FREEWARE PROGRAMS FOR WINDOWS & DOS by MD@X2TEK

                  X2SECDAT RANDOM NUMBER  FILE
                         ENCRYPTION INFORMATION
by Maurice Dyke
       Powerbasics and their Turbobasic predecessor are the only compilers I have found which seem to be suitable to use for file encrypting with pseudo-random numbers by my method because with them the same seed number always creates the same random number sequence which some other Basics do not seem to do.  My general file encryption procedure is summarized in the next paragraph.  I do not know how secure it is but I think it is good enough for my files on a non internet connected PC even though the random number generators used may not be secure cryptographically since multiple PRNG sequences are used for each file character processed. 
       First, the selected password PW, root filename RFN, and file size are used to generate pseudo-random numbers which are used to transform PW to PW2 and RFN to RFN2.  Next,  each file character is transformed to a new one and then encrypted by an XOR with a PW2 encryption key which is modified after each usage with a random number which depends on RFN2, file character position, and file size.  The encrypted characters are collected into groups of 8 to form 64 bit quad-words which are then subjected to a bit rotation by the value of another random number prior to storage in the PW secured encrypted file so that each character in this file does not correspond to a character in the same position in the original file .

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