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Summary

DKIM key rotation is widely recommended to minimize the impact of compromised keys by reducing the exposure window and preventing unauthorized use, while also ensuring the key management process is functional and up-to-date. It is considered a proactive email security strategy, ensuring regular security updates and maintenance, as well as standardizing processes. A 2048-bit key length is considered the industry standard for enhanced security, offering better protection against cryptographic attacks and ensuring compliance with email authentication standards. Although strict guidelines for rotation frequency may not exist, rotating keys at least annually or every 6-12 months is considered a good practice. The DKIM standard supports publishing multiple public keys to facilitate seamless key rotation without service interruption. While RSA-512 is considered easily cracked, 2048-bit is currently acceptable although future vulnerabilities are possible.

Key findings

Reduced Exposure: DKIM key rotation reduces the window of exposure if a private key is compromised.
Proactive Security: It's a proactive email security strategy, ensuring regular updates and preventing long-term exploitation.
Industry Standard Key: 2048-bit key length is the industry standard for enhanced security and compliance.
Process Standardization: Frequent rotations standardize the process and ensure institutional knowledge.
Seamless Rotation: Publishing multiple public keys allows for key rotation without service interruption.

Key considerations

Rotation Frequency: Rotate keys at least annually or every 6-12 months for optimal security.
Key Removal: Remove old keys after a window to ensure validation.
RSA-512 Vulnerability: RSA-512 keys are easily cracked; 1024-bit keys are also vulnerable.
Attack Vectors: Attack vectors are more likely insider threats or data leakage than brute force.
Incident Response: Regular key rotation ensures the incident response plan is well understood.

What email marketers say

12 marketer opinions

DKIM key rotation is recommended to minimize the impact of compromised keys, ensure the key management process functions correctly, and proactively address potential security vulnerabilities. Regular rotation limits the time a compromised key can be exploited and validates key management processes. A 2048-bit key length is considered secure and is now the industry standard, providing enhanced security against cryptographic attacks. Consistent maintenance and periodic checks of email infrastructure are also enforced through key rotation.

Key opinions

Compromised Key Mitigation: Rotating keys limits the damage from a compromised key by reducing the time it can be exploited.
Proactive Security: Key rotation is part of a proactive email security strategy, ensuring measures are regularly updated.
Industry Standard Key Length: A 2048-bit DKIM key length is now considered the industry standard for enhanced security and deliverability.
Standardized Processes: Frequent rotations standardize the rotation process and ensure institutional knowledge is available for emergencies.

Key considerations

Key Removal: Remove old keys after a window of time to ensure validation, involving adding a new key, signing with the new key, and then removing the old key's TXT record.
Rotation Frequency: Rotate keys at least once a year or every 6-12 months for optimal security.
RSA-512 Vulnerability: RSA-512 keys are easily cracked, and while 1024-bit keys haven't been factored yet, it's only a matter of time.
Ongoing Protection: DKIM rotation provides ongoing protection against sophisticated email attacks and maintains the integrity of email communications.

Marketer view

Email marketer from Reddit explains that DKIM key rotation is crucial for mitigating risks associated with key compromise, insider threats, and vulnerabilities in cryptographic algorithms. They also mention that it enforces periodic checks on your email infrastructure.

25 Apr 2023 - Reddit

Marketer view

Email marketer from Valimail explains that rotating DKIM keys limits the damage from a compromised key by reducing the time it can be exploited. It also validates that the key management process is working as intended.

13 Sep 2022 - Valimail

What the experts say

4 expert opinions

DKIM key rotation is recommended to limit the exposure window if a private key is compromised, and to ensure the rotation process is understood and functional. While RSA is considered legacy, a 2048-bit key length is acceptable and increasingly important for DKIM signatures due to security enhancements and compliance. Rotating keys every 6 to 12 months is considered a good practice to mitigate potential damage and enforce regular maintenance.

Key opinions

Exposure Window Reduction: DKIM key rotation reduces the window of exposure if a private key is compromised.
2048-bit Key Length: Using a DKIM key length of 2048 bits is increasingly important for improved security and compliance.
Regular Rotation: Rotating DKIM keys every 6 to 12 months is a good practice for mitigating potential damage and enforcing maintenance.

Key considerations

Attack Vectors: Attack vectors are more likely to be insider, data leakage, or 'rubber hose' rather than brute force, even for a 1024-bit key.
Lack of Strict Guidelines: Strict guidelines for rotation frequency don't exist, but 6-12 months is a recommended interval.
Ensuring Rotation Process: Rotating keys regularly ensures that you know how to rotate them cleanly when you discover (or suspect) your private key is compromised

Expert view

Expert from Email Geeks explains that while RSA is considered legacy, 2048 is acceptable for DKIM signatures because the attack vectors are more likely to be insider, data leakage, or rubber hose rather than brute force, even for a 1024-bit key.

31 Dec 2021 - Email Geeks

Expert view

Expert from Spam Resource explains that while strict guidelines don't exist, rotating DKIM keys every 6 to 12 months is a good practice. This mitigates potential damage from compromised keys and enforces regular maintenance.

9 Dec 2023 - Spam Resource

What the documentation says

4 technical articles

DKIM key rotation is recommended to reduce the risk of unauthorized key use and minimize damage from spoofing or phishing. It is considered a defense-in-depth security strategy, beneficial even if a key isn't compromised. A 2048-bit key length offers better security against cryptographic attacks, though 1024-bit keys may still be supported. The DKIM standard (RFC 6376) supports publishing multiple public keys, facilitating seamless key rotation without service interruption.

Key findings

Reduced Unauthorized Use: DKIM key rotation reduces the risk of unauthorized use if a key is compromised.
2048-bit Security: 2048-bit keys offer better security against cryptographic attacks compared to 1024-bit keys.
Defense-in-Depth: Regularly rotating DKIM keys provides a defense-in-depth strategy, even if a key isn't compromised.
Seamless Rotation: The DKIM standard allows publishing multiple public keys for key rotation without service interruption.

Key considerations

Transition Period: During key rotation, older keys can remain valid for a transition period while senders switch to new keys.
Key Support: While 2048-bit keys are recommended, 1024-bit keys may still be supported by some systems.
Minimizing Damage: Regular key rotation limits the period a compromised key can be used, thereby minimizing potential damage.

Technical article

Documentation from AWS SES Documentation answers that regularly rotating DKIM keys provides a defense-in-depth strategy. Even if a key isn't compromised, rotating it is a security best practice.

15 May 2022 - AWS SES Documentation

Technical article

Documentation from Google Workspace Admin Help explains that DKIM key rotation reduces the risk of unauthorized use if a key is compromised. Regularly rotating keys limits the period a compromised key can be used, thereby minimizing potential damage from spoofing or phishing attacks.

15 Oct 2023 - Google Workspace Admin Help