I\'m using gradle (assembleRelease) to generate the release apk.
I have saved the keystore file in project/app/filename.keystore (Within the application
I was using double-quotes with alias and passwords as shown below
storePassword="spass" keyAlias="kalias" keyPassword="kpass"
Removing double-quotes solved my problem
storePassword=spass keyAlias=kalias keyPassword=kpass