Understanding At-Rest Encryption in Email

In today's interconnected world, email remains one of the most important communication tools for businesses and individuals alike. However, traditional email is inherently insecure, with messages stored on servers in plain text where they can be accessed by service providers, hackers, or government agencies. At-rest encryption solves this problem by ensuring that your stored emails are encrypted and can only be accessed by you.

What is At-Rest Encryption?

At-rest encryption is a security method that protects data while it's stored on servers or devices. In the context of email, this means that your messages are encrypted before being stored on email servers and can only be decrypted by you using your private encryption keys. Even the email service provider cannot access the content of your encrypted messages.

Unlike traditional email services that store your messages in plain text, at-rest encryption ensures that your data remains protected even if someone gains unauthorized access to the servers where your emails are stored.

The At-Rest Encryption Process

At-rest encryption uses a sophisticated system of cryptographic keys to secure stored data. Here's how PDG Mail implements this process:

Your Keys, Your Control

The foundation of our at-rest encryption is that you control the encryption keys. We offer two secure approaches:

Customer-Generated Keys

You can generate your own encryption keys on your local machine using your preferred cryptographic tools. Once generated, you simply upload your public key to our portal. This approach ensures complete control over the key generation process and maximum security.

Portal-Generated Keys

For convenience, you can generate keys directly in our PDG Mail portal. However, we maintain our zero-knowledge principle by implementing critical security measures:

• One-time availability: Private keys are only available for download once
• Immediate deletion: Private keys are permanently deleted from our servers after download
• No server storage: We never store private keys on our infrastructure
• Customer responsibility: You must securely store your downloaded private keys

The Encryption Process

1. Key Setup: You provide or generate your encryption keys
2. Data Encryption: Your emails are encrypted with Curve25519 using your keys
3. Secure Storage: Encrypted data is stored on our servers in Hong Kong
4. Access Control: Only you can decrypt the data using your private keys
5. Zero Access: We cannot read or access your encrypted content

How Traditional Email Works (Without At-Rest Encryption)

To understand why at-rest encryption is crucial, let's first look at how traditional email storage works:

• Plain text storage: Messages are stored on servers as readable text
• Server access: Email providers can read all stored messages
• Data breaches: Stored messages can be accessed if servers are compromised
• Data mining: Content can be analyzed for advertising or surveillance
• Legal access: Governments can request access to stored messages
• Backup exposure: Server backups may contain unencrypted data

Types of Email Encryption

There are several types of encryption used in email systems:

Transport Layer Security (TLS)

TLS encrypts the connection between your email client and the email server. While this protects messages in transit, the email provider can still access the content of messages stored on their servers.

Pretty Good Privacy (PGP)

PGP is one of the most widely used standards for end-to-end email encryption. It uses public-key cryptography to ensure that only the intended recipient can read the message.

S/MIME

Secure/Multipurpose Internet Mail Extensions (S/MIME) is another standard for email encryption that's commonly used in enterprise environments.

Why At-Rest Encryption Matters

At-rest encryption provides several critical benefits for protecting your stored email data:

Data Breach Protection

Even if someone gains unauthorized access to our servers, they cannot read your encrypted messages without your private keys. This provides protection against hackers, malicious insiders, and other security threats.

Protection Against Surveillance

In an era of mass surveillance, at-rest encryption provides protection against government monitoring and corporate data collection. Your stored communications remain protected from unauthorized access.

Business Security

For businesses, at-rest encryption protects sensitive information like trade secrets, financial data, and confidential communications from competitors and cybercriminals, even if server infrastructure is compromised.

Legal Compliance

Many industries have strict requirements for data protection. At-rest encryption helps organizations meet regulatory requirements and protect customer data, even in the event of legal requests for server access.

Backup Security

Since your data is encrypted before storage, even server backups remain protected. This ensures that your communications are secure across all copies of your data.

Challenges and Limitations

While at-rest encryption is powerful, it's not without challenges:

Key Management

Managing encryption keys can be complex. Users must securely store their private keys and ensure they don't fall into the wrong hands.

User Experience

Traditional E2EE solutions can be difficult to use, requiring users to manually manage keys and certificates. Modern solutions like PDG Mail make this process seamless.

Compatibility

Not all email clients support E2EE, and different systems may use incompatible encryption standards.

