Continuing with the theme from my last thread where I posted a simple class for encrypting strings using the SHA-512 hashing algorithm, here is an improved version that generates a random 20 byte salt to add in with the string to be hashed. This is then hashed providing greater security.
Due to the random generation of the salt each time a string is hashed, this makes it pretty much impossible to get the same hash for a string, therefore once the salt has been generated the first time round it is stored in sharedPreferences for future uses so that you can use it for checking matches etc
Method of converting the bytes to hex string adapted from maybeWeCouldStealAVan's method @ stackoverflow.
Usage:
Due to the random generation of the salt each time a string is hashed, this makes it pretty much impossible to get the same hash for a string, therefore once the salt has been generated the first time round it is stored in sharedPreferences for future uses so that you can use it for checking matches etc
Method of converting the bytes to hex string adapted from maybeWeCouldStealAVan's method @ stackoverflow.
Code:
public class Crypto {
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
protected static String SHA512(String string, Context context) throws NoSuchAlgorithmException {
MessageDigest md = MessageDigest.getInstance("SHA-512");
String salt = getSalt(context);
md.update(salt.getBytes());
byte[] bytes = md.digest(string.getBytes());
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
private static String getSalt(Context context) throws NoSuchAlgorithmException {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
String salt = preferences.getString("salt", null);
if (salt == null) {
byte[] saltBytes = new byte[20];
SecureRandom.getInstance("SHA1PRNG").nextBytes(saltBytes);
salt = new String(saltBytes);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("salt", salt).commit();
}
return salt;
}
}
Code:
String example = "example";
try {
example = Crypto.SHA512(example, context);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
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