How to hash a string in Android?

Question

I am working on an Android app and have a couple strings that I would like to encrypt before sending to a database. I'd like something that's secure, easy to implement, will generate the same thing every time it's passed the same data, and preferably will result in a string that stays a constant length no matter how large the string being passed to it is. Maybe I'm looking for a hash.

Answer 1

This snippet calculate md5 for any given string

public String md5(String s) {     try {         // Create MD5 Hash         MessageDigest digest = java.security.MessageDigest.getInstance("MD5");         digest.update(s.getBytes());         byte messageDigest[] = digest.digest();          // Create Hex String         StringBuffer hexString = new StringBuffer();         for (int i=0; i<messageDigest.length; i++)             hexString.append(Integer.toHexString(0xFF & messageDigest[i]));         return hexString.toString();      } catch (NoSuchAlgorithmException e) {         e.printStackTrace();     }     return ""; } 

Source: http://www.androidsnippets.com/snippets/52/index.html

Hope this is useful for you

Answer 2

That function above from (http://www.androidsnippets.org/snippets/52/index.html) is flawed. If one of the digits in the messageDigest is not a two character hex value (i.e. 0x09), it doesn't work properly because it doesn't pad with a 0. If you search around you'll find that function and complaints about it not working. Here a better one found in the comment section of this page, which I slightly modified:

public static String md5(String s)  {     MessageDigest digest;     try     {         digest = MessageDigest.getInstance("MD5");         digest.update(s.getBytes(Charset.forName("US-ASCII")),0,s.length());         byte[] magnitude = digest.digest();         BigInteger bi = new BigInteger(1, magnitude);         String hash = String.format("%0" + (magnitude.length << 1) + "x", bi);         return hash;     }     catch (NoSuchAlgorithmException e)     {         e.printStackTrace();     }     return ""; }