How to Get a Let's Encrypt Certificate with an ECDSA Key

Let's Encrypt supports ECDSA key types for improved performance and smaller certificate sizes. This guide walks through the specific troubleshooting steps to diagnose and resolve ECDSA key type configuration.

Before You Begin

Before you begin, be sure to have the following in place:

• A Linux server with the relevant software installed
• Access to the command line interface
• Appropriate permissions (root or sudo)

Quick Fix

Wrong

certbot certonly --nginx -d example.com --key-type rsa

Wrong: Defaulting to RSA key type

Right

certbot certonly --nginx -d example.com --key-type ecdsa --elliptic-curve secp384r1

Right: Requesting ECDSA with P-384 curve

Output

Saving debug log to /var/log/letsencrypt/letsencrypt.log\nPlugins selected: Authenticator nginx\nObtaining a new certificate\nRequested key type: ecdsa\nRequested elliptic curve: secp384r1\nKey type: ECDSA (secp384r1)\nSuccessfully received certificate.

Prevention

To avoid future issues, follow these best practices:

• Use --key-type ecdsa for smaller, faster certificates
• Specify the curve with --elliptic-curve secp384r1 for stronger security
• EC keys improve TLS handshake performance, especially on mobile devices
• Let's Encrypt supports both P-256 (prime256v1) and P-384 (secp384r1)
• Verify the key type with openssl x509

DodaTech Tools

For further assistance with any of the above issues, consider using DodaTech consulting services or DodaTech tutorials for more in-depth guidance.

Common Mistakes with ecdsa key

1. Non-exhaustive pattern matches that compile with warnings then crash at runtime
2. Misunderstanding that String is [Char] with poor performance for large text operations
3. Using foldl instead of foldl' causing stack overflow on large lists

These mistakes appear frequently in real-world LETSENCRYPT code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