Encrypting a file or document is the easiest way to prevent other people from accessing its contents. Thus, it will be practically impossible to see what it contains unless we have the password or decryption key. In the next post, we will see what methods we can use in most operating systems to encrypt a file safely.

Before starting, it would also be interesting to clarify that encrypted files are not 100% indecipherable. A good hacker can (albeit with difficulty) bypass encryption protection. Something can happen if we save passwords and cryptographic keys in an unencrypted file or our system are infected by a keylogger. If we have precious information, the most recommended solution is to hire an encryption service in the cloud (mainly aimed at companies).

It is also advisable to make an unencrypted backup of all sensitive files if we lose the unlocked passwords. It is best to save these backups in physical storage -memory or external disk-, preferably offline.

How to encrypt a file on Android?

From Android 6.0, all Android phones and devices already come with encrypted internal memory as standard. We can always choose to encrypt the SD card as well.

Suppose we want to protect a single file. In that case, we can do so using applications such as Andrognito, which uses a 256-bit AES algorithm with military-grade encryption to safeguard the user’s files.

Download here

To encrypt a file with Andrognito, once we have installed the application, we open it and follow these 4 steps:

  • We register and enter a 4-digit PIN or unlock pattern.
  • By default the system will create a vault or “Vault“. All the files that we add to this vault will be protected and encrypted.
  • To add files to our vault we only have to click on the “+” icon and select the document by making a long press and confirming on the “OK” icon that we will see at the top right. If the encryption has been done correctly we will see a green message.
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If we later want to decrypt any of these documents, we can do it by entering the vault, clicking on the drop-down menu next to each file, and selecting “Decrypt and export“.

One of the exciting details of this application is that it saves encrypted documents in the cloud, thus freeing up storage space and allowing access to the file from any other device (as long as we use the same account, of course).

How to encrypt a file in Windows?

We have several options if we want to protect a file with important information on a Windows computer.

We can use BitLocker -the most reliable method- a tool integrated into Windows 10, but that does not allow us to encrypt files individually. We can do something with EFS (Encrypted File System), although it is not the most recommended solution if we handle very sensitive data. The third alternative is to use a dedicated program, this being the only possible solution if we have a system with Windows 10 Home Edition.

Here is a guide you can use: How to Break BitLocker Password: 13 Step Guide to Bitlocker Recovery


EFS is an encryption tool that uses Windows and allows you to encrypt both loose files and folders on NTFS drives. It is only available in the Professional, Enterprise, and Education versions of Windows.

The system works by making encrypted files only available if the person who encrypted them is logged in to the PC. Here Windows generates an encryption key which in turn is also encrypted and stored locally. It’s a simple method, but not too safe (a good hacker could punch us if he wants to). However, if all we want is to protect certain information from curious friends or family, it may be more than enough.

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To encrypt a file or folder with EFS:

  • Open the file explorer and right-click on the file we want to encrypt and select “Properties“.
  • Click on“Advanced”and activate the“Encrypt content to protect data”tab. Click on“OK”and then on“Apply”.
  • If we have only selected a Windows file, it will invite us to also encrypt the folder for greater security. If we only want to encrypt the file we mark“Encrypt only the file”and accept.
  • Then the system will recommend us to make a backup of the certificate and the file encryption key in case the system is damaged or corrupted. If we are interested, we just have to insert a pendrive, click on“Make a backup now”and follow the instructions of the assistant.

Third-party applications

Windows 10 Home users do not have the EFS utility, so it is necessary to install a program that allows us to encrypt files for these cases. One of the most efficient and easy to use in this regard is AxCrypt.

With this program, we can change the extension to any file and replace it with the extension .AXX. In this way, the file can only be opened from AxCrypt by entering the password previously used set to encrypt the document in question.

We can also use the 7-Zip program, which serves to compress files in 7z and ZIP format and encrypt them to maximum security with AES-256 encryption.

How to encrypt a document on iPhone?

Since the launch of the now distant iPhone 3GS, all mobiles with the iOS system include basic encryption at the hardware level. However, if we want to protect our encrypted files, we must protect our iPhone or iPad with an access password.

That said, if we want to encrypt any sensitive document, photo, or delicate video, we will have to install an application for this purpose, such as Folder Lock. The application works very similarly to Andrognito, hiding the files and protecting them with an access password.

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How to encrypt a file on Android, Windows, iOS, Linux, and macOS

How to encrypt a file on Linux?

If we work from a computer with Linux, we can encrypt any file or folder using the GPG command. The only way to decrypt the file and access its information is to enter the correct password.

Suppose we have the ~/Documents/Important.docx file, and we want to encrypt it.

  • First we open a terminal window and move to the folder where the file is located. In this case we would be placed in the folder “Documents“.
  • Next, we type the command “gpg -c Important.docx” (without quotation marks).
  • Now we enter a complex password and press enter. We confirm the password.
How to encrypt a file on Android, Windows, iOS, Linux, and macOS

We will see how the document has changed its extension to “Important.docx.gpg” from this moment on. If we want to decrypt it, we have to reopen a terminal, place ourselves in the folder where the file is located and write the command “gpg -c Important.docx.gpg”. The system will ask us to enter the password, and we can reaccess it without problems.

How to encrypt a file on MacOS?

AES Crypt is open-source software that allows us to encrypt any file on macOS individually. We can download it completely free from its official website HERE (it is also available for Windows, Android, and Linux).

Its operation is effortless. We only have to locate the file, drag it to the AES Crypt icon (padlock icon) that we will see in the dock menu, and enter a password. We must write down the password somewhere since there is no password recovery process.

You can also read: How to Open BitLocker Encrypted Drive on macOS: 5 Easy Steps

How to encrypt a file on Android, Windows, iOS, Linux, and macOS

Once done, the program will generate an encrypted version of the existing file. This means that we will have two versions of the same file: one encrypted and one unencrypted. Therefore, we must delete the original file or save it on a pen drive as a backup.

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