Frequently Asked Questions

The file aescrypt.exe is the command-line version of AES Crypt. It is intended to be run inside the "Command Prompt" (or PowerShell) window. What you are probably looking for is the context menu that has the "AES Encrypt" and "AES Decrypt" options. See the Windows help page for how to access that menu.

Yes, as long as the password for all of the files is the same and all files are to either be encrypted or decrypted. It's not possible to mix modes. That is, you cannot encrypt some and decrypt others at the same time.

When using the desktop version of AES Crypt, just select all the files you want to encrypt or decrypt. Then, follow the same process you would follow for one file. For example, on Windows you would just right-click on one of the selected files and a menu will appear showing you the option to encrypt or decrypt. On Mac, you can drag and drop multiple files onto the lock icon, or select multiple files, right-click and choose "Open with", and then select AES Crypt.

If using the command-line version of AES Crypt, you can list multiple files to be encrypted or decrypted where you would normally enter a single filename.

Yes. AES Crypt uses the same file format and encryption methods on all operating systems, so files can be easily exchanged between people who are using AES Crypt on different operating systems.

No. Once you buy a license, you have the right to use all future upgrades to AES Crypt.

There is no fixed limit on the password length, but different operating systems may impose different restrictions. (Older versions capped this length at 1024 characters, but that limit was removed with AES Crypt v4.)

On Windows, it is now possible to have passwords about 16,000 characters long. However, using such long passwords might cause issues on other platforms and they are overkill.

If using a password generator to create random passwords, one only needs about 40 characters (if using "special characters") to yield 256 bits of entropy (randomness).

The length is perhaps more important if using passphrases (as opposed to passwords). Still, it would probably be best to restrict the total number of characters to 1024 or 2048 just to avoid issues when sharing files.

Just for a point of reference, the default length of generated key files in AES Crypt is 64 characters. This was considered sufficient, as that yields 384 bits of entropy.

No. We take privacy and security very seriously, so we do not have a backdoor in AES Crypt. Please use strong passwords but also take measures to ensure you do not lose them. There is no way to decrypt a file without the password.

Some of our customers have told us they use various password managers to store passwords. Others use tools like Single Pass to generate unique passwords for each file. Use whatever method works for you but just do not lose them!

Yes. AES Crypt can decrypt all prior versions of files created with older versions of AES Crypt. We fully intend that all future versions will likewise be able to read older files.

AES Crypt will only create files using the latest stream format. This approach makes AES Crypt easier to use, but also ensures new files employ the latest encryption methods.

No. For security reasons (and private network considerations), AES Crypt has no ability to communicate over the Internet.

To get notified about updates to AES Crypt, you can subscribe to the AES Crypt mailing list or, if you use RSS, subscribe to the AES Crypt discussion forum.

For an individual (including individual employees), no. Individuals with a license can install and use the software on all of their computers, including different operating systems.

For businesses that use AES Crypt on servers, each server must have a distinct license. A common use for servers running AES Crypt is facilitate secure, automated backup of a server where the encrypted backup file gets pushed to cloud storage or stored on external storage media.

No, AES Crypt will never delete a file one is encrypting or decrypting. There are two significant reasons for this.

The first reason is simply that people sometimes make mistakes by encrypting or decrypting the wrong file. We don't want to destroy the original file, causing frustration.

The second reason, and very importantly, is that deleting files on modern solid state storage (SSDs, SD cards, USB drives, etc.) doesn't actually delete the file. What drive controllers do is just "mark" the data as erased. The only way to truly erase data on such devices is to erase the entire drive. Doing that, though, can cause excessive wear and tear to storage devices. We do not want to lend to the illusion of security by merely "marking" data as deleted, which is effectively what happens with modern storage devices.

The concept of a "key file" in AES Crypt is actually pretty simple: it is merely a password stored in a file. The primary purpose is for use on servers that perform automated backups.

To create a key file, the AES Crypt command-line tool can be used like this:

aescrypt -g -k secret.key -s 128

This command instructs AES Crypt to generate a cryptographically random key stored in "secret.key" and having 128 characters in length. (The default length is 64, which yields 384 bits of entropy and would be sufficient.)

If you wish to create a key file manually, store the password in a UTF-8 encoded file (without a BOM) or a UTF-16 encoded file (with a BOM). AES Crypt can read those file formats and properly extract the characters.

Having the password stored in a cleartext file is risky, so key files need to be kept private. The directory storing key file(s) or the key files themselves should have permissions set such that only the authorized user can access the key file.

Since key files are often used as part of a backup strategy, copies of the key files should be securely stored outside the machine so that data can later be decrypted.

AES Crypt uses 256-bit encryption using the Advanced Encryption Standard (AES) using cipher block chaining (CBC) mode.

Data integrity is ensured by using HMAC-SHA256 as a message authentication code (MAC) function.

Passwords are transformed into a usable key using the key derivation function (KDF) PBKDF2 using 300,000 iterations and HMAC-SHA512 as the hashing function.

Each of the algorithms and choices adhere to FIPS recommendations.