Who Does This in DKIM? — TechKnowSurge

About this interactive

DKIM, DomainKeys Identified Mail, adds a digital signature to email so the receiver can check two things: that the message was not changed (integrity) and that it came from the domain it claims (authenticity). A digital signature combines hashing and public key cryptography. On the sending side, a server in domain.com hashes the message to make its fingerprint, encrypts the fingerprint with the domain's private key, and adds the result to the email as a signature header. It can happen on any server, as long as it is before the mail leaves the domain. The receiver needs the matching public key, and DNS is what distributes domain information, so domain.com publishes it in a DNS TXT record. On the receiving side, the server reads the signature, fetches the public key, decrypts the signature, makes its own hash of the message and compares the two. Matching fingerprints mean the mail is unchanged and was signed with domain.com's private key. ("The private key encrypts the hash" is the lesson's simplified way to say "signs".)

What you'll learn

Identify who does each step of DKIM: the sending server hashes and signs, the domain's DNS publishes the public key, the receiving server verifies
Explain how DKIM's signature gives the receiver integrity and the authenticity of the sending domain

Aligned to

CompTIA Security+

4.5 Given a scenario, modify enterprise capabilities to enhance security.

Key terms

DomainKeys Identified Mail: DomainKeys Identified Mail is an email authentication mechanism that uses asymmetric cryptography to sign outgoing messages, allowing receivers to verify that the email was not altered in transit and originated from an authorized sender.
Digital Signature: A cryptographic mechanism used to verify the authenticity and integrity of a digital message or document.
Hash Function: A mathematical algorithm that converts input data of any size into a fixed-size output value used to verify data integrity.
Public Key: A cryptographic key that can be shared openly and is used to encrypt data or verify digital signatures.
Private Key: A secret cryptographic key used in asymmetric encryption to decrypt data or create digital signatures.

Topics

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