making them an excellent choice for encrypting a vast amount of data.
The biggest challenge, however, is to share the key safely between users. If the key is compromised during sharing, the stealer can break into the locked data.
Examples of Symmetric Key Algorithms:
- Advanced Encryption Standard (AES)
- Data Encryption Standard (DES)
- Triple DES (3DES)
Asymmetric Key Cryptography
Asymmetric key cryptography, also called public-key cryptography, solves the problems of symmetric key cryptography by using two different keys: a public key and a private key.
Key Characteristics:
The public key is used to encrypt data, and to decrypt it, the private key is required. The public key is freely available, while the private key remains confidential. As the private key is kept secure, it’s significantly more challenging for attackers to compromise.
Asymmetric methods work slower than symmetric ones, so they don’t work well for encrypting massive amounts of data.
Examples of Asymmetric Key Algorithms:
- RSA (Rivest–Shamir–Adleman)
- Elliptic Curve Cryptography (ECC)
- DSA (Digital Signature Algorithm)
How PKI Combines Symmetric and Asymmetric Cryptography
PKI uses both symmetric and asymmetric cryptography to create a strong security system:
- Asymmetric Cryptography for authentication and key exchange: In most PKI setups asymmetric cryptography helps to set up a safe connection and check who’s involved. For example, when you visit a secure website (HTTPS), your browser uses asymmetric cryptography to share information.
- Symmetric Cryptography for data encryption: After the connection is set up and everyone’s identity is confirmed, symmetric keys often protect the actual data. This happens because symmetric key encryption works faster, making it a good choice for protecting large data transfers.
Application of PKI
PKI is implemented in various sectors to safeguard communications and transactions. Here are some common ways people use it:
- Secure Email Communication: PKI enables individuals to encrypt and digitally sign emails, ensuring that only the authorized recipient can read the message and detect any tampering.
- Secure Web Browsing: SSL/TLS certificates, which are part of PKI, create safe connections between web browsers and servers. This keeps data private and whole when it’s sent.
- Digital Signatures: PKI gives people and companies a way to sign documents. It provides proof that can be checked to show the document is genuine.
- VPNs and Secure Network Access: PKI plays a key role in checking the identity of users and devices that try to access secure networks. It applies to Virtual Private Networks (VPNs) too.
How PKI works:
- First, a user applies for a certificate and generates a key pair: a public key and a private key. Then, the user submits his request with his public key to Registration Authority(RA) for the issuance of a digital certificate.
- Registration Authority(RA) sends a request to the Certification Authority(CA). Here, RA acts as a mediator between the user and CA. RA verifies all the necessary information of the user’s identity.
- Certificate Authority is responsible for issuing and managing digital certificates and generates the public key certificate based on the information provided. The CA signs the certificate with its private key and confirms the validity of the user’s public key.
- CA updates information and sends it to the Validation Authority(VA). VA is responsible for verifying and validating certificates.
- A certificate and digital signature is sent to the user. The user receives the public key certificate and can now use the certificate to sign or encrypt data and send messages with a digital signature.
- Public Key Certificate is used by the receivers. They verify the authenticity of the user by inquiring VA about the validity of the user’s public key certificate.
- The Validation Authority(VA) determines the result. VA compares the public key certificate of the user with that of the updated information provided by the CA and determines the result (valid or invalid).
Conclusion
Public Key Infrastructure stands as a key part of today’s digital security. It allows safe talks, deals, and data sharing across untrusted networks. By mixing the strong points of symmetric and asymmetric key cryptography, PKI offers a flexible and strong system. This system supports many security rules that we need in our digital world today. As technology keeps advancing, PKI will become even more crucial and play a significant role in protecting our information and ensuring we can trust something in the digital world.
