What are the pros and cons of 1024-bit vs 2048-bit DKIM keys?

Summary

The consensus is that 2048-bit DKIM keys offer stronger security compared to 1024-bit keys, making them harder to crack and forge. While 1024-bit keys are still supported and may be acceptable for some use cases, 2048-bit keys are increasingly recommended as the industry standard for enhanced security and future-proofing. However, potential drawbacks include compatibility issues with older MTAs and DNS systems, as well as difficulties in managing longer DNS TXT records. Experts recommend considering organizational needs, security requirements, and potential infrastructure limitations before making a decision.

Key findings

  • Enhanced Security: 2048-bit keys provide significantly stronger encryption, making them harder to crack and reducing the risk of email spoofing.
  • Industry Standard: 2048-bit keys are becoming the industry standard and are recommended for long-term security.
  • Functionality of 1024-bit Keys: 1024-bit keys may still function adequately, but they offer less protection against modern threats.

Key considerations

  • Compatibility: Older MTAs and DNS systems may experience compatibility issues with 2048-bit keys.
  • DNS Management: Managing longer 2048-bit DKIM records can be challenging due to DNS TXT record size limitations, potentially requiring record splitting or alternative DNS management methods.
  • Organizational Requirements: Organizations handling sensitive data or subject to strict regulatory requirements may need to prioritize the enhanced security of 2048-bit keys.
  • Effort vs. Benefit: Consider the effort required to implement 2048-bit keys against the incremental security benefit, especially if existing systems are already secure and regularly monitored.

What email marketers say
14Marketer opinions

The primary advantage of a 2048-bit DKIM key over a 1024-bit key is enhanced security due to the increased difficulty in cracking or forging signatures. While 1024-bit keys may still be functional and compliant with some standards, they are increasingly considered less secure and may not offer sufficient protection against sophisticated attacks. However, potential drawbacks of 2048-bit keys include compatibility issues with older mail transfer agents (MTAs) or DNS systems, as well as challenges in managing longer DNS TXT records.

Key opinions

  • Security: 2048-bit keys offer significantly stronger encryption and are more resistant to cracking or forging compared to 1024-bit keys.
  • Industry Standard: 2048-bit keys are increasingly becoming the industry standard and are recommended for future-proofing security measures.
  • Vulnerability: 1024-bit keys are more vulnerable and easier to crack.
  • Mitigation: Using 2048 keys can better protect from email spoofing.

Key considerations

  • Compatibility: Older MTAs and DNS systems might have compatibility issues with 2048-bit keys.
  • DNS Management: Longer 2048-bit keys can pose challenges in DNS management due to TXT record size limitations, potentially requiring record splitting.
  • Compliance: While 1024-bit keys may still be acceptable, some regulations or security requirements may necessitate the use of 2048-bit keys.
  • Organizational Need: Military, government, or financial institutions may require more secure 2048-bit keys.
Marketer view

Marketer from Email Geeks shares that 1024-bit keys are still okay unless you work in military-related fields.

October 2024 - Email Geeks
Marketer view

Email marketer from StackExchange explains that 2048-bit keys are longer, which makes them more secure and harder to crack. However, some older systems or DNS providers might have issues with the increased length of the key, especially when manually configuring DNS records.

August 2022 - StackExchange
Marketer view

Email marketer from StackOverflow explains that DNS TXT record size limitation can cause issues with 2048 bit key deployment in some situations, and splitting the record is required.

March 2022 - StackOverflow
Marketer view

Email marketer from EasyDMARC shares that using a 2048-bit DKIM key is recommended for enhanced security. They explain that while 1024-bit keys are still functional, they are more vulnerable to being cracked compared to the stronger 2048-bit keys, which offer a higher level of encryption and protection.

September 2022 - EasyDMARC
Marketer view

Email marketer from StackExchange notes that while 2048 is better, some older systems might struggle. He also mentions potential issues with pasting long records into DNS management tools.

August 2024 - StackExchange
Marketer view

Email marketer from Reddit explains that transitioning to 2048-bit DKIM keys is a good security practice. They recommend rotating DKIM keys periodically and using 2048-bit keys for better protection against email spoofing.

March 2024 - Reddit
Marketer view

Email marketer from Reddit shares that a 2048-bit key is better because a 1024-bit key is easier to crack. The longer the key, the more computationally expensive it is to forge a signature.

November 2024 - Reddit
Marketer view

Marketer from Email Geeks reports no deliverability loss since switching to a 2048-bit key and are pushing forward with global implementation for all clients.

March 2023 - Email Geeks
Marketer view

Email marketer from StackExchange explains that the cost of using 2048 bits is almost negligible, and the advantage of the higher encryption is significant. Given current computing capabilities, 1024 bit may be considered unacceptably weak in some circles now.

October 2024 - StackExchange
Marketer view

Email marketer from Mailhardener states that 2048 bit keys are more secure than 1024-bit keys. They state that 2048 bit keys are recommended to avoid potential issues and increase the longevity of the keys. They also state that while 1024 bit keys are accepted the industry standard is now 2048-bit keys.

