Google Play App Signing and Facebook Login

Just to add another option, one can check the device's logcat & there's a Log from Facebook Sdk with the "key" expected/required to login, we can directly copy+paste from there as well instead of converting it through an online tool.

Thank me later

echo YOUR_HEXADECIMAL_KEY | xxd -r -p | openssl base64

Just found out by myself. Actually for Facebook Login, you just need to translate the hexadecimal code of your SHA1 into Base64. You can find some online tools to do it. Hope this helps someone someday =)