DKIM (DomainKeys Identified Mail)
DKIM (DomainKeys Identified Mail) Definition
DKIM, or DomainKeys Identified Mail, is an email authentication method that allows an organization to take responsibility for a message that is in transit. DKIM adds a digital signature to the email header, verifying that the message has not been altered during transit and that it comes from the specified domain.
How DKIM Works
To implement DKIM, the sender's outgoing mail server creates a unique cryptographic signature for each email sent. This signature is generated using a private key that is kept secure within the organization. The signature is then added to the email header.
When a recipient's email server receives the email, it can use the public key published in the sender's DNS records to authenticate the email. The recipient's email server can verify the DKIM signature, ensuring that the content of the email has not been altered in transit. If the signature does not match, it alerts the recipient that the message may be fraudulent.
The DKIM signature includes information such as the domain of the sender, the selector (a string used to select the public key from the DNS), the algorithm used to create the signature, and the signature itself. This information allows the recipient's email server to verify the integrity and authenticity of the email.
Prevention Tips
To effectively use DKIM:
Organizations should configure their outgoing mail servers to sign outbound emails with DKIM. This ensures that all outgoing messages are digitally signed, allowing the receiving email servers to verify the authenticity of the messages.
Recipients' mail servers must be configured to verify DKIM signatures. By checking the DKIM signature on incoming emails, email servers can ensure that the messages have not been tampered with during transit.
It is important to regularly monitor and update the keys used for DKIM to maintain security. Over time, cryptographic algorithms may become vulnerable or private keys can be compromised. Organizations should follow best practices for key management, including rotating keys periodically and following strong security protocols.
By implementing DKIM, organizations can authenticate their email messages and reduce the risk of email-based fraud, such as phishing or email spoofing. DKIM provides an additional layer of trust and verification for both senders and recipients, enhancing the overall security of email communications.
Related Terms
SPF (Sender Policy Framework): SPF is another email authentication method that detects forging sender addresses. It verifies whether an email message originates from an authorized server for a given domain by comparing the sending server's IP address to the records in that domain's DNS.
DMARC (Domain-based Message Authentication, Reporting, and Conformance): DMARC is an email authentication and reporting protocol that builds on SPF and DKIM. It allows senders to specify policies for email handling and provides visibility into email authentication failures. DMARC helps prevent email fraud by instructing mail servers on how to handle emails that fail SPF and DKIM checks, reducing the chances of successful phishing attacks.