WHAT IS S/MIME OR ENCRYPTED EMAIL? How Does It Work?

As you read this blog, there’s a good chance your computer or smartphone has Gmail open in another tab. And it’s no surprise! Email is one of the most widely used and essential forms of communication, with over 4 billion users.

Due to such large numbers, it is one of the most exposed and vulnerable medium that can be easily altered, forged, or intercepted by malicious actors. As per the data, 75% of the businesses suffered successful email attacks in the year 2023, and $1,000,000 was the cost of email attacks in 2022.

With such facts and figures, how can one protect email messages from being tampered with and impersonated? The answer is S/MIME or encrypted mail.

Here in this blog, we are going to explain everything about S/MIME so you can use it for email security.

What is S/MIME?

Secure/Multipurpose Internet Mail Extensions, or S/MIME, is a robust protocol that enables you to sign and encrypt your email messages using public key cryptography.

This encryption serves as a shield for your business emails, ensuring their security and authenticity.

It also allows individuals to digitally sign their emails, providing a clear indication of the sender’s identity. In the past years, S/MIME has gone through several changes to remove security weaknesses, such as EFAIL, which affects end-to-end encryption solutions such as PGP and S/MIME.

Other than the usability aspect, here are some features of S/MIME:

• End-to-end encryption escalates data privacy as only the recipient and sender can access the data.

• Encryption offers higher security levels for the data inside the email.

• Digital signatures ensure that no one has altered attachments and message contents.

• The digital signature proves that the sender is who they say they are.

Also Read: Email Security Best Practices to Safeguard Email and Email Server

How Does S/MIME Work?

Based on the principle of PKI, also known as Public Key Cryptography, it uses two keys: Private Key & Public Key

The private key decrypts and unlocks the messages, and the public key encrypts or locks the messages. The private key is kept secret by the owner, and you can share the public key with anyone.

Also Read: What is Secure Email SSL Certificate with Digital Signature?

S/MIME utilizes digital certificates via PKI, which are digital documents that hold the public key and information about the owner, such as email address, name, and organization. Certificate authorities issue and verify certificates from trusted third parties and help establish the trust and validity of public keys and identity.

A S/MIME certificate permits you to sign your emails using hashing, the exact way you use a digital signature to maintain your identity. The private key utilizes your sign to email from the point you sign and send it. And when the recipient gets the email, a public key applies to verify the digital signature.

This way, it makes sure that the email you receive is from the original owner and not from someone else pretending to be you. Such assurance is vital when you are dealing outside the organization.

The process of digital signing of an email is as follows:

• After creating and before sending the email, sanction a digital sign to generate a hash for the message.
• The use of a private key to encrypt the hash will result in the digital signature. 
• The public key and digital signature are attached to the message when sent.
• The recipient can verify the sender from the public key and, using that, verify if the hash matches with the content. This will be a great help in providing integrity and identity to the sender.

Caution: The message has been altered if the hash does not match. So, make sure to check it.

The process of encrypting an email with S/MIME is:

• Either by a directory service or by exchanging digitally signed email, the sender gets the recipient’s public key.
• Using a symmetric algorithm, the sender then translates the message to ciphertext.
• After sending the encrypted key and ciphertext as a package file, it gets decrypted with the recipient’s private key.
• The recipient then receives the package and checks the digital signature and sender’s certificate using a hash function and public key. The message is authentic and intact if the verification is successful.
• With their private key, the recipient decrypts the ciphertext using the same symmetric encryption algorithm.

How does S/MIME Protect an Email?

A digital signature ensures that transmitted data is confidential and authentic to its sender. S/MIME safeguards an email by following method:

Email Encryption

The moment the sender hits the send button, the email content gets encrypted using the recipient’s public key. Even if the email gets hacked by a hacker, they cannot view the content unless they have a private key.

Digital Signature

Along with encryption on installing the certificate, the email will get digitally signed. Authenticated by the public key of the recipient and private key of the sender, emails get signed. An untouched digital signature shows that the email content has not been tampered with.

Data Confidentiality

Email content encryption ensures the confidentiality of the data and attachments sent through the email. If anyone attempts to view the email content, it remains void, as someone can only decrypt the data with the private key unique to the recipient.

Signature Authentication

As the sender digitally signs the email with the help of a private key, the recipient authenticates and validates the signature using a public key to make sure the email received is from a trustworthy source.

Content Integrity of the Email

When the recipient emails get validated using the public key of the recipient, they are guaranteed the absence of any alteration in the email content and are authentic as and when sent.

Authenticity by the Sender

The digital signature is unique and is assigned to the domain when the S/MIME certificate is installed and purchased. This provides the authenticity of the signature by the sender for any legal proceedings.

