Cryption Overview

Before we get to the specifics on encrypting and decrypting files, let's first look at all the components of the screen and what they signify.  There are two parts - the PassPhrase and File Info section plus the Expansion option.  Be sure to check out the help topics PassPhrases and Depth and Key Management as they contain related information.

The PassPhrase is your key to encrypting and decrypting data.  It can be letters, numbers, anything you can type on your keyboard.  Its length should be 10-20 characters long for best results, but can be smaller.  The Defined PassPhrases dropdown will appear if you have defined PassPhrases and if shown can be used to select the particular PassPhrase you want to use.  You cannot encrypt or decrypt without a PassPhrase.  Under the PassPhrase field is a Keyboard button.  This will allow you to graphically use a virtual keyboard to avoid keystroke detection.

The Depth sets the security level for the encryption or decryption.  A higher Depth yields more security than a lower one.  The range is between 3 and 100,000 and the default is 20.  Bear in mind that with the higher Depth comes the expense of processing time both in generating the keyspace and encrypting/decrypting your file. 

There is also a check box labeled Use Existing Keys which appears whenever a keyspace is present, either by encrypting or decrypting a file, or after performing a Restore Keyspace Files option (Key Management).  This tells Eureka to bypass the normal function of creating a keyspace with the PassPhrase and use the keyspace files present instead.  Eureka creates a keyspace for each different PassPhrase it encounters, so once it has been established, the same PassPhrase will skip the creation of the keyspace since it is already there.  Once the PassPhrase changes, a new keyspace will then be generated.

The File Info section simply defines what file is to encrypted or decrypted, and what file is the encrypted or decrypted data.

At the bottom left is an Expansion option.  What expansion does is add bogus characters between your valid characters to make attacks on the data extremely difficult.  If you wish to use expansion, just click on the Yes option.  You must remember, and if transmitting this file to someone else, they must know to use Expansion when decrypting it.  Try this - create or find a rather small data or text file.  Send it through with NO expansion.  Now look up the encrypted file's filesize.  Now repeat the encryption, this time with Expansion and go look at the filesize again.

NEVER encrypt or decrypt to the same filename.  One mistake (wrong PassPhrase, wrong Depth, used Expansion but didn't remember) and your file is now unrecoverable.  Always encrypt or decrypt to another file so if something goes wrong, you can start over.  If you insist on using the same filename, be sure and have a backup of the original encryption so you can start over.

Encrypting

To encrypt all you have to do is provide the PassPhrase, either by keying it in manually, using the keyboard function to avoid keystoke detection, or selecting it from the Defined PassPhrase dropdown if you have defined them in PassPhrase Management, or, as mentioned above, the keyspace could have been restored and you have checked the Use Existing Keys option.

Next define the File to Encrypt field with the file you want to encrypt and then define the Encrypted File field.  It is popular to use the same filename but change the extension to .enc, or add the extension .enc to the file. 

Now choose whether Expansion is to be performed.  If it is wanted, click Yes otherwise click No.  It always defaults to No.

Finally click on the Encrypt button.  Unless there are errors due to something missing, the keyspace (if new PassPhrase) will be generated and the file encrypted.

Decrypting

To decrypt all you have to do is provide the PassPhrase, either by keying it in manually, using the keyboard function to avoid keystoke detection, or selecting it from the Defined PassPhrase dropdown if you have defined them in PassPhrase Management, or, as mentioned above, the keyspace could have been restored and you have checked the Use Existing Keys option.

Next define the File to Decrypt field with the file that was encrypted and then define the Decrypted File field.  It is popular to use the same filename but change the extension to .dec, or add the extension .dec to the file. 

Now choose whether Expansion is to be performed.  If it is wanted, click Yes otherwise click No.  It always defaults to No.

Finally click on the Decrypt button.  Unless there are errors due to something missing, the keyspace (if new PassPhrase) will be generated and the file decrypted.