Modified Version of WhatCrypt Key Extractor from https://github.com/EliteAndroidApps/WhatsApp-Key-DB-Extractor
Remember: This version will not be working for Android 7.1.1 with WhatsApp 2.17.427 otherwise you will get the error message:
Installing legacy WhatsApp 2.11.431... adb: failed to install tmp/LegacyWhatsApp.apk: Failure [INSTALL_FAILED_VERSION_DOWNGRADE] ... FAILED! ErrorCode: 1