I've been working on a program for MS-DOS machines that will encrypt and/or password protect .COM and .EXE files. The way it works is this: It encrypts the entire file specified by the user, then it uses a polymorphic encryptor to encrypt the decryption code for the file and put it in a decryption envelope filled with anti-debugging code. IT then attaches the entire module/decryption code to the file so that it is executed initially when the file is run - at which point it decrypts the file and does whatever relocation is needed (for .EXE files). In the case of a password - it asks for the password, encrypts it and checks it against the stored version, then if they match it decrypts restoration code using the password as a key and continues on. I've got it working really well at this point - but my encryption algorithms are rather simple. I'm fairly new in the encryption biz, and I was wondering what would be good to use for the file encryption algorithm to make it as secure as possible? Of course - the code to decrypt it MUST be present in the file, so if you can bypass the anti- debugging code it's yours, but the polymorphism makes it difficult to do this on more than a case-by-case basis. Still - I'd like to make it to where one can't just run a "decrypt-em-all" analysis program on it and be able to read the included text - but I need a good algorithm for it. Any help/suggestions would REALLY be appreciated. Oh - if you are interested in the protection utilities, email me at the address below - it's freeware. Thanks a lot, Michael Ellison ie63@vaxb.acs.unt.edu If you wish to encrypt any messages E-mailed to me, please use the following key..... -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.3a mQCNAixUuYYAAAEEAKNllAee26qGqxJck3Bftdkrz0MUQLABGMZqVem9UW9kjjS+ rMAafauqYTE5/Kdnx+4Asj0Wgfon0YBtRMT0crMcBYNqVp4//RUh7wrxQNvKFeeO ZGuQp2hyHQqh1FDfWsHG4ldGqIV1YuOXq6oeIDkmbwgf8BRgPcZkwUqsF4b1AAUR tCpNaWNoYWVsIEEuIEVsbGlzb24gPGllNjNAdmF4Yi5hY3MudW50LmVkdT4= =0rss -----END PGP PUBLIC KEY BLOCK-----