Password 64 allows you to protect any Basic file that you have labored long and hard to complete. Once the Basic program is modified using Password 64, it can be used without the need for special programs or utilities.
To use Password 64, you must observe two restrictions. First, the file that you wish to protect can not start with a line number of zero (0). For your convenience, a renumbering utility is included. See below for "Renumber 64" information. Second, computer memory beginning at 49152 ($C000) must be free of resident programs, such as RUN's Checksum. If in doubt, load Password 64 from a cold start.
To install Password 64, just load and run it using Menu 64. The operating code is moved to address 49152 (hex $C000) and the loader portion is deleted. Four prompts then appear. Just type in the name of the program that you want to protect. The file must be pure Basic 2.0, with no machine language routines.
Password is not designed to handle Basic look-alikes or binary files. Also, if you are using a disk drive other than 8, list the device number after the filename. For example, enter "MYFILE,9", at the first prompt. Once a device number is entered it becomes the default device for the current session.
The second prompt asks for a password. Specify a password of from one to ten ASCII characters. Use lower or upper case letters, numerals or punctuation. When you press Return three things happen. First, an additional Basic line number 0 is inserted. Then your program is encrypted based on your password. Third, a machine language decode/re-encode routine is appended to the end of the program. Although a machine language monitor easily shows how the decode routine works, without the password, your Basic program is almost impossible to decipher.
The third prompt asks for a filename to save the encrypted program under. As with the original load prompt, you change the default device number by listing it after the filename.
Load and run an encypted program exactly the same as any other Basic program. When the program is run the user is first prompted for the password. The correct password allows the program to run after a short decoding delay. When the program stops running, regardless of the reason, the program's contents are immediately re-encrypted. An incorrect password generates an "access denied" error and the user is returned to Basic.
No other programs or utilities are required. The encrypted program has all the information it needs to run under password protection. If you list the file, all appears is line 0 which is a SYS call to the decode routine. Deleting statement #0 in effect deletes the entire program. You can not edit, list or print a password protected program. You can make copies either by loading and resaving or with a file copier. Keep copies of the unencrypted version for later additions or revisions.
The last prompt asks if you wish to protect another file. Answer yes or no. A disk error or a null response to either of the first three prompts causes the program to exit to Basic. Just enter SYS 49152 to restart.
