Contents of the EPW.DOC file
EPW -- "EXECUTABLE FILE PASSWORD"
Password Encryption Utility for Executable Files
Version 1.2 - Copyright (C) 1987 by Alan D. Jones
This "shareware" is provided on a non-commercial basis for
individual usage only. Should you find EPW useful please
contribute $15 to the author at the following address:
8823 Wind Stream
Houston, Texas 77040
Source code is available for $40. This also places you on the
mailing list and you will receive all future updates to this
program (including new source code) whenever such updates occur.
I am open to suggestions for improvements or changes to this
program. Write me at the above address, or CompuServe 74030,554.
EPW is a password-security utility which modifies an executable
file (.EXE or .COM) in the following way:
1. A password is requested which is then convoluted to form a
starting encrypt/decrypt key.
2. The names file is loaded into memory and encrypted.
3. Non-encrypted code is added so that it will execute first.
4. This combination is written to disk, overwriting the
The result of this is as follows:
Any file which has been processed by EPW, when executed, first
places the prompt "Enter password:" on the screen. The user must
then enter the exact password used in the encryption process.
The encrypted portion of the file (corresponding to the original
file) is then decrypted using the entered password, arranged in
memory just as if a "clean" copy of it had been loaded, and
The syntax of EPW is:
EPW [/A|/R] filename
/A and /R: "Add password" or "Remove password". These two
are mutually exclusive.
filename: The executable file to be processed.
EPW works on both COM and EXE files. The resulting protected
file will have the same loader type and extension. Different
procedures are used for the two types, but usage is identical
from the user standpoint.
EPW now supports "incorrect password" warnings. This is
accomplished by the use of a 4-byte CRC inserted near the
beginning of the encrypted file. The CRC does not contain enough
information to allow a "safecracker" to be written for this
program, but for the same reason it does not absolutely guarantee
that there is not some incorrect password which will be
erroneously accepted as "correct". The probability of this
occurring in any given instance is 1/4,294,967,296, which should
be low enough for most purposes.
And a final note: Upper and lower case letters ARE
distinguishable by EPW. Remember your exact password.