What file encryption is and how to encrypt files on any device

What is file encryption?

File encryption is a method of converting readable data (plaintext) into scrambled, unreadable content (ciphertext) using an algorithm and an encryption key. Only someone with the right key can decrypt and access the original file.

This method is different from communication encryption (e.g., secure messaging apps) or database encryption. File encryption is specific to stored content: documents, images, videos, and spreadsheets.

An encrypted file becomes a locked box. Without the key, it's gibberish.

Types of encryption algorithms used for files

Encryption isn't one-size-fits-all. The most common file encryption methods you'll come across include:

• Symmetric encryption uses the same key to encrypt and decrypt the file. It's fast and efficient, which makes it a good choice when you need to encrypt large amounts of data. AES (especially AES-256) is the current industry standard, while DES was used in the past but is no longer considered secure.
• Asymmetric encryption uses two keys: a public key to encrypt and a private key to decrypt. It's slower than symmetric encryption but better for things like secure key exchange, digital signatures, or encrypted emails. RSA and ECC (elliptic curve cryptography) are two of the most widely used methods.
• Hybrid encryption combines the two methods. For example, OpenPGP encrypts the actual file with symmetric encryption, then wraps the key using asymmetric encryption. This approach is common in secure email and File Transfer Protocol (FTP) sites — it's efficient and keeps the keys safe.
• Hashing (not actually encryption) creates a one-way output and can't be reversed. It's useful for verifying integrity (e.g., checking if a file was tampered with), but it doesn't protect data like encryption does. In the context of hashing vs. encryption, hashing ensures data integrity by producing a fixed-size fingerprint, while encryption securely transforms data so it can be reversed only with the correct key.

Why is file encryption important?

Whether you're backing up personal files or handling sensitive business data, encryption keeps your information from falling into the wrong hands.

Protecting your personal data

You don't need to be a celebrity or CEO to be a target of data theft. Everyday personal data is valuable to hackers, scammers, and sometimes even people close to you. Encryption helps you keep control because it:

• Prevents identity theft if your laptop or phone is lost or stolen.
• Secures sensitive files like tax returns, ID scans, or private messages.
• Keeps snoops (from nosy roommates to hackers) out of your stuff.
• Adds an extra layer of security when sharing files online.

Meeting compliance and business requirements

If you're handling customer, employee, or financial data, encryption is the law — regulations like the GDPR, HIPAA, and PCI DSS require it. Using encryption provides multiple critical benefits for your business, including:

• Helping you avoid fines, lawsuits, and embarrassing data breaches.
• Ensuring sensitive data stays protected during transfers or storage.
• Making your business more resilient to cyber threats.

How does file encryption work?

File encryption sounds complex, but the core process is pretty straightforward. It turns readable data into unreadable code and then back again.

What happens behind the scenes:

1. 1.You choose a file to encrypt.
2. 2.An encryption algorithm scrambles its contents into ciphertext, unreadable to anyone without the key.
3. 3.You or the system stores a decryption key.
4. 4.When needed, that key unlocks the encrypted data and restores it to its original state.

Encryption strength depends on the algorithm, key length, and randomness. AES-256, for example, is considered nearly uncrackable with today's tech.

How to generate and protect encryption keys

The strength of your file encryption depends heavily on the quality and security of your encryption key. It's the digital key to the locked vault — if it's weak, lost, or stolen, your encryption is basically useless.

Follow these tips to generate and protect a strong encryption key:

• Use randomness. Never rely on guessable passwords — create strong keys with secure random number generators instead.
• Store it safely. Use encrypted key vaults, password managers, or physical devices (like YubiKeys or hardware wallets).
• Don't reuse keys. Generate a new encryption key for each critical system or use case.
• Rotate it regularly. For long-term security, rotate keys on a set schedule.
• Back it up securely. Losing access to your encryption key means losing access to your data. Keep a secure backup offline or in a safe location.

Which files need to be encrypted?

