Summary
Generating an a=rsa-sha256 key for DKIM involves using cryptographic tools like OpenSSL to create a public and private key pair. This process is crucial for email authentication, helping to verify that an email was sent by the domain it claims to be from and that its content has not been altered in transit. Various tools are available, but for maximum security and control, direct generation using command-line utilities is often preferred over online services, which may pose security risks by potentially storing private keys. Key length, such as 2048-bit RSA, is a significant factor in the strength of the DKIM signature.
Key findings
- OpenSSL is the primary tool: Most experts recommend using OpenSSL for generating DKIM key pairs, offering a secure and flexible method via the command line.
- Security concerns with online generators: While convenient, online DKIM key generators carry the risk of the private key being stored or exposed on a third-party server.
- Key length matters: A longer key length, such as 2048 bits, provides enhanced security for your DKIM signatures, making them more resilient against cryptographic attacks.
- RSA-SHA256 is standard: The RS256 algorithm is widely accepted and recommended for DKIM implementation.
Key considerations
- Private key management: Securely storing your private key is paramount to prevent unauthorized email signing.
- DNS record publishing: After generation, the public key must be published as a TXT record in your domain's DNS to enable verification.
- Regular key rotation: Periodically rotating your DKIM keys is a best practice for maintaining security.
- Compatibility: Ensure your email service provider supports the chosen key length and algorithm (a=rsa-sha256).
What email marketers say
Email marketers often seek the easiest and most accessible methods for DKIM key generation, sometimes opting for online tools due to their simplicity. However, the community also highlights the importance of security and the nuances of key length and management for optimal email deliverability.
Key opinions
- Online generators for ease: Many marketers find online DKIM key generators convenient, allowing for quick setup without deep technical knowledge.
- Prioritizing security: Despite convenience, some marketers express concern about the security implications of trusting third-party websites with their private keys.
- Longer keys for better security: There's a general consensus among marketers that maximizing key length, such as using 2048-bit keys, enhances security.
- Seeking practical guidance: Marketers frequently look for straightforward guides and scripts to generate keys themselves, reducing reliance on external tools.
Key considerations
- Balancing ease and security: Marketers must weigh the simplicity of online generators against the potential security risks.
- Impact on deliverability: Proper DKIM setup is understood to be critical for inbox placement and overall email authentication.
- Understanding key length acceptance: Marketers frequently inquire about which key lengths are widely accepted by ISPs to ensure broad compatibility.
- Troubleshooting common issues: The process can be confusing, leading to questions about troubleshooting and validating the generated key.
Marketer view
Marketer from Email Geeks suggests checking out online DKIM generators for a straightforward way to get started with key creation. These tools often simplify the process significantly for users who prefer not to use command-line interfaces. They are a good entry point for quick setup.
Marketer view
Marketer from Stack Overflow wonders if generating a key pair (e.g., .key and .cert files) for DKIM using OpenSSL is an acceptable method. They inquired about standard practices, specifically noting the use of openssl req -newkey rsa:2048 -sha256 -x509 -nodes -days 3650 for key generation.
What the experts say
Deliverability experts emphasize the critical importance of self-generating DKIM keys for security, steering clear of potential vulnerabilities associated with online tools. They highlight OpenSSL as the industry standard and stress the significance of appropriate key lengths and secure management practices.
Key opinions
- Self-generation is key: Experts strongly advise against using public online key generators due to the inherent trust required for private key security. Generating keys on your own system is recommended.
- OpenSSL is the go-to: OpenSSL is widely recognized as the most reliable and secure method for generating RSA-SHA256 keys from a Linux/Unix command line.
- Ease of command-line tools: Despite initial perceptions, creating keys via the command line is considered relatively easy once the commands are known.
- ESPs often direct to DKIM.org: Many Email Service Providers (ESPs) refer users to DKIM.org for generating keys and understanding specifications.
Key considerations
- Risk of private key exposure: The primary concern with online tools is the potential for the private key to be compromised if the site's security is breached.
- Scripting for automation: For ongoing needs or multiple domains, scripting the OpenSSL key generation process can be highly efficient.
- Proper key length selection: While 2048-bit keys are generally preferred for security, it is important to check ISP acceptance of larger keys.
- Understanding DKIM failures: Incorrect key generation or publishing can lead to DKIM failures, impacting deliverability and requiring diligent troubleshooting.
Expert view
Expert from Email Geeks strongly advises caution when using online services to generate DKIM public and private keys, emphasizing the inherent trust involved. There's a risk that the website might not securely manage or might inadvertently expose the private key to unauthorized parties.
Expert view
Expert from SpamResource explains that selecting a robust key length, such as 2048 bits for RSA keys, is crucial for future-proofing your DKIM implementation. They suggest that longer keys provide a stronger cryptographic barrier against brute-force attacks and evolving computing capabilities.
What the documentation says
Official documentation and technical guides provide precise instructions and best practices for generating DKIM keys, primarily emphasizing the use of robust cryptographic methods like OpenSSL and adherence to industry standards for key types and lengths. They underscore the importance of proper implementation for secure email communication.
Key findings
- OpenSSL commands are foundational: Detailed OpenSSL commands are provided for creating RSA private and public keys for DKIM, specifying algorithms like SHA256.
- RFC compliance: Documentation often refers to RFCs (Request for Comments) that define the technical specifications for DKIM, including key generation.
- Key size recommendations: While 1024-bit keys are functional, 2048-bit keys are increasingly recommended for stronger security.
- Public key format for DNS: Instructions specify how to format the public key into the correct TXT record format for DNS publication.
Key considerations
- Algorithm specification: The 'a=' tag in the DKIM record specifies the algorithm used (e.g., rsa-sha256), which must match the generated key.
- Private key security: Documentation consistently stresses the importance of keeping the private key confidential and secure.
- Compatibility with receiving servers: Using recommended key lengths ensures broad compatibility with various mail transfer agents (MTAs) and email providers.
- Integration with DMARC and SPF: DKIM functions as part of a broader email authentication framework, alongside SPF and DMARC, as outlined in technical guides and specifications like DKIM specifications.
Technical article
Documentation from Mailhardener.com provides a guide on how to create DKIM records using the popular open-source OpenSSL suite. It specifies that this method is suitable for email server administrators or developers who need to send email from their software, emphasizing control.
Technical article
Documentation from DKIM.org (via Mailhardener.com) outlines the process for generating a new set of DKIM public and private keys. It emphasizes the need to enter your domain and email delivery key selector, guiding users through the essential steps for setup.
Related resources
7 resources
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