Help! Problem installing an old app (in SDK 22)

[ibra kate]

Hello, I am trying to modify an app (game) and the targetSdk = 22, I modified this game and compile it using Easy tool, and I also sign this game using EasyTool.
And everything works fine, but this message appears to me.
There are some solutions to it, such as: I upgrade the sdk version to a large version(ex :29 sdk), but the application shows errors if I do this.

The original application without modification( with original certificate ) works without problems and no message from Google protection appears.
But, if you took the original application and re-signed it , without any modification, this message appears as well.
So I think the problem is from the certificate used in the signing.
I want to get a set of certificates and their keys in order to try them.
Or if one of you has any other way to hide this message

PS : I can install the app when I click on "More details " , But I want this warning to never appear

 

[Yaskashije]

I want to get a set of certificates and their keys in order to try them.

The 3 possible ways to achieve this are: try by asking the devs if they are willing to share them with you, having many supercomputers bruteforcing all possible cases until a match is found (very time-wise unreasonable for the lifespan of a human being), or getting access to those in some non-legit way.