You should secure files that you don't want to be viewed by outside eyes, including:

• Personal files. Photos, private videos, ID scans, tax returns, medical info, saved login details.
• Business files. Contracts, client records, HR documents, financial reports, proprietary data.

Also, consider encrypting:

• Backups and anything stored in the cloud.
• Metadata (file names, sizes, timestamps), especially in sensitive environments.
• PDFs, voice notes, synced notes, and other "miscellaneous" files people often forget about.

When deciding whether to encrypt your files, just ask yourself, "How would I feel if a stranger stole and viewed this file?" If that's something you wouldn't want to happen, encryption is a good idea.

File encryption vs. folder encryption

Not sure whether to encrypt individual files or whole folders? It depends on what you're protecting and how you're using it.

File encryption secures one file at a time. It's useful for secure file sharing or keeping a specific document safe. Meanwhile, folder encryption covers everything inside a directory in one go.

Folder encryption makes it easier to manage large volumes and simplifies cloud storage security. However, it may be slower or use more system resources. Plus, one weak password may compromise everything.

Bottom line: Use file encryption for high-risk items and folder encryption for broader coverage.

Limitations and risks of file encryption

Encryption is powerful, but it's not a silver bullet. Watch out for these limitations:

• Slower performance. Large encrypted files can take longer to open, especially on older hardware.
• Human factors still matter. Encryption won't stop phishing, social engineering, or someone guessing your weak password.
• Lost keys mean lost data. If you forget or misplace your decryption key, there's no recovery button. The data's gone.
• Metadata isn't always protected. File names, sizes, and timestamps can still leak info if not encrypted separately.
• Compatibility issues. Some tools don't translate well across platforms or systems. What you encrypt on Windows may not open cleanly on Mac or Linux.

How to encrypt files on your device

Whether you're securing one document or a full folder, the basic steps are the same:

1. 1.Choose your file(s) or folder(s). 
2. 2.Pick your encryption method or software.
3. 3.Use a strong, unique password or key.
4. 4.Store the key securely.
5. 5.Test decryption before deleting originals.

Below are quick guides for each major operating platform.

Linux file encryption

If you're working from the Linux command line, gpg is a simple and reliable tool for individual files.

To encrypt a file, type: gpg -c filename

You'll be prompted to create a passphrase. This creates a new encrypted file with a .gpg extension.

To decrypt it later, type: gpg filename.gpg

For encrypting folders or setting up encrypted volumes, tools like VeraCrypt, ecryptfs, or Cryptsetup with LUKS are more robust. Each tool has its own setup, but most support strong encryption standards like AES-256 and integrate well with Linux desktop environments.

Windows file encryption

If you're using Windows Pro, Enterprise, or Education, you have built-in encryption through the Encrypting File System (EFS). It's a quick way to protect files without installing anything extra:

1. 1.Right-click on the file or folder you want to encrypt.
2. 2.Select "Properties" from the context menu.
3. 3.In the "General" tab, click "Advanced."
4. 4.Check "Encrypt contents to secure data."
5. 5.Click "Ok" and then "Apply."
6. 6.Choose whether to encrypt just the selected item or its parent folder as well.
7. 7.Confirm with "Ok" to finish.

Once encrypted, the file is tied to your Windows user account. Only you or someone with your login credentials can open it. Just make sure to back up your encryption certificate in case you ever need to recover the files on another device.

Mac file encryption

MacOS offers built-in encryption options through FileVault and Disk Utility.

Using FileVault for full disk encryption

FileVault encrypts everything on your Mac's startup disk and keeps it locked behind your login password:

1. 1.Go to "System preferences"> "Privacy & security"> "FileVault."
2. 2.Click "Turn on FileVault."
3. 3.Choose how you want to unlock your disk and set a recovery option.
4. 4.Wait for the encryption process to complete (this may take several hours).

Encrypting individual files or folders with Disk Utility

Need to encrypt just one folder? Disk Utility can create a protected disk image:

1. 1.Open Disk Utility from "Applications"> "Utilities."
2. 2.Go to "File"> "New image"> "Image from folder."
3. 3.Select the folder you want to encrypt and click "Choose."
4. 4.Set an encryption level (128-bit or 256-bit AES).
5. 5.Create and verify a password for the encrypted image.
6. 6.Pick a location and save the encrypted disk image.

