Access restriction: The type 'RSACipher' is not API

解决方法：

http://*.com/questions/860187/access-restriction-on-class-due-to-restriction-on-required-library-rt-jar

1. Go to the Build Path settings in the project properties.
2. Remove the JRE System Library
3. Add it back; Select "Add Library" and select the JRE System Library. The default worked for me.

This works because you have multiple classes in different jar files. Removing and re-adding the JRE lib will make the right classes be first. If you want a fundamental solution make sure you exclude the jar files with the same classes.