Encryptor is a shareware program. This means that you are invited to try it out and play with it, and you are encouraged to give away copies of it. If you decide you want to make any serious use of Encryptor, however, you are asked to send the (miniscule) fee of $5.00 to me at the address below. When you do so, please mention the name of the program and version number shown above.
Karl Bunker
321 S. Huntington Ave.
Boston, MA 02130
Encryptor allows you to encrypt (scramble) and decrypt (unscramble) all types of ProDOS files. A four-character password, which you make up, acts as the key to an encrypted file. You enter this password when using Encryptor to encrypt a file, and enter it again when decrypting. No other password will successfully decrypt the file. No normal method of examining the data in the encrypted file will give any usable information about the original file's contents. Without the correct password, the encrypted file is effectively "locked"; both unusable and indecipherable. Encryptor can create two types of encrypted files: regular encrypted files, which are decrypted by re-processing them through Encryptor, and "self-decrypting" files, which require a password, but not Encryptor itself to be decrypted. Encryptor also has a "purge" function, which allows you to completely erase a file and its data from a disk. These various options are described in detail below.
Using Encryptor
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The use of Encryptor is fairly obvious and self-evident. When you select anything other than "Quit" from the main menu, you are sent to a disk catalog screen, so that you can select the file you want to process. At the first prompt, you enter the prefix you want to catalog, or accept the one shown by pressing <return>. When the catalog is displayed, you select the file to be processed by moving the inverse bar, and press <return> to begin the function you selected. If you press <return> when the inverse bar is on a directory file, then this directory will be added to the prefix, opened, and cataloged. Pressing <esc> at any point in Encryptor will back you up to the previous stage in the program.
Encrypting a file:
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After you select a file from the catalog, Encryptor will prompt you for a name to use for the new encrypted file that it will create. A default pathname, the source file's name with the suffix ".ENC", is offered. You can accept this name by pressing <return>, or enter another. The object file will not replace your source file, but will be an entirely new file. Your source file will not be affected by the encryption process. The Encrypted file will be the same size as your source file, plus four bytes. If the filename you enter is the name of an already existing file, Encryptor will ask you if it's okay to delete this file. Finally Encryptor prompts you for the Encryption Code, or password. This can be any four alphabetic, numeric, or punctuation characters; for example: "CODE", or "BOP!", or "5&10". Encryptor will then create the new, encrypted file; this takes a few seconds. The source file and object (encrypted) file can be on different disks in the same drive; Encryptor will prompt you to swap disks when necessary.
Decrypting a file:
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To decrypt a file, the procedure is the same. Encrypted files are shown in Encryptor's catalog as type "ENC". Select the one you want to decrypt, and when prompted, enter a name for the decrypted file (or accept the default). As when encrypting, you will lastly be prompted for the password. If you enter the correct one, the new object file which is produced should be identical in every respect to the original, un-encrypted file. If you enter an incorrect password, Encryptor will let you know.
Making a self-decrypting file:
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Self-decrypting files will be useful for situations where a file is going to be freely distributed, but you want to limit the number of people who will actually be able to USE that file. For example: The author of a shareware program could distribute copies of his/her program, including with it a small documentation file which gives enough information about the program for users to try it out. Also included would be an encrypted copy of the complete documentation file. Then, when a user sends the author the shareware fee, the author would send the user a password which decrypts the complete documentation file. This password could be sent via e-mail, phone, or regular mail; this would be less expensive and faster than mailing a disk with the full documentation file. Alternatively, some other kind of "bonus" for paying users could be included in the form of an encrypted file. The advantage of self-decrypting files in a situation like this is that Encryptor itself, and instructions for its use, don't have to be included along with the other files.
A self-decrypting file is created with Encryptor much like a regular encrypted file. However, a self-decrypting file is a binary-type file which can be BRUN from BASIC.SYSTEM. When it is BRUN, it prompts the user for its password. If the correct password is entered, this file uses data contained within itself to create a new file - a replica of the source file that was processed into the self-decrypting file. Thus, a self-decrypting file is "stand-alone"; it doesn't require Encryptor, and a couple of sentences are sufficient to explain its use. One limitation on self-decrypting files is that it must not be so large that it can't fit into available memory when BLOADed at $2000; the maximum size for the source file is 56 blocks.
When using Encryptor to make a self-decrypting file, you are - as with "regular" encrypting - prompted for a name to use for the new self-decrypting (S-D) object file. Additionally, you are prompted for a name for the S-D file to use when it decrypts itself. This will be the name of the new file that the S-D file writes to the end user's disk. If you like, this can be the same name as the name of the S-D file. If this is done, the decrypted version of the S-D file will replace the S-D file itself on the disk. Self-decrypting files check the correctness of the entered password before deleting anything, so they won't erase themselves unless the password is the right one. It is strongly recommended that you use a filename alone for the name of the decrypted file, rather than a full /VOLUME/FILE pathname. You usually can't be sure what volume will be on-line when the self-decrypting file is BRUN. It is also up to you to ensure that you use correct ProDOS syntax when you enter the name. If you don't, the S-D file will halt with a BASIC.SYSTEM "SYNTAX ERROR" after the password is entered. The name of the decrypted file that will be created is displayed on-screen by the S-D file when it is BRUN.
As a demonstration of this self-decrypting shareware "scam", I'm including with Encryptor a self-decrypting version of a completely silly little BASIC game which I wrote about a zillion years ago. This file is called WHATSIT. Send me the shareware fee for Encryptor, and I'll send you the password. Give me a Compuserve or GEnie e-mail address if you have one, or I'll just jot the password onto your check when I cash it.
Purging a file:
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Normally, when you "delete" a file from a ProDOS disk, the file's name is removed from the disk catalog display and the disk space used by the file is released for use by new files. However, until the the disk sectors that the file occupied are overwritten by new files, the data contained in the deleted file is still on the disk. For this reason, various ProDOS disk utilities can sometimes either "undelete" a file, or read a deleted file's data directly from the disk. In some situations, this can be a problem. With highly sensitive data (or extreme cases of paranoia), you might want the option of truly erasing a file from a disk, without any possibility of its contents ever being viewed or used by anyone. You might want to do this with the original copy of a file that has been encrypted, for example. (Keeping in mind some warnings given below.) Encryptor's "Purge" function gives you this option. To use this function, simply select a file from the catalog as with the other Encryptor functions. Encryptor will give you one last chance to change your mind before purging the file.
How good is Encryptor?
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No code is unbreakable, and no method of data encryption is uncrackable. A file encrypted with this program CAN be deciphered without prior knowledge of the password. However, I believe I have been successful in seeing to it that doing this would require an unreasonable amount of work and time. The CIA (or KGB) would not be too impressed with the security provided by Encryptor. For less serious purposes, it should be more than adequate. It is important to keep in mind one consequence of Encryptor's effectiveness: If you should use this program to encrypt a file, and then delete the original of that file, and then forget your Encryption Code - you're on your own. I (the author of Encryptor) can't help you; your file is GONE. Period. Excuse me for yelling, but: DO NOT ERASE YOUR ORIGINAL FILE UNLESS YOU ARE WILLING TO TAKE THE RISK OF LOSING IT!
