SignatureUtils.java

package com.ennervoice.user.Utils;

import android.content.Context;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.Signature;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SignatureUtils {
    public static String getOwnSignatureHash(Context ctxt)
            throws NameNotFoundException,
            NoSuchAlgorithmException {
        return (getSignatureHash(ctxt, ctxt.getPackageName()));
    }

    public static String getSignatureHash(Context ctxt, String packageName)
            throws NameNotFoundException,
            NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA1");
        Signature sig =
                ctxt.getPackageManager()
                        .getPackageInfo(packageName, PackageManager.GET_SIGNATURES).signatures[0];

        return (toHexStringWithColons(md.digest(sig.toByteArray())));
    }

    // based on https://stackoverflow.com/a/2197650/115145

    public static String toHexStringWithColons(byte[] bytes) {
        char[] hexArray =
                {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B',
                        'C', 'D', 'E', 'F'};
        char[] hexChars = new char[(bytes.length * 3) - 1];
        int v;

        for (int j = 0; j < bytes.length; j++) {
            v = bytes[j] & 0xFF;
            hexChars[j * 3] = hexArray[v / 16];
            hexChars[j * 3 + 1] = hexArray[v % 16];

            if (j < bytes.length - 1) {
                hexChars[j * 3 + 2] = ':';
            }
        }

        return new String(hexChars);
    }
}