Hi,

Lately we have had some problems with the file caching and "checksum 
error". It seems to be related with http proxy servers and/or file caching.

When a new version of the applet is deployed (new is called v2, old is 
called v1), the v2 bootstrap loader knows how to cache and download plugins.

Bootstrap loader also knows the checksum of the plugins, which is used 
to verify the integrity of the applet and plugins. If a system has been 
using v1 and applets are upgraded to v2, some file caching servers/proxy 
servers caches the v1 files when the v2 bootstrap loader tries to load 
v2 plugins. This results in a "checksum error" during initialization of 
the applet.

Another side effect that we have observed. As the openoces applets 
becomes more and more widespread and implemented in various systems and 
not always running with the latest version, e.g. Danish SKAT might be 
using 1.6.4 applet, others like ATP might use an older version. If the 
user switches between the systems, SKAT, ATP and others, the plugins 
which is cached locally and maybe even on http proxy servers, will 
overwrite each others plugins. This will break the caching principle and 
the end user feel is that the applets and plugins is downloaded (almost) 
every time the user logs on or signs documents using OpenOces applets.

Its also known that caching servers sometimes chooses to ignore the 
various "expires" and "no-cache" pragmas in the HTTP response. And 
flushing the cache/proxy servers is not always in the control of the end 
user.

This can be solved with a version naming principle. Bootstrap loader 
applet and plugins can have version specific names; e.i. 
bootstrap-1.6.4.jar, pkcs12-1.6.4.zip, pkc12-1.8.0 etc. The file cache 
and end user caching will then cache the used versions, with no 
overwriting of cached files.

Best regards,
Bo Friis
(former member of the OCES core development team)

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