What tools and methods are available to generate DKIM public and private keys?

Key findings

• Online generators: Many web-based tools simplify the process, requiring only basic domain information to produce both keys and the corresponding DNS record. These are often preferred for their ease of use and speed.
• Command-line tools: Utilities like OpenSSL and OpenDKIM offer greater control over key parameters (such as length and format) and are commonly used by system administrators and experts.
• Key format importance: The private key must often be in a specific format, such as PKCS#1 RSA private key in PEM format, for successful upload to email service providers (ESPs) or mail servers.
• Underlying technology: Many online DKIM generators internally use OpenSSL, providing a reliable and standardized method for key generation.

Key considerations

• Security of private key: The private key must be kept absolutely secure and confidential. Its compromise can lead to email spoofing issues.
• Compatibility: Ensure the generated keys are compatible with your specific email platform or ESP, paying close attention to required formats and lengths.
• Validation: Always validate your DKIM setup after generating and publishing keys. Tools like DKIM checkers can confirm correct implementation. You can learn more about this in our guide on how to verify DMARC, DKIM, and SPF setup.
• DNS record publishing: The public key needs to be correctly published as a DNS TXT record. This involves adding the key to your domain's DNS settings. For details, refer to how SPF, DKIM, and DMARC records should be placed. A helpful external reference for generating the full record can be found at Sendmarc's DKIM Record Generator.

Key opinions

• Preference for simplicity: Marketers often prefer tools that generate keys quickly with minimal configuration, especially for testing or initial setup.
• Format issues: A common challenge is ensuring the private key is in the precise format required by the email sending platform, such as PKCS#1 RSA in PEM format, to avoid upload errors.
• System specific requirements: Some systems mandate that users generate their own DKIM keys, but may offer limited support or guidance on the correct procedure or required format.
• Visual clarity: Marketers may prefer keys that appear 'cleaner' or more familiar in structure, as unusual spacing or characters can raise concerns about validity, even if technically correct.

Key considerations

• Tool reliability: It's important to use reputable online DKIM generators to ensure the keys are cryptographically sound and correctly formatted.
• Troubleshooting: Be prepared to troubleshoot if a generated key isn't accepted, often checking error messages for specific format requirements. Our article on troubleshooting DKIM issues can be helpful.
• Post-generation validation: Always validate the DKIM record after publication to ensure it's correctly recognized by mail servers, preventing issues like “no DKIM record found” errors.
• Seeking external resources: When facing difficulties, external guides can provide step-by-step instructions. For example, the IONOS Digital Guide offers advice on creating a DKIM record.

Key opinions

• OpenSSL as standard: OpenSSL is widely recognized and used for generating DKIM keys, providing robust cryptographic capabilities and flexibility.
• OpenDKIM utility: OpenDKIM is another frequently cited tool for key generation, often favored by those managing mail servers.
• Online tool transparency: Experts appreciate online generators that are transparent about using well-known libraries like OpenSSL, as this instills confidence in the key's integrity.
• Testing vs. production: Simple online tools like Dkimcore.org are often recommended for testing and educational purposes due to their straightforward nature.

Key considerations

• Private key management: Emphasize secure storage of the private key, as its compromise directly impacts email authentication. For more on DKIM, including key selectors, see our guide on DKIM selector name examples.
• Key length and algorithm: Experts advise using strong key lengths (e.g., 2048 bits for RSA) to ensure cryptographic strength and avoid common errors like DKIM temperrors.
• Validation best practices: Always validate generated keys and the corresponding DNS record. Resources from sites like Spamresource often provide insights into common pitfalls.
• Understanding key types: Differentiating between PKCS#1 and PKCS#8 PEM formats can be crucial for compatibility with certain systems.

Key findings

• Standard tools: Documentation frequently points to established command-line tools like OpenSSL and ssh-keygen for generating RSA key pairs.
• Key format specifics: There is a strong emphasis on the private key being in the correct PEM format, often specifically PKCS#1, for compatibility with various email systems.
• Public key in DNS: The public key is consistently directed to be published as a DNS TXT record, alongside a specified selector.
• Importance of selectors: Documentation highlights that key selectors are critical for managing multiple DKIM keys for a single domain and for facilitating key rotation.

Key considerations

• Adherence to standards: Always follow the key length and algorithm recommendations (e.g., 2048-bit RSA) outlined in official DKIM RFCs and best practices. These standards also underpin how DMARC works with SPF and DKIM.
• Secure private key handling: Documentation consistently stresses the need to securely store the private key, as it's the cryptographic signature for your emails.
• System-specific guidance: While general tools exist, refer to your email service provider's or mail server's specific documentation for precise instructions on generating and implementing DKIM. This is especially important for services like setting up DKIM for emails from a web server.
• DNS publication details: Pay attention to the exact format required for the DNS TXT record, including quotes and spacing, to ensure proper interpretation by DNS resolvers. Rackspace offers an example in their documentation on creating a DKIM TXT record.