How PDG Mail Implements At-Rest Encryption

PDG Mail takes a comprehensive approach to email security, implementing at-rest encryption with industry-leading cryptographic standards and a unique zero-knowledge key management system:

Curve25519 Encryption for Data at Rest

We use Curve25519 encryption for all data stored on our servers. Curve25519 is a state-of-the-art elliptic curve cryptography algorithm that provides:

• High security: 256-bit security level with resistance to various attacks
• Performance: Fast encryption and decryption operations
• Future-proof: Designed to be resistant to quantum computing threats
• Industry standard: Widely adopted by security experts and organizations

TLS 1.3 Network Security

We utilize TLS 1.3 across our entire network infrastructure for all email protocol connections:

• IMAP connections: TLS 1.3 for incoming email retrieval
• SMTP connections: TLS 1.3 for outgoing email delivery
• JMAP connections: TLS 1.3 for modern API-based email access
• Server-to-server: TLS 1.3 for communication with other email servers

TLS 1.3 provides several advantages over older versions:

• Enhanced security: Removes support for outdated cryptographic algorithms
• Improved performance: Faster handshake process and reduced latency
• Forward secrecy: Each session uses unique keys, protecting past communications
• Privacy protection: Encrypted handshake prevents traffic analysis

Multiple Encryption Layers

Our security architecture implements multiple layers of encryption to provide comprehensive protection:

• Transport encryption: TLS 1.3 for all network connections
• At-rest encryption: Curve25519 for stored data
• Key encryption: Additional encryption for key storage and transmission

Zero-Knowledge Architecture

We operate on a strict zero-knowledge principle, meaning:

• No access to content: We cannot read or decrypt your email messages
• No key storage: Private keys are never stored on our servers
• No backdoors: There are no secret methods to access encrypted data
• Legal protection: Even if legally compelled, we can only provide encrypted data

Seamless Integration

Our encryption works transparently with standard email clients, so you don't need to change your workflow to benefit from enhanced security. The encryption and decryption processes happen automatically in the background.

Client Compatibility Requirements

To use PDG Mail's at-rest encryption, you need a compatible email client that supports the encryption standards we use:

Supported Email Clients

• Mozilla Thunderbird: Full support with built-in encryption capabilities
• Apple Mail: Compatible with proper configuration
• Microsoft Outlook: Works with encryption plugins
• Other IMAP/JMAP clients: Any client supporting our encryption standards

Critical Key Management Warning

IMPORTANT: At-rest encryption means that only you can decrypt your emails using your private keys. This creates a critical responsibility for key management:

Key Backup Best Practices

To prevent permanent data loss, follow these essential practices:

• Multiple backups: Store your private keys in multiple secure locations
• Offline storage: Keep a backup on an offline device or secure storage
• Password protection: Encrypt your key backups with strong passwords
• Regular verification: Periodically test that you can access your keys
• Documentation: Keep clear records of where your keys are stored

What Happens If You Lose Your Keys?

If you lose your private encryption keys:

• No recovery possible: We cannot decrypt your emails
• Permanent data loss: All encrypted emails become inaccessible
• New keys can be created: You can generate new encryption keys for future emails
• Old data remains encrypted: New keys cannot decrypt emails encrypted with old keys
• Fresh start: You can continue using the service with new keys, but historical emails are lost

Best Practices for Using Encrypted Email

To maximize the security benefits of at-rest encryption and avoid data loss:

• Use compatible clients: Choose email clients that support our encryption standards (Thunderbird, Apple Mail, Outlook with plugins)
• Secure key storage: Keep your private keys secure and backed up in multiple locations
• Regular key verification: Periodically test that you can access your encryption keys
• Strong passwords: Protect your email account and key backups with strong passwords
• Offline backups: Keep key backups on offline devices for maximum security
• Document your setup: Keep clear records of your encryption configuration
• Test your setup: Verify that encryption is working properly before storing sensitive data

The Future of Email Encryption

As threats to digital privacy continue to evolve, email encryption is becoming increasingly important. We're seeing several trends:

• Wider adoption: More email providers are implementing E2EE
• Improved usability: Better user interfaces make encryption more accessible
• Quantum resistance: Development of encryption methods resistant to quantum computing
• Regulatory requirements: Governments are mandating stronger encryption standards

Conclusion

At-rest encryption is not just a technical feature—it's a fundamental right in the digital age. As our lives become increasingly connected online, protecting our communications becomes more important than ever.

At PDG Mail, we believe that security should be accessible to everyone, not just technical experts. Our platform makes at-rest encryption simple and transparent, so you can focus on your communications while we handle the security.

Whether you're a business protecting sensitive information or an individual concerned about privacy, at-rest encryption provides the protection you need in an increasingly surveilled world.