Software-Engineering

Let’s Encrypt: Free Certificate Authority

What is Let’s Encrypt?

Let’s Encrypt is a free, automated, and open Certificate Authority (CA) that provides digital certificates needed to enable HTTPS (SSL/TLS) encryption on websites. It was launched in 2016 by the Internet Security Research Group (ISRG) and is sponsored by major companies including Mozilla, Cisco, and EFF.

Why is Let’s Encrypt Needed?

Let’s Encrypt addresses critical issues in web security:

• Cost Barrier: Traditional certificates cost money, preventing small sites from using HTTPS
• Complexity: Manual certificate management is error-prone and time-consuming
• Security Gap: Many websites remain unencrypted due to certificate costs
• Automation: Enables automated certificate lifecycle management
• Trust: Provides certificates trusted by all major browsers

How Does Let’s Encrypt Work?

Let’s Encrypt uses the ACME (Automatic Certificate Management Environment) protocol to:

1. Verify Domain Ownership: Through HTTP-01 or DNS-01 challenges
2. Issue Certificates: Free DV (Domain Validation) certificates
3. Automate Renewal: Certificates valid for 90 days to encourage automation
4. Maintain Trust: Cross-signed by IdenTrust for broad compatibility

graph TD
    A[Website Owner] --> B[ACME Client<br/>e.g., Certbot]
    B --> C[Let's Encrypt CA]
    C --> D[Domain Validation]
    D --> E[Certificate Issuance]
    E --> F[Installation]
    F --> G[Auto-Renewal]