How to package the soapUI source by secuirty signers

Actually we have a requirement on SoapUI for multipart message. Hence, we have modified the source files and override the files in the SoapUI Jar which is located in SoapUI installation/bin directory. But while running the SoapUI, it's throwing some security exception. I thought the class files are encrypted by SHA1 algorithm, whatever the class files in the SoapUI jar (Jar file in the installation directory).

How do we deploy the modified class into existing jar file, which should be supported by security (SHA1 supported) after made a jar?

How do we package SoapUI Source files after modified the source (How it's working the soap.executabe file after installed)?

Please let us know, if you have any answers.

Thanks,