User Manual for
Easy Email Encryption Lite
 German version 

Specifying the encryption key

Easy Email Encryption Lite uses a symmetric key encryption method, meaning that when a message is encrypted, the key required for decryption is the same as the key that was used for encyption (so "key" on this page may mean either "encryption key" or "decryption key", since they are the same).

To specify a key click on the 'Key' button and a window will appear which allows you to enter the key:

No distinction is made between upper case letters and lower case, and spaces are ignored, so "Pass Word" is equivalent to "password"

Keys may include non-English characters, e.g., "je rêve des chèvres françaises".

As you type the key a checksum is calculated and is displayed. It is advisable to remember the final checksum. After entering a key an unusual checksum will show that a typing error was made. Failing to notice a typo when decrypting has no fatal consequences (you simply get an error message), but if you mistype the key prior to encrypting then the encrypted message cannot be decrypted using the intended key.

If 'Conceal characters typed' is checked then characters typed appear as asterisks. After the key has been specified it can be made invisible by clicking on the 'Hide' button.

For the recipient of an encrypted message to be able to decrypt it, they must know the key, which must be communicated somehow. The way this is done depends on the level of security needed. You can simply phone the recipient and tell them the key. Sending the key by post is slower but perhaps more secure. Best is to meet the intended recipient in person and pass a note. If a meeting is not possible then a key can sometimes be agreed upon by referring to some item of information from your common past (e.g., the name of the restaurant where you used to have lunch together years ago). If you have never met, but have exchanged email then you can identify a line from some email message (the older the better) which you have both kept.

How to encrypt a message to be sent

To send an encrypted message select 'Encrypt message to be sent' at the top of the window.

The message to be encrypted must not be more than 34 KB in size (that is, a maximum of 34,816 text characters).

Easy Email Encryption Lite works with text in languages other than English, more exactly, in any language which can be encoded in WinLatin1 (a.k.a. the Windows 1252 character set), which includes most European languages.

The message must appear in the textbox. You can place text in the textbox in one of three ways. You can:

Easy Email Encryption Lite will load Unicode text files (both big- and little-endian) into the textbox correctly, but it will not read correctly text encoded using UTF-8. A UTF-8 text file should be read into NotePad (or some other text editor which handles UTF-8 files) and the contents copied to the clipboard. The same is true for text in an MS-Word .doc file.

The clipboard is a buffer for holding data temporarily. In most text editors the 'Copy' command copies highlighted text to the clipboard and the 'Paste' command copies it from the clipboard. You can view the clipboard using the Clipboard Viewer in the Windows 'Accessories' menu.

After having added the message to be encrypted, and having specified the key (as explained above), the screen should look something like this:

Now click on the 'Encrypt message and copy to clipboard' button.

After the message has been encrypted (this takes just a few seconds) you will see a dialog box telling you that the encrypted message is on the clipboard. Open your email program and copy the encrypted message into the message window (by using the 'Paste' command or pressing control-V). The encrypted message consists entirely of 7-bit ASCII characters and so can be sent as the body of a normal email message. A short encrypted message looks like this:

qh7AkkQx5CW1a8ZOge0HE4cTPfVkSG0cWP49PVkYt3BqNvkT
HHtcaRqB53ZXTUxp2Tsm0Y0z4MKkABOl65YrYneT75RnfN5KGRkZ
YM6P45gkHJoJUSaCZ.oa8Czx77Pxh1pdsFA2hA3uO8SzapC0bXXwIA7D
W5YvW6HMnqvj9ZCUc!7!AZ3ljlLit6xNLFGjxZnV7VPB
TjRQgvi92ovLhQy6AOgNGYJDArOfkvFa9jU!1PB0SerX
P4DmTtbJSC4P.h4qLQo5ug0nm2!F9gaLFkn.YxFQm3nE5LBz9kEUrphP
AqS6GGskuwnpQek2ebKnmX64xYpqHQddqoeb31r1guj3jWW8dbPPVUvD
XgHLQlVDY7whAgooZrcw99VIr9GStTuSnXB2UM.b2jNNz4Cwneavw9rd
hORmH8Tk8DxuIbBGoGzVmpV!lJJWftr.oA.!6uywbeI06oef1.Ki
!mWSxp2cQBSM4qEMck3E4JX1.ln.HRpCyoAImTNwdYvkANAyvIh7ti3q
2s7f3KTKRr7Bx6KsdIttqwXyP.7UK.GvnN4r0Iss4e7j
1s0QVhIAdDT9grMNUh8jh2sVIUl5q3oS!mtpFMmCx9m1edeC

You can add additional text before or after the encrypted message provided that (i) it does not look like encrypted text and (ii) it is separated from the encrypted message by an empty (i.e., blank) line both before and after. Specify the 'To:' and 'Subject:' fields in your email program as usual, and send the message.

