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Digital certificates and TLS Protocol

Digital certificates and the TLS (Transport Layer Security) protocol are foundational technologies for securing communications over the internet. TLS provides the mechanism for establishing an encrypted channel, while digital certificates serve as the identity credentials that allow clients to verify the authenticity of the servers they are connecting to.

Digital Certificates

A Digital Certificate is an electronic document used to prove the ownership of a public key. The certificate includes information about the key as well as the identity of its owner (such as the domain name).^[600-developer-tools-security-000-moc-security.md]

Certificates are typically issued by a Certificate Authority (CA), a trusted third party that validates the identity of the certificate requester.^[600-developer-tools-security-000-moc-security.md] This system is part of a broader framework known as Public Key Infrastructure (PKI).^[600-developer-tools-security-000-moc-security.md]

Certificate Chains and CAs

In public key infrastructure, trust is established through a chain of certificates. The certificate for a specific domain is often not directly signed by a root CA that is trusted by the client's browser or operating system. Instead, it is signed by an intermediate CA.^[600-developer-tools-security-000-moc-security.md]

This creates a certificate chain: 1. The server presents its leaf certificate. 2. It also presents an intermediate certificate from the CA that issued the leaf certificate. 3. The client trusts the intermediate CA because its signature is valid, and it ultimately trusts a Root CA that is pre-installed in the client's trust store.

OpenSSL is a common tool used to generate these certificate chains, specifically creating RSA certificate chains for testing or deployment.^[600-developer-tools-security-000-moc-security.md] Advanced users or organizations may even choose to build their own internal CA structure to manage trust within their private networks.^[600-developer-tools-security-000-moc-security.md]

TLS Protocol

The TLS Protocol (and its predecessor, SSL) is designed to provide secure communication over a computer network. It is widely used to protect web traffic (HTTPS), email, and other forms of data transmission.^[600-developer-tools-security-000-moc-security.md]

The TLS Handshake

When a client connects to a server using TLS, they perform a "handshake" to establish a secure connection. This process involves several steps:

  1. Client Hello: The client sends a message listing supported cipher suites and a random number.
  2. Server Hello: The server selects a Cipher suite and sends its digital certificate.^[600-developer-tools-security-000-moc-security.md]
  3. Verification: The client verifies the server's certificate using the CA's public key (checking the signature and validity period).
  4. Key Exchange: The client uses the information in the certificate (the server's public key) to encrypt a "pre-master secret" or perform a Diffie-Hellman exchange. This allows both the client and server to generate a shared session key.
  5. Secure Communication: The session key is then used to symmetrically encrypt all subsequent application data sent between the parties.^[600-developer-tools-security-000-moc-security.md]

This combination of asymmetric encryption (for the handshake and key exchange) and symmetric encryption (for the data transfer) provides both security and performance.

  • OpenSSL
  • [[Public Key Infrastructure (PKI)]]
  • [[Certificate Authority (CA)]]
  • [[HTTPS]]

Sources

  • 600-developer-tools-security-000-moc-security.md