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 Encrypted files using Cygwin and OpenSSL

Daniel Petri


Using Cygwin, the free open-source terminal emulator, in coordination with OpenSSL, you can create cross-platform encrypted files. The files created using Cygwin can be exported using mobile media including thumb drives, CDs, external hard drives, etc. Cygwin and OpenSSL are bundled in the download of Cygwin. The following tutorial (although demonstrated using Windows Vista) can be applied to Windows XP, Linux, and Mac OS.

Download Cygwin from the project homepage. Cygwin is the executable located approximately half-way down the page.

Double-click setup.exe to begin the installation and click Next.

Choose Install from Internet and click Next.

Leave the installation directory as C:’cygwin and leave the Default Text File Type set as Unix/binary and click Next.

Change the local package directory path to C:’Users’USERNAME’ and click Next.

On the Select Your Internet Connection dialog, select Direct Connection and click Next.

Select a mirror and click Next.

Untie the “Net” tab, double-click openssl and click Next.

It will take a few minutes for Cygwin to install.

Leave the default icon selections and click Finish.

Congratulations, the installation of Cygwin is complete. Double-click the icon on your desktop to launch Cygwin.

Cygwin will create several personalization files and will launch the default window (shown below).

In order to create an encrypted version of a file enter the following command:

​openssl des3 -salt -in UnencryptedFile.html -out EncryptedFile.html.des3

Replace “unencryptedFile.html” with the name of a file you would like to encrypt. OpenSSL will prompt you to create a password for the file.

You will now notice an encrypted version of your file was created in the same directory and named “EncryptedFile.html.des3.” If you try to open this file without first entering the password, you will get incoherent output. To decrypt your file, enter the following command:

​openssl des3 -d -salt -in EncryptedFile.html.des3 -out NewUnencryptedFile.html

OpenSSL will once again prompt you to enter your password. Upon successful authentication, OpenSSL will create a new, decrypted version of your file in the same directory.

Once your file is encrypted, you can transport the file onto portable media in the same way that you would transfer any other file. You will be able to decrypt your file on any computer with OpenSSL installed including Linux, Windows Vista or Windows XP, or Mac OS.

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