What is Yull?

Yull is a desktop file encryption application which runs on Windows. It has two flavors: the command shell version, yull.exe, and the GUI version, yullg.exe.

How do I try it out?

Go to the Downloads page and click on the link for the latest version of Yull.

This will download the Yull compressed file (ending in .zip) to your default downloads folder.
Depending on what is installed on your system, you can double-click the file and unzip it using either Zip, 7-Zip or RAR or other applications.
You can copy Yull.exe and YullG.exe to any location you want.

See the Guide for more information on how to set up Yull.

No Installation

After you unzip Yull.exe and YullG.exe, you need only copy them to wherever you want. If you decide Yull is not for you, you can just delete them. There is NO INSTALLATION with Yull and NO CONNECTION TO THE INTERNET. So whether you download Yull from this web site or just copy it from a friend, it's all the same.

Of course you should always validate your zip file and Yull using FCIV. See the Note on the Downloads page.

Features of Yull

A Quick Overview of Yull's Features

Use Any File as a Key

Most (or all) other encryption programs use a small file as a Key. As far as I know, this file is composed of random (or semi-random) values. For AES, the U.S. Government-blessed encryption standard, the key size is either 16, 24 or 32 bytes long. For Yull the key can be any file and is restricted only to the file size being between 100 and 50,000 bytes. You can use text files; files of all one value, system files like DLLs. With Yull it doesn't matter.

The Key Is Not The Key

The name of your key does not have to be stored anywhere. Yull can ask you for it at runtime. But even if the key is stolen, it is useless without all of your options. Those options can be stored in an encrypted options file but critical ones do not have to be stored anywhere. Yull will ask you for them at runtime. Yull encrypts your key before using it, using a SHA512 hash.

Shred Original Files

Set the Shred Option and as soon as your files are encrypted they are shredded. The files are overwritten many times by much larger, random data. Then they are truncated; then they are deleted.

Note: While this method will delete files, it is not 100% secure since it relies on the file system and does not directly interact with the hardware. There are various file shredding applications available. See DigitalCitizen File Shredder Reviews and PCSupport Reviews for more information about this. There are many detailed discussions concerning issues of securely deleting files, including data held in the shadow copy.

For ordinary uses, the Shred option is great, but it is not secure. It is not clear if any shred procedure apart from physical destructions of the disk is totally secure.

Many Options - But Easy to Use

Once the options are set up (which is easy to do), encryption and decryption is just two clicks away

Your options file can be encrypted and that key is never stored.

Encrypt Entire Folders With Two Clicks

Encrypt files using wildcards or simply folder names.

Many Levels of Encryption

Yull has six encryption levels. At the Max level some files can go through billions of encryptions. At the Plank (lowest) level, files go through 100,000s to over a million encryptions, of course this depends on the file size and the options. For instance, at the lowest (Plank) level, a 4 byte file on my system will undergo about 110 encryptions, a 128-byte file 2869 encryptions, and a 12288 byte file 1,073,949 encryptions. This is with the default, "out of the box," settings. You can change these with ease. At the NORMAL (middle) level, 4 byte file gets 4770 encrypts, 128 byte file gets 163578, and the 12288 byte file 10,170,081 encrypts.

No one but you knows how deeply encrypted your files are. A plank-encrypted file looks like a max-encrypted file.

Plank is very fast; Max slow. But if your data is extremely critical, Max is the way to go.

Yull Runs From Anywhere

It runs from your hard drive; from a USB drive or an external drive or flash drive.

Speaking of Speed

Yull does a LOT of work. It works at about one million encrypts per second. That's plenty fast for most people but for some where time is critical, you might want to lower some of the options, the rounds, say to between 1 and 10, and the read buffer size as low as possible. Both of these are critical regarding the number of encrypts because some of Yull's encryption routines call others, which can call others, etc. On the other end, MAX can be VERY SLOW. But then again, it's much faster than taking a few years' remedial action when your data is stolen. And, there is nothing in the output file to indicate how many enrypts it has gone through.

Yull's Options Control Everything

Yull's option file is a text file. You can name it whatever you want. You can encrypt it. You can have comment lines or other text in it. Yull ignores it all except valid options.

Yull Can be Run as a Job or from a Batch File

You get two versions of Yull: Yull.exe and YullG.exe. Files encrypted with one can be decrypted with the other, and visa versa.

Yull.exe is a Console app. It runs in PowerShell or a DOS Console command shell.

No Installation

Yull does not require installation. You can copy the Yull executables anywhere you want. Yull makes NO CONNECTION TO THE INTERNET.

Yull does not modify your computer in any way.

Yull's Routines Are Not Government Approved

This can be a good or bad thing, depending on your view of the Government. Yull's encryption routines were written by me from the ground up using principles (I believe) no one else uses. That too is good or bad, depending on your views of encryption.

I welcome the scrutiny of academic cryptographers or anyone who knows this field.

See the The White Paper for a detailed discussion of how Yull works.