Encrypting vs. Signing with OpenPGP. What’s the Difference?

Many businesses are responsible for maintaining large amounts of confidential data, including customer records, medical records, financial reports, legal documents, and much more. It’s very common for these types of information to be transmitted via email. So how can you ensure confidential data transmitted via email is kept private? How can you ensure the integrity of transmitted data and that a message actually came from its purported sender?

Businesses need to ensure confidentiality, data integrity, message authentication (proof of origin), and non-repudiation (proof of content and its origin). These goals can be accomplished using MDaemon’s OpenPGP message encryption and signing services. Read on to learn more about the differences between encrypting and signing, and when each is used.

The Need for Encryption

Businesses need to protect sensitive data and preserve confidentiality and privacy. Whether you work in healthcare, finance, legal, HR or education, chances are you’re familiar with the terms GDPR, HIPAA or FERPA (among others). Businesses that fail to meet these regulations risk data breaches that can lead to lost revenue or legal action, as well as steep fines. To address these issues, businesses can use encryption to make their sensitive data unreadable to unauthorized parties.

The Need for Signing

In addition to data privacy, businesses may need to ensure that a message was not altered during transit, and that it actually came from the purported sender. These tasks are accomplished with message signing (adding a digital signature) using OpenPGP. Much like your handwritten signature, a digital signature can be used for authentication purposes, but also cannot be forged.

Signing a message helps ensure the following:

  • Data Integrity – That the message was not altered from its original form.
  • Message Authentication (Proof of Origin) – That the message actually came from the purported sender.
  • Non-repudiation – That the sender cannot deny the authenticity of the message they sent and signed with OpenPGP.

Encrypting vs. Signing – What’s the Difference?

So what are the differences between encrypting & signing? Let’s discuss each.

What is Encryption?

Encryption is the act of converting plain text to cipher text. Cipher text is basically text that has been scrambled into non-readable format using an algorithm – called a cipher. MDaemon’s implementation of OpenPGP encryption uses public key encryption (also known as asymmetric key encryption) to encrypt email messages and attachments.

So How Does Public Key Encryption Work?

Public key encryption uses public/private key pairs. If you want me to send you an encrypted message, you send me your public key, which I import into my encryption software (using the OpenPGP configuration screen in MDaemon, in this case). I encrypt the message with your public key. When you receive the message, you decrypt it with your private key. Even though your public key can be freely distributed and used to encrypt messages addressed to you, these encrypted messages can only be decrypted with your own private key. This private key must always be kept secret. Data encrypted with the public key can only be decrypted with its corresponding private key; conversely, data encrypted with the private key can only be decrypted with its corresponding public key. We’ll talk about why you would encrypt a message with your own private key in the next section when we discuss message signing.

Encrypting email with OpenPGP
Encrypting email with OpenPGP

In our latest release of MDaemon, we’ve added the ability for MDaemon Webmail users to encrypt messages from within the message compose window. This procedure is explained in this blog post.

Check out the following video to see this process in action!

Encrypting a message helps ensure that the message is kept confidential. The message remains in its encrypted format until it is decrypted with the recipient’s private key.

What is Message Signing with OpenPGP?

As I mentioned above, messages are encrypted with the message recipient’s public key and decrypted with the corresponding private key. Message signing, on the other hand, uses the sender’s private key to sign (encrypt) the message, and his public key is used to read the signature (decrypt). Message signing binds the identity of the message source to the message. This helps ensure data integrity, message authentication, and non-repudiation.

For example, if John wants to digitally sign a message to Michelle, he uses his private key to encrypt the message, and sends it (along with his public key if it hasn’t already been sent) to Michelle. Since John’s public key is the only key that can decrypt the message, the digital signature is verified by simply decrypting the message with John’s public key.

Signing with OpenPGP
Signing an Email Message with OpenPGP

Signing a message with OpenPGP ensures that the message was not altered in transit, that it did in fact come from the purported sender, and that the sender cannot deny the authenticity of the message they sent and signed with OpenPGP.

More information on using MDaemon’s PGP encryption & signing features can be found in the following knowledge base article:

How to enable MDaemon PGP, configure who can use MDPGP, and create keys for specific users

http://www.altn.com/Support/KnowledgeBase/KnowledgeBaseResults/?Number=1087

Do you have questions? Let us know in the Comments section below!

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The Recent Concerns with OpenPGP and S/MIME Encryption

On Monday, May 14th, the Electronic Frontier Foundation (EFF) reported that European researchers had discovered core problems and commonplace implementation flaws in the S/MIME and OpenPGP protocol specifications. The vulnerability, which the researchers have described as EFAIL, can reportedly expose the content of encrypted emails (even messages sent in the past) to be viewed. The EFAIL vulnerability affects many email clients that use S/MIME and OpenPGP. There is a list of email clients with vulnerabilities by protocol in an article posted at thehackernews.com.

It’s very important to understand that to be at risk for this vulnerability, attackers would need access to your emails. This means that your email system has been compromised by an attacker who has access to the encrypted emails through tactics such as eavesdropping on network traffic (also known as a man-in-the-middle (MITM) attack), compromised email accounts, access to email servers, backup systems or client computers, usually achieved through social engineering attacks, such as Phishing and other tactics.

We have checked our own web-based email client (MDaemon Webmail) and our MDaemon OpenPGP-based encryption feature. Our results show that MDaemon Webmail is not vulnerable. However, the MDaemon email server OpenPGP feature is partially vulnerable to one implementation flaw. We have released a patch for affected versions of MDaemon email software, which can be found here. The current version of the MDaemon email server, v18.0.1, includes this fix.

A Reminder on the Best Email Security Practices

This latest issue should remind us all about the importance of email security practices as a whole.  Implementing strong passwords, two-factor authentication, location screening, SSL/TLS, SMTP AUTH, IP Shielding, dynamic screening, freezing accounts after failed authentication attempts, all play a role in helping to keep your accounts and your email safe. You can review a list of email security features in MDaemon here.

If you’ve implemented security to help protect malicious people from accessing your email accounts, then you are less likely to have an account compromised and you will be better protected against these types of attacks and vulnerabilities.

Ongoing Monitoring

While the researchers go into some depth to expose issues deep within the S/MIME and OpenPGP specification documents, these encryption protocols may need specification changes to address the longer-term issues mentioned in the initial report. MDaemon Technologies will continue to monitor this issue.

Additional Resources

We have provided links to past blog posts that cover a number of email security topics to provide additional information:

Thwart Hackers with Strong Password Policies

Are You Taking the Security of Your Email Account Seriously?

Why Passwords May Not Keep Your Email Safe

Block Incoming Connections by Country with MDaemon’s New Location Screening Feature

SSL & TLS Best Practices

Block Hackers from Guessing Passwords with MDaemon’s Improved Dynamic Screening

Are You Doing Enough to Protect Your Email Privacy?

Follow These 13 Tips to Avoid Being Blacklisted

New Security & Collaboration Features for MDaemon 17.5!

Introducing SecurityGateway 5.0, with New Location Screening, Terms of Service Agreements, and More!

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