To open it later, double-click the image and enter your password — it will mount like a regular folder.

Android file encryption

Most newer Android devices have encryption enabled out of the box, especially if you're running Android 10 or later. But if you're using an older device, you may need to turn it on manually.

To check or enable encryption:

1. 1.Go to "Settings" > "Security."
2. 2.Tap "Encrypt phone" or "Encrypt tablet" (this step may vary by manufacturer).
3. 3.Follow the on-screen instructions and make sure your device is fully charged or plugged in.

Note: On modern Android phones, file-based encryption is automatic once you set a screen lock (PIN, pattern, or password).

iOS file encryption

All iPhones and iPads are encrypted by default as long as you've set a passcode. That passcode ties directly to the encryption key.

To check:

1. 1.Go to "Settings"> "Face ID & passcode" (or "Touch ID & passcode").
2. 2.Set a strong passcode if you haven't already.

What is automated file encryption?

Automated file encryption encrypts files in the background without you having to think about it. It's built into many cloud platforms, enterprise systems, and secure email tools, and usually kicks in the moment a file is saved, uploaded, or shared.

Why it matters:

• Happens in real-time (e.g., when saving to the cloud)
• Keeps security consistent across users and teams
• Helps meet compliance requirements automatically
• Reduces human error

You'll find this in tools like Dropbox Business, Google Workspace (with proper settings enabled), and NordLocker, which handles both cloud and local encryption automatically.

Encryption software examples

Not all file encryption software is created equal. Whether you're locking down personal documents or securing sensitive business files, the right tool depends on your needs.

What is the best way to encrypt a file?

No universal "best" method exists — it all depends on what you're encrypting, how often you need to access or share it, and who else needs access.

For beginners:

• Password-protected ZIP files. Easy, free, and supported on most devices. Good for quick one-off encryption.
• Built-in OS encryption (like FileVault). Great for securing everything on your device, but not ideal for individual file sharing.
• Cloud protection. When storing files in the cloud, use services like NordLocker cloud storage that offer end-to-end encryption or encrypt files before uploading.

For business use:

• Encrypted volumes or drives. Use tools like VeraCrypt for securing large amounts of data or external storage.
• Secure cloud storage. NordLocker Business is built for teams that need secure storage and sharing without the tech hassle.
• Public-key encryption (e.g., GPG). Best for secure file sharing in technical environments, but not user-friendly.
• Managed enterprise solutions. Ideal for larger organizations that need centralized control, compliance reporting, and key management.

What is the best way to send encrypted files?

Now that your data is locked down, the next step is encrypted file sharing — getting those secure files to the right person without exposing them in transit.

A few smart ways to do that:

• Use password-protected cloud links from services offering cloud storage that puts privacy first (e.g., NordLocker or Proton Drive).
• Choose end-to-end encrypted apps (the most secure messaging apps include Signal, Wire, and Wickr).
• Share passwords separately — never in the same message. Use a phone call, a separate app, or a secure password manager.
• Use the NordPass password generator to create and store strong passwords securely.

Real-world use cases of file encryption

Encryption is useful in everyday life and across all kinds of jobs. Here's where it makes a real difference:

• Protect personal memories. Family photos, videos, and journals deserve more than a basic cloud upload. Encrypt them before syncing or sharing.
• Secure financial and identity documents. Tax returns, pay stubs, ID scans — all of these can be exploited and should be encrypted.
• Keep client files confidential. You should encrypt anything involving sensitive client info (like contracts, invoices, or project drafts).
• Stay safe while working remotely. Encrypt work files before sending them or saving to shared folders, especially if you're on public Wi-Fi or using your personal device.
• Stay on the right side of the law. If you handle customer, employee, or patient data, encryption helps you meet privacy regulations like the GDPR and HIPAA without overthinking it.