Starting from Aug 1994, "NetLib 6.0g" is used to replace "NetLib 5.2" and the encrypt/decrypt method of new library is different from the old library.

When the NEW SB (Verison 5.1e or Ver 5.1ex) is executed, it will try to
determine the UAMST.DBF is encrypted with "NetLib 5.2", then it will perform
the following procedure:-

24.1 COPY UAMAST.DBF UAMAST.OLD
24.2 DECRYPT UAMAST.DBF using "NetLib 5.2" method
24.3 encrypt UAMAST.DBF using "NetLib 6.0g"

The UAMAST.DBF encrypted by "NetLib 6.0g" CANNOT BE READ by OLD SB.EXE but you
can tell users to copy the old UAMAST to replace the new one:
COPY UAMAST.OLD UAMAST.DBF

Then the old SB.EXE can decrypt the UAMAST.DBF

If for unknown reason, the UAMAST.OLD cannot be found, you can tell users to
rename the UAMAST.DBF UAMAST.NEW

The SB (either new one or old one) will generate a new UAMAST.DBF if a UAMAST.DBF cannot not be located.