CBC Mode Fast AES Directory Encryption/Decryption

 Czeslaw Koscielny

Wroclaw University of Applied Informatics, Poland

e-mail: ckoscielny@horyzont.eu

Abstract:

The application shows how to implement a Maple wrapper for a binary file executing the AES algorithm about 5 000 times faster than Maple implementations of this algorithm published in Maple Application Center

(http://www.maplesoft.com/applications/view.aspx?SID=6618 and http://www.maplesoft.com/applications/view.aspx?SID=7086)

How the Application Works

After opening the document the user will see the window:

Fig. 1. Application window

It is possible now to select the AES key length (128, 192 or 256 bits), to decide if processed files should be deleted or not after processing, and to enter a password. The password should be a string, expressing, for example, easy to remember sentence. Entered password is then converted into the random hexadecimal key of selected length. Clicking the button <Info>  causes the presentation of the author of the binary file. The button <Encipher/decipher>  can be now clicked, which will generate the window, allowing to pick the directory with files to encrypt or decrypt:

Fig. 2. Windows for selecting directory containing files to process

Clicking he button <Select directory>  starts the encryption/decryption procedure.  The window from Fig. 2 disappears, and the user will see in the text box of the application window with the result of operation. As can be seen, the selected directory has been encrypted and the name of encrypted file is a concatenation of original file name and the extension  cript. This way the program recognizes which operation should be done. It should also be noted that if the directory contains both encrypted and non-encrypted files, the application does not work.  The processed directory must not contain subdirectories.

Fig. 3. Application window after performing directory encryption

To decrypt, the application should be opened, the same data ought to be entered and the directory as in Fig. 2 must be selected. It is evident that the password must be exactly the same as for encryption.

Fig. 4. Application window after performing directory decryption

The above example concerned hard disk directories encryption/decryption. The encryption/decryption of the same files placed on flash disks is much more slower (see Fig. 5)

Fig. 5. Encrypting/decrypting the same files located in the flash disk

Legal Notice: This application may contain errors and Maplesoft is not liable for any damages resulting from the use of this material. This application is intended for non-commercial, non-profit use only. Contact Maplesoft for permission if you wish to use this application in for-profit activities.