DomainKeys Identified Mail (DKIM) is a cryptography-based authentication mechanism for email sending. It allows for the verification of the integrity of messages as well as the legitimacy of the sender, thereby offering better protection against identity theft and phishing attacks. In this article, we’ll delve into how DKIM operates and explain how it contributes to the security of email communications.
What is DKIM?
DKIM is an authentication protocol that uses asymmetric cryptography to verify the integrity of key fields in an email. The concept is straightforward: when sending a message, the sender generates a DKIM signature by creating a hash of certain fields of the message (like the “From” or “Subject” fields) and encrypts it using their private key. The recipient, in turn, should be able to retrieve this public key to decrypt the DKIM signature and validate the message’s integrity.
- DKIM ensures that emails genuinely come from the stated sender and haven’t been altered during transit.
- Through cryptographic authentication, DKIM prevents identity spoofing and phishing attempts.
Process of Generating and Verifying the DKIM Signature
Step 1: Creating the hash of the message fields
When sending an email, the sender’s sending platform creates a hash of the fields included in the DKIM signature. For instance, for the fields:
From: Jane Doe <jane.doe@email.com> Subject: Update
The corresponding hash would be:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBC......
Step 2: Encryption with the sender’s private key
Once the hash is generated, it’s encrypted with a private key that only the sender possesses. To do this, they must find the public key that perfectly matches their private key, allowing the DKIM signature to be decrypted and retrieve the initial hash. This public key is located in a specific DNS record for that sender.
Step 3: Hash comparison by the recipient
Finally, the recipient generates their hash of the fields included in the DKIM signature found in the received message and compares this hash with the one decrypted using the previously obtained public key. If both hashes match, it indicates that the DKIM fields haven’t been altered during transit, and the sender is genuinely who they claim to be.
Benefits of DKIM for Email Security
Using DKIM offers several advantages for enhancing security in email exchanges:
- Sender Authentication: the recipient can verify if the sender is indeed the one claiming to send the email, helping to combat identity impersonation.
- Message Integrity: by comparing hashes, it ensures that the message content hasn’t been altered during transit.
- Increased trust in email sending: with DKIM, reputable service providers are better protected against abuses, and their deliverability is enhanced.
- Reduction of spam and phishing: by making identity theft and malicious message sending more challenging, DKIM helps curb the spread of these cybercrime methods.
DomainKeys Identified Mail is a crucial process for bolstering email communication security, just like SPF or DMARC. By using cryptographic authentication to guarantee the integrity and origin of messages, it effectively combats identity spoofing and phishing attacks. However, DKIM is just one element of the security chain. It’s also essential to adopt sound practices regarding password management and the use of secure protocols for data exchange.
