DomainKeys Identified Mail, or DKIM, is a technical standard that helps protect email senders and recipients from spam, spoofing, and phishing.  It is a form of email authentication that allows an organization to claim responsibility for a message in a way that can be validated by the recipient.

Specifically, it uses an approach called “public key cryptography” to verify that an email message was sent from an authorized mail server, in order to detect forgery and to prevent delivery of harmful email like spam. It supplements SMTP, the basic protocol used to send email, because it does not itself include any authentication mechanisms.

How does it work?

It works by adding a digital signature ke headers of an email message. That signature can be validated against a public cryptographic key in the organization’s Domain Name System (DNS) records. In general terms, the process works like this:

Pemilik domain menerbitkan kunci publik kriptografi sebagai catatan TXT yang diformat secara khusus di dalam keseluruhan catatan DNS domain.

When a mail message is sent by an outbound mail server, the server generates and attaches a unique DKIM signature header ke message. This header includes two cryptographic hashes, one of specified headers, and one of the message body (or part of it). The header contains information about how the signature was generated.

Ketika server email masuk menerima email masuk, server akan mencari kunci DKIM publik pengirim di DNS. Server masuk menggunakan kunci ini untuk mendekripsi tanda tangan dan membandingkannya dengan versi yang baru saja dihitung. Jika kedua nilai tersebut cocok, pesan tersebut dapat dibuktikan keasliannya dan tidak diubah dalam perjalanan.

What is a DKIM signature?

A DKIM signature is a header added to email messages. The header contains values that allow a receiving mail server to validate the email message by looking up a sender’s DKIM key and using it to verify the encrypted signature. It looks something like this:

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/santai; d=sparkpost.com; s=google; h=dari:content-transfer-encoding:subjek:id-pesan:tanggal:ke:mime-version; bh=ZkwViLQ8B7I9vFIen3+/FXErUuKv33PmCuZAwpemGco=; b=kF31DkXsbP5bMGzOwivNE4fmMKX5W2/Yq0YqXD4Og1fPT6ViqB35uLxLGGhHv2lqXBWwFhODPVPauUXxRYEpMsuisdU5TgYmbwSJYYrFLFj5ZWTZ7VGgg6/nI1hoPWbzDaL9qh

Header tanda tangan DKIM mengemas banyak informasi, karena dimaksudkan untuk pemrosesan otomatis. Seperti yang dapat Anda lihat dalam contoh ini, header berisi daftar bagian tag=nilai. Tag yang penting termasuk "d=" untuk domain penandatanganan, "b=" untuk tanda tangan digital yang sebenarnya, dan "bh=" untuk hash yang dapat diverifikasi dengan menghitung ulang menggunakan kunci publik pengirim.

Tanda tangan pada dasarnya unik dari satu pesan ke pesan lainnya, tetapi elemen-elemen dasar ini akan ada di setiap header tanda tangan DKIM.

How is it related to SPF, DMARC, or other standards?

DKIM, SPF, dan DMARC merupakan standar yang memungkinkan berbagai aspek autentikasi email. Semua standar ini menangani masalah-masalah yang saling melengkapi.

• SPF allows senders to define which IP addresses are allowed to send mail for a particular domain.

• DKIM menyediakan kunci enkripsi dan tanda tangan digital yang memverifikasi bahwa pesan email tidak dipalsukan atau diubah.

• DMARC unifies the SPF and DKIM authentication mechanisms into a common framework and allows domain owners to declare how they would like email from that domain to be handled if it fails an authorization test.

Apakah saya memerlukan DKIM?

If you are a business sending commercial or transactional email, you definitely need to implement one or more forms of email authentication to verify that an email is actually from you or your business. Properly configuring email authentication standards is one of the most important steps you can take to improve your deliverability. However, by itself it only goes so far; SparkPost and other email experts recommend also implementing SPF and DMARC to define a more complete email authentication policy.