What Is S/MIME Encryption? How Does It Work?

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Here’s what you need to know S/MIME encryption and the way it works

The world of internet acronyms is quite weird. Some sound like they belong in the dental industry, while others sound like reptiles in Africa. Today, we’re going to talk about a term that may (or may not) sound more like some sort of performance art than an internet standard: S/MIME.

What Is S/MIME and How Does It Benefit Encryption?

But what is S/MIME encryption? S/MIME, which stands for secure/multipurpose internet mail extensions, is an email signing protocol that uses encryption to increase email security. Much like an SSL/TLS, S/MIME is also implemented using a certificate that’s known as an S/MIME certificate.

So, how does S/MIME work? An S/MIME certificate:

  1. Ensures that are read only by the intended recipients and nobody else. In technical terminology, an S/MIME certificate allows authentication of your emails so that both recipient and sender know who they’re communicating with.
  2. Encrypts and decrypts your email messages so that no unauthorized third party can see your emails.
  3. Protects your emails/documents by not allowing any unauthorized third party to tamper with the content of the emails/documents.

Do I Need an S/MIME Certificate If I Have an Encrypted Email Server?

It’s always recommended to encrypt your email servers with a digital certificate as it ensures the security of the emails in transmit and thwart attempts of man-in-the-middle (MiTM) attacks. But there’s a fundamental difference in the way email server certificates work versus how S/MIME certificates work.

Email server certificates encrypt the email communication channel, while S/MIME certificates encrypt the emails themselves. In simpler words, email server certificates encrypt emails while they’re traveling (data in transit), and S/MIME certificates encrypt emails while they sit on the server (data at rest).

So even if you have a digital certificate installed on your email server, hackers can get themselves inside your server and access your emails, which would be lying there in plaintext. That’s where S/MIME certificates come in.

How Does an S/MIME Certificate Work?

Graphic: Public key encryption

So, when you’re answering a question like “what is S/MIME?” or “what does an S/MIME certificate do?” it’s often easiest to define S/MIME certificates as the virtual versions of hand-written signatures in the sense that they help to assert identity.

Much like how we verify a document through signature, an email signed with an S/MIME certificate generates a hash, which is used to create the digital signature, which encrypts the email. The recipient confirms this signature, and then the email gets decrypted.

S/MIME certificates work on asymmetric encryption method, just the way SSL/TLS certificates do. Asymmetric encryption involves two distinct, but mathematically related keys. One of these keys is called a public key, while the other is called a private key.

So when a user sends an email, it gets encrypted with the public key. This encrypted email can only be decrypted by the private key related to the public key. This way, it authenticates the identity of the sender/receiver; and also protects email from the wrath of unauthorized entities.

S/MIME Allows You to Sign Your Emails

An S/MIME certificate also allows you to digitally sign your emails using hashing, just like you sign documents with your hand-written signature (although not in the sense of an electronic signature), to assert your identity.

Whenever you sign an email, the private key applies your digital signature to your email. And when the recipients receive the email, your public key is applied to verify the digital signature. This way, it ensures the recipient that the email was sent by you, not someone else pretending to be you. Such assurance plays a vital role not only when you’re communicating outside your organization, but also between co-workers.

Final Word

In today’s world, email is the favorite passway of cyber perpetrators to breach the network security of an organization. And there’s no stopping them once they’ve breached it. That’s why solutions such as S/MIME certificates should be implemented. While there is a minimal cost, you should view it as an investment in your organization’s security rather than a cost. And the thing about this investment is that it’s way cheaper than the costs you face if you fall victim to an email breach.

So, it’s best to be proactive and wise by protecting your organization from the dangers before they have a chance to strike.