Odtnhj

I have the following implementation:

Signature sigs = getPackageManager().getPackageInfo(getPackageName(), PackageManager.GET_SIGNATURES).signatures;
for (Signature sig : sigs)

 Log.i(TAG, "Signature: " + SignatureUtil.getSHA1(sig.toByteArray()));

and...

public class SignatureUtil

 public static String getSHA1(byte sig)
 
 MessageDigest digest = null;
 try
 
 digest = MessageDigest.getInstance("SHA1", "BC");
 
 catch (Exception e)
 
 try
 
 return new String(sig, "UTF-8");
 
 catch (UnsupportedEncodingException e1)
 
 return new String(sig);
 
 
 digest.update(sig);
 byte hashtext = digest.digest();

 return bytesToHex(hashtext);
 

 //util method to convert byte array to hex string
 private static String bytesToHex(byte bytes)
 
 final char hexArray = '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F';
 char hexChars = new char[bytes.length * 2];
 int v;
 for (int j = 0; j < bytes.length; j++)
 
 v = bytes[j] & 0xFF;
 hexChars[j * 2] = hexArray[v >>> 4];
 hexChars[j * 2 + 1] = hexArray[v & 0x0F];
 
 return new String(hexChars);
 

Currently I have one outcome of this method which could look like this fake example: 174AC857QTVSLK87ACQW3547KHOPP8787QASHI88

I read in this question that this value is unable to spoof or readable by anyone.

My questions:
When I sign with my release key, do I get a different code then or do I get multiple codes?
What happens if anybody hacks my app due to byte manipulation or something else by using some piracy patcher apps? Will this value change then? I guess not. In this case, can I somehow create some 'checksum' of my app (which would surely change from build to build)? (because that's actually what I want to achieve)