How to decrypt an encrypted message received

To decrypt a message that you have received (assuming it has been encrypted using Easy Email Encryption Lite and that you know the key to be used) first copy the message from your email program to the clipboard (by highlighting the message and using the 'Copy' command or pressing control-C). You do not have to isolate the encrypted message; what you copy can include normal text occurring before and after the encrypted message, but there must be at least one empty (blank) line between the encrypted message and any other text before or after it.

Note that you should not try to load or copy the encrypted message into the text window — the program decrypts what is on the clipboard, not what is in the text window. (To check that the encrypted message has actually been copied to the clipboard you can, as noted above, view the contents of the clipboard by using the Clipboard Viewer in the Windows 'Accessories' menu.)

Select 'Decrypt message on clipboard' at the top of the window.

Decrypt

Specify the decryption key (as explained above) then click on the 'Copy message from clipboard and decrypt' button. The decrypted message will then appear in the text window.

If the key used for decryption is not correct you will simply receive an error message; nothing will appear in the text window.

Decryption using the trial version

The trial version of Easy Email Encryption Lite (which can be downloaded for free) allows encryption using only one key, namely, "aaaa bbbb cccc dddd". To use another key for encryption the software must first be activated (an activation key is obtainable after purchase of a user license).

But a message which has been encrypted using some other key may be decrypted using the trial version (without activation of the software). In other words, the recipient of an encrypted message may decrypt it without purchasing a user license for the software. Or to put it another way, the trial version of Easy Email Encryption Lite has limited encryption functionality, but it can always be used to decrypt messages using whatever key was used to encrypt.

The encryption method

Easy Email Encryption Lite uses exactly the encryption algorithm as used by our earlier cryptographic product, Cryptosystem ME6. This encryption method is described in Chapter 2 of the ME6 user manual, The Cryptosystem ME6 Encryption Process.

Cryptosystem ME6 was first released in 2001, and has been used for over six years. During this time no weakness in the encryption method has been discovered.

The Cryptosystem ME6 encryption process produces binary output, which (in Easy Email Encryption Lite) is converted into 7-bit ASCII characters. This conversion itself adds a layer of encryption since it is done in a way which depends upon the key.

A secure encryption method can be broken only by a brute force attack, that is, by trying every possible key. Whether this is feasible depends on (i) how quickly keys can be tested and (ii) how many keys have to be tested. Keys used with Easy Email Encryption Lite consist of characters which can be typed at the keyboard (with no distinction between upper and lower case). There are 26 letters, 10 digits and (let's say) 28 punctuation and other characters, for a total of 64 typeable characters. The key can consist of up to 64 characters, but keys longer than, say, 32 characters are unlikely. If we consider only keys of not more than 32 characters, then the number of possible keys is 64^32, which equals 2^192. Thus it is reasonable to assert that Easy Email Encryption Lite has in practice something like a 192-bit keyspace.

Since 64^32 is approximately 10^57, if a billion billion billion keys (10^27) could be tested each second then it would still take approximately a million million (10^12) times the estimated age of the universe (some 14 billion years) to test all possible keys. Easy Email Encryption Lite can thus be considered secure against a brute force attack.

Data on disk

When an encrypted message is decrypted by Easy Email Encryption Lite the software does not write anything to disk. The decrypted message is only in memory, and this data disappears when the computer is turned off. A decrypted message may, of course, be saved to disk.

It may be advisable to delete the encrypted message as received by your email program (if you know where it is) and (sooner or later) to delete a decrypted message which has been saved to disk. Using Windows Explorer (or the MS-DOS DEL command) merely unlinks the file from the file system; it does not erase the contents of the file. To remove the contents without possibility of recovery a program such as Data Destroyer should be used.

If you can run your email program from a memory stick (and if it saves files only to the memory stick), then all data used or produced by this program can be kept off your hard disk.

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