When I tried to use’s APK re-signer, I encountered problems with the on PC and MAC with the JAVA_HOME and ANDROID_HOME variables not being set. Via StackOverflow and general poking around, I eventually got the re-signer to work:

Mac (10.8.3)

add the following to your .bash_profile
export JAVA_HOME=$(/usr/libexec/java_home)
export ANDROID_HOME=/Users/myname/Development/sdk


In System Properties > Advanced > Environment Variables set two system variables (depending on your install locations);
JAVA_HOME C:\Program Files\Java\jdk1.6.0_24\

Note: in the case of the re-signer tool, if double clicking on the jar doesn’t work (you are still asked to set the JAVA_HOME variable), try running from your command line; java -jar re-signer.jar.