Protected shareware

DETAILED DESCRIPTION To satisfy the foregoing goals, in accordance with this invention, the functionality of "protected shareware" is controlled by digitally signed messaging protocol.
Protective code within the shareware controls the functionality of the shareware in response to authorization messages which are supplied directly or indirectly by the shareware supplier.
These messages are digitally signed in whole or part by or on behalf of the shareware supplier using the supplier's secret signing key.
The shareware, in turn, includes the public checking key for this digital signature of the supplier, thereby enabling the protective code to authenticate any such authorization message before acting in reliance upon it.
The shareware includes an integrity self-checking routine which is run at appropriate times to ensure that shareware, including its protective code, is in an anticipated state.
Typically this is equivalent to a finding that the code has not been altered, but it is conceivable that the code might be dynamically altered in some authorized (i.
e.
, "anticipated") way.