two of three byte different in sha256 hash function

Question

I am using this function to calculate the SHA 256

public static String getSHA1(String plainText) {
        MessageDigest md;
        try {
            md = MessageDigest.getInstance("SHA-256");

            md.update(plainText.getBytes(Charset.forName("UTF-8")));
            StringBuffer hexString = new StringBuffer();
            byte[] bytes = md.digest();
            for (int i = 0; i < bytes.length; i++) {
                hexString.append(Integer.toHexString(0xFF & bytes[i]));
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

And to be sure of my results, I check this online website http://onlinemd5.com/

the results between my code and the online is almost the same, but you know that it must be equal. for instance

my plain testis:

1234567

the website result

8BB0CF6EB9B17D0F7D22B456F121257DC1254E1F01665370476383EA776DF414

my code result

8bb0cf6eb9b17df7d22b456f121257dc1254e1f1665370476383ea776df414

and this is more examples:

7777777
8C1CDB9CB4DBAC6DBB6EBD118EC8F9523D22E4E4CB8CC9DF5F7E1E499BBA3C10
8c1cdb9cb4dbac6dbb6ebd118ec8f9523d22e4e4cb8cc9df5f7e1e499bba3c10


147258
7A2EC40FF8A1247C532309355F798A779E00ACFF579C63EEC3636FFB2902C1AC
7a2ec4ff8a1247c53239355f798a779e0acff579c63eec3636ffb292c1ac


888888
92925488B28AB12584AC8FCAA8A27A0F497B2C62940C8F4FBC8EF19EBC87C43E
92925488b28ab12584ac8fcaa8a27af497b2c6294c8f4fbc8ef19ebc87c43e

I do know that this is maybe about the encoding. but look i used utf-8 which is what the website used

Answer 1

This is the problem:

hexString.append(Integer.toHexString(0xFF & bytes[i]));

This will lose any leading 0s - in other words, any byte less than 16 will come out as a single hex digit instead of two.

There are plenty of fixes for this. For example:

• Manually append 0 if the value is between 0 and 15 (ick)
• Use String.format("%02x", bytes[i] & 0xff)
• Use a full "byte array to hex conversion" method in a utility library (there are loads around)