Secure PlayerPrefs in iOS with MD5

Questions & Answers
1

I have locally stored data that will be used for leaderboards and needs to be secure. I am using md5 to save a hash with the data and the hash is validated when the data is loaded.

For example:

PlayerPrefs.SaveInt("score",value);
PlayerPrefs.SaveString("score_hash",Md5Sum(value.ToString()+secret));

then on load, we have:

int value = PlayerPrefs.GetInt("score");
string _hash = PlayerPrefs.GetString("score_hash");
string hash_check = Md5Sum(value.ToString()+secret);
if(!_hash.Equals(hash_check)) {
	Debug.Log("SH: Error, invalid hash "+_hash+" ; "+hash_check);
	return null;
}

My question is, how secure is this method? Can unity apps be decompiled or hacked into where the user will be able to find the secret key?

2

All apps can be decompiled/hacked. The question is really how likely it is that someone will do this, and, if they did, how “bad” that would be. The average gamer is unlikely to try and extract the secret from your code.