Complete Guide to File Encryption When Sending via Email

Effective Methods for File Encryption When Sending via Email

For encrypting files when sending via email, there are several effective methods: using archivers with built-in encryption, specialized encryption programs, as well as cloud services with secure file transfer functionality. The most popular approaches are password-based encryption, asymmetric encryption with public keys, and combined methods that provide maximum data protection during transmission.

Table of Contents

• Basic Encryption Methods
• Programs for Encrypting and Sending Files
• Methods for Secure Key Transfer
• Protection with Compromised Email Account
• Practical Recommendations for Choosing a Method
• Free Encryption Solutions

Basic Encryption Methods

Password-Based Encryption

The simplest and most common method is creating password-protected encrypted archives. Most archivers (7-Zip, WinRAR, WinZip) support encryption using AES-256, Blowfish, and other algorithms. The file is first archived and then encrypted with a strong password.

Advantages: Easy to use, widely supported by programs
Disadvantages: Depends on password strength, key is transmitted with the file

Asymmetric Encryption

Uses a pair of keys - public and private. The sender encrypts the file with the recipient’s public key, which can only be decrypted with their private key. Algorithms like RSA, ECC are suitable for implementation.

Advantages: High security, encryption key doesn’t need to be transmitted
Disadvantages: Complex setup, both parties need to have keys

Symmetric Encryption

Uses a single key for both encryption and decryption. AES, Blowfish, 3DES algorithms provide reliable protection provided the key is securely transferred.

Advantages: Fast performance, simple implementation
Disadvantages: Requires secure key transfer between parties

Programs for Encrypting and Sending Files

7-Zip

A free archiver with strong AES-256 encryption support. Allows creating encrypted .7z and .zip archives.

# Example command for file encryption
7z a -p"strong_password" -mhe=on -mem=AES256 encrypted_archive.7z important_file.docx

VeraCrypt

Creates encrypted volume containers that can be sent as regular files. Supports multiple encryption algorithms.

GPG (GNU Privacy Guard)

A powerful tool for asymmetric encryption based on the OpenPGP standard.

# Encrypting a file using the recipient's key
gpg -r recipient@example.com --encrypt --armor important_file.docx

AxCrypt

Simple interface for file encryption using AES-256 algorithm. Integrates with Windows Explorer.

Methods for Secure Key Transfer

Separate Key Transmission

The most secure method is to send the encrypted file and the decryption key through different communication channels. For example, the key can be transmitted by phone, in a messenger, or in person.

Important: The key should never be sent together with the file in the same email

Using Passphrases

Instead of complex keys, you can use easily memorable passphrases that are transmitted separately from the file.

Key on Different Platforms

The key can be sent through another email system, messenger, or even written on paper.

Protection with Compromised Email Account

Multi-Factor Authentication

Provide additional protection for your email account using SMS codes, authentication apps, or biometrics.

Temporary Passwords

Use one-time passwords or temporary links for accessing files with a limited lifespan.

Client-Side Encryption

Apply encryption before uploading the file to the email service servers. This ensures that even if the server is compromised, the data remains protected.

Digital Signatures

Add digital signatures to files to verify their authenticity and integrity.

Practical Recommendations for Choosing a Method

For Personal Documents

Use 7-Zip or VeraCrypt with a strong password (minimum 12 characters, including letters, numbers, and special characters).

For Business Correspondence

Prefer GPG or PGP for asymmetric encryption with digital signatures.

For Large Files

Combine encryption with compression and use cloud services with secure transfer (WeTransfer, SendSafely).

For Mass Distribution

Consider using corporate encryption systems with centralized key management.

Free Encryption Solutions

Standard Tools

• 7-Zip - free archiver with AES-256
• VeraCrypt - creating encrypted volumes
• GPG4Win - encryption tools suite for Windows
• OpenSSL - command-line utility for file encryption

Web Services

• ProtonMail - secure email service with encryption
• Tutanota - ProtonMail alternative with open source code
• Firefox Send - secure file transfer (though being discontinued)
• WeTransfer - file transfer with password protection

Mobile Applications

• Signal - message and file encryption
• Session - decentralized encryption
• AxCrypt - simple encryption for mobile devices

When choosing an encryption method, always consider data confidentiality, implementation complexity, and convenience for the recipient. For maximum security, it’s recommended to combine multiple protection methods.

Sources

1. Official 7-Zip Documentation
2. VeraCrypt - Official Project Page
3. GNU Privacy Guard - User Guide
4. NIST Guide to Secure File Transfer
5. OWASP Encryption Algorithm Comparison

Conclusion

• Choose an appropriate encryption method based on data type and required security level
• Always transmit keys separately from encrypted files through different communication channels
• Use modern encryption algorithms - at least AES-256 for symmetric and RSA-2048 for asymmetric encryption
• Regularly update encryption software and monitor for vulnerabilities in the tools used
• Train recipients on proper handling of encrypted files and keys

For additional protection, it’s always recommended to combine multiple security methods and regularly review your practices for transmitting confidential information.