July 2023 - Mailhardener
Marketer view

Marketer from Email Geeks notes that the RFC for DKIM still says 1024-bit is acceptable for marketing email. 2048-bit is better for government or financial institutions. Older MTAs may have issues with 2048-bit keys.

August 2023 - Email Geeks
Marketer view

Marketer from Email Geeks explains that the difference between 1024-bit and 2048-bit keys is the length of the key, and longer keys are harder to crack.

June 2023 - Email Geeks
Marketer view

Email marketer from MXToolbox says that while some providers may allow 1024 bit key, 2048 bit is more secure and the recommended key length to use.

August 2024 - MXToolbox
Marketer view

Email marketer from RPGPGM.COM explains that the longer the DKIM key is, the harder it is to forge signatures. A 2048-bit key is significantly more secure than 1024-bit but older versions of IBM iSeries might not support it.

December 2023 - RPGPGM.COM

What the experts say
7Expert opinions

Experts suggest that while 1024-bit keys might still be functional and acceptable, 2048-bit keys offer better security and future-proofing against increasingly sophisticated attacks. Operationally, the difference may not be significant for most users. However, managing 2048-bit keys can be challenging with some DNS management interfaces, and older systems might not support them. A key motivator for upgrading to 2048-bit is often to meet security best practices and avoid criticism, not necessarily because 1024-bit is immediately vulnerable.

Key opinions

  • Enhanced Security: 2048-bit keys offer better security due to the increased difficulty in forging signatures and future-proofing.
  • Operational Similarity: Operationally, there isn't a huge difference between 1024 and 2048 bit keys for most use cases.
  • Limited Compatibility Concerns: Most mailservers should be able to handle 2048 bit keys.

Key considerations

  • DNS Management Issues: Managing 2048-bit keys in DNS can be problematic, especially with low-end web interfaces, potentially requiring record splitting.
  • Legacy System Support: Consider compatibility with older MTAs when implementing 2048-bit keys.
  • Security Consultant Scrutiny: Upgrading to 2048-bit keys can preempt criticism and satisfy security best practices, even if 1024-bit is currently sufficient.
Expert view

Expert from Email Geeks shares that using a 2048-bit key can be painful if you manage DNS yourself via your domain registrar portal, as it may not fit and require splitting.

August 2022 - Email Geeks
Expert view

Expert from Email Geeks explains that while a 1024-bit key is currently fine against reasonably funded attackers, the main reason to use 2048-bit keys is to avoid criticism from security consultants.

November 2021 - Email Geeks
Expert view

Expert from Email Geeks says that operationally, there isn't much difference between 1024 and 2048 bit DKIM keys and that 2048 is fine.

December 2024 - Email Geeks
Expert view

Expert from Email Geeks shares they would be surprised if any noticeable number of mailservers failed to handle a 2048 bit key as they see them used a lot, including mainstream ecommerce sites.

March 2024 - Email Geeks
Expert view

Expert from Spam Resource shares that longer keys are more difficult to forge signatures. Therefore, using 2048 bit is safer than 1024. However, Spam Resource doesn't seem to explicitly weigh the pros and cons of each key.

January 2022 - Spam Resource
Expert view

Expert from Word to the Wise suggests using 2048-bit keys because they are more secure, even though 1024-bit keys may still be accepted by some providers. It's about future-proofing and making sure that your keys aren't easily cracked. However, you must consider if you have legacy MTAs still in use.

January 2025 - Word to the Wise
Expert view

Expert from Email Geeks explains that 2048-bit keys implementation is riddled with bugs and crappy implementation in low-end DNS management web interfaces.

December 2024 - Email Geeks

What the documentation says
4Technical articles

Documentation consistently points to 2048-bit DKIM keys offering enhanced security compared to 1024-bit keys. While 1024-bit keys are supported, 2048-bit or greater keys are recommended for better protection against attacks.

Key findings

  • Stronger Security: 2048-bit DKIM keys are more secure and harder to crack than 1024-bit keys.
  • Recommendation: Industry documentation recommends using 2048-bit DKIM keys for better security.
  • Vulnerability: 1024-bit keys provide a lower level of protection against attacks.

Key considerations

  • Support: 1024-bit keys must be supported; however, 2048 is still the recommendation.
Technical article

Documentation from Google explains that a 2048-bit key provides more security than a 1024-bit key. In the Admin console you can generate a DKIM key with a bit length of 1024 bits or 2048 bits. A 2048-bit key is more secure than a 1024-bit key.

October 2022 - Google
Technical article

Documentation from Cloudflare explains that a 2048 bit key is stronger and recommended over 1024 bit.

September 2024 - Cloudflare
Technical article

Documentation from ietf.org (RFC 6376) specifies that while key sizes of 1024 bits MUST be supported, key sizes of 2048 bits or greater are RECOMMENDED.

October 2023 - ietf.org
Technical article

Documentation from DigiCert explains that using a 2048-bit DKIM key is more secure than a 1024-bit key because it is significantly more difficult to crack. Although 1024-bit keys may still be functional, they do not offer the same level of protection against sophisticated attacks. They recommend 2048-bit DKIM keys.

November 2024 - DigiCert