Android How to - Verify data integrity using sha2








Question

We would like to know how to verify data integrity using sha2.

Answer

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/*from  w ww .  j av a  2s  . com*/
class AeSimpleSHA {

    private static String convertToHex(final byte[] data) {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < data.length; i++) {
            int halfbyte = (data[i] >>> 4) & 0x0F;
            int two_halfs = 0;
            do {
                if ((0 <= halfbyte) && (halfbyte <= 9)) {
                    buf.append((char) ('0' + halfbyte));
                } else {
                    buf.append((char) ('a' + (halfbyte - 10)));
                }
                halfbyte = data[i] & 0x0F;
            } while (two_halfs++ < 1);
        }
        return buf.toString();
    }

    public static String SHA1(final String text) throws NoSuchAlgorithmException, UnsupportedEncodingException {
        MessageDigest md;
        md = MessageDigest.getInstance("SHA-1");
        byte[] sha1hash = new byte[40];
        md.update(text.getBytes("iso-8859-1"), 0, text.length());
        sha1hash = md.digest();
        return convertToHex(sha1hash);
    }
}