What Is Key Rotation in DKIM?

What is Key Rotation in DKIM?

Key rotation refers to the regular replacement of cryptographic keys used in digital signing and encryption. In email authentication, it typically applies to DKIM keys, which verify message integrity and sender identity. Rotating keys helps prevent compromise, limits exposure from old or leaked keys, and maintains compliance with security best practices.

Each DKIM signature relies on a private key to sign messages and a public key published in DNS. Over time, keys can become vulnerable if not refreshed, particularly in large organizations using multiple senders or automated systems. Regular rotation ensures the cryptographic chain of trust remains secure.

How Key Rotation Works

When rotating DKIM keys, administrators follow a process to introduce new selectors without interrupting email authentication:

• Generate a new DKIM key pair (private and public)
• Publish the new public key in DNS under a new selector (e.g., selector2._domainkey.example.com)
• Update the mail server or sending service to use the new private key for signing
• Monitor message signatures to confirm the new key functions correctly
• Remove the old key from DNS after a safe transition period

This phased approach ensures continuity while minimizing the risk of invalid signatures or message rejections.

Best Practices for DKIM Key Rotation

• Rotate keys every 6–12 months depending on security needs
• Use at least 1024-bit keys (2048-bit is recommended)
• Assign different selectors to different services or sending platforms
• Remove inactive or unused selectors promptly
• Monitor authentication results through DMARC reports

Key Rotation and DMARCeye

DMARCeye continuously monitors the DKIM selectors and public keys published across your domains using AI-powered technology and smart programming. The platform detects expired, inactive, or duplicate keys and provides insights into their usage frequency and validity.

By tracking key rotation and authentication outcomes, DMARCeye helps organizations maintain cryptographic hygiene and ensure all DKIM signatures remain valid and trustworthy.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.