Android/Java Verify Large File

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http://stackoverflow.com – I currently have a process in an Android app that checks a few ZIP files against a signature file using a signed certificate much like what is demoed here (http://docs.oracle.com/javase/tutorial/security/apisign/vstep4.html) However, since my files are all 200MB - 900MB it takes anywhere from 11-25 minutes to go through all the files and verify. We are currently using "SHA1withRSA" and are wanting to upgrade to use "SHA256withRSA". But, that takes even longer since it is a more enhanced encryption. The iOS counterpart to this app does the verification of the same ZIP files in around 2 minute (HowTos)