pb with signed jar in global jar

[a.too]

Hello,

I work with eclipse and i use ant to compile en jar my project, i have
a problem with
somes signed jars (I don't have the sources of these jars) if I
execute the compiled project in eclipse environnement the result is
ok, but when I want to execute and external jar including these signed
jar I find the
Following error :
Exception in thread "main" java.lang.SecurityException: no manifiest
section for signature file entry ...
Have you an idea to specify in ant the good script to build a jar
without this error
Thank in advance for your answer