Uses of S/MIME

S/MIME ensures that your email has not been tampered with by any third party. It creates digital signatures to sign and encrypts all your emails. Along with that, it verifies the email client you use.

Some of the uses of S/MIME are:

Document Signing

Similar to email signing, you can use S/MIME certificates for document signing as well. With the use of a private key, sign your documents digitally. By using a digital signature, the recipient will be able to check if you signed the document and it has not been tampered with.

If, in any case, someone hacks the document you sent, the recipient will immediately receive a warning message.

Client Authentication

Client authentication helps users secure apps, networks, and servers using certificate-based two-factor authentication. With this, you can grant authentication to apps and servers to only verified users. The users with installed client certificates will be able to access servers and data. As passwords get easily cracked, so securing your server with that is not an appropriate idea.

To secure your server and data S/MIME certificate with client authentication is a great idea.

Why does your Company need S/MIME Protection?

Data breaches and tampering with your important data are pretty common these days. So, to protect your client’s data, a S/MIME installation is beneficial. Here are some points that will help you understand why your company needs S/MIME protection-   

Phishing and Spoofing

Phishing and Spoofing mainly occur by the sender’s impression. The digital signature using S/MIME authenticates and validates the sender’s identity and prevents you from security breaches like hacking and tampering. Hence, it is crucial to encrypt and sign the emails digitally.

Access to Confidential Data

Email is a vital medium for sharing sensitive information, transaction emails, business quotes, and other personal data, so make sure that email is end-to-end encrypted. Other than intended recipients, S/MIME encrypted emails are difficult to decrypt, which ensures the privacy of shared data.

Email Tampering

The email encrypted with the help of the private key of the recipient can only decrypted by the intended recipient. Hence, the S/MIME encrypted emails can stopped by the hackers, but the content is not visible.

How To Send S/MIME Encrypted Emails in Gmail?

For each sender you add to your email while composing, Gmail will display the level of encryption. To check whether the message you are sending is encrypted or not, here are a few steps:

• Compose a message.
• In the ‘To’ field, add recipients.  
• To the right of the recipient’s name, check the icons. A lock icon appears that shows the level of encryption supported by the recipient. If multiple recipients have different levels of encryption, the lowest standard encryption will be visible.
• Click on the lock and then select View Details to check and change your S/MIME settings.

Along with that, you can check the encryption status by opening the incoming message. Depending on your browser or device, steps may change.

• For Android: Click View Details and go to View Security Details.
• For iPhone: Tap View details

You will see a color-coded lock icon that shows the level of encryption the email is using. The green lock shows strong encryption apt for sensitive data, gray locks show encryption apt for common messages, and the red icon shows a lack of encryption.

While S/MIME implementation offers more robust encryption, it has multiple drawbacks:

• As messages are not end-to-end encrypted, Google can easily access your emails.

• As S/MIME is not available by default, you will need a paid account and an administrator to enable it.

• Also, it will only work if the recipient has S/MIME enabled. Otherwise, you can’t send a private email to a person using a regular Gmail account.

• If you’re at high risk of surveillance, S/MIME’s centralized system of certificate authorities could be compromised.

Also Read: How to Encrypt the Emails in Microsoft Outlook and Office 365?

New S/MIME Requirements in 2023

A recent survey found that around 92% of participants experienced email security breaches over the past years. With that, in January of the year 2023, the industry leaders adopted new S/MIME requirements to uplift consistency regarding publicly trusted email signing certificate management.

Industry leaders believe that the two most essential factors for preventing network breaches are adequate employee training and digital signatures on the outbound emails, along with encryption on emails that contain sensitive information.

The CA Forum also issued the latest Baseline requirements for guidance on S/MIME certificates. The new Baseline Requirements are as follows:

• Operational practices
• Auditing
• Appropriate and inappropriate certificate uses
• Subject identity verification
• Compliance
• Subject identity validation

Buy S/MIME Certificates from CheapSSLWeb

Now that the blog is about to end, you must have understood the importance of using S/MIME certificates to protect your emails.

So, why wait further? Buy your S/MIME certificate from CheapSSLWeb starting at just 9.49$. Here’s why you should choose us:

• No hassle. Easy installation
• Automated enrollment, renewal, and revocation processes of  S/MIME certificates.
• Any query? Get 24/7 email ticketing support from our support experts via call.

The Bottom Line

Given the rise in email tampering and phishing attacks, verifying the email sender’s identity is critical to maintaining a robust security perimeter around your organization.

Considering the security advantages, using S/MIME certificates will be beneficial as it safeguards your emails from being hacked. So, it is best to be proactive by protecting your organization from hackers before they breach your data.

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