Java String to SHA1

Question

UPDATE
You can use Apache Commons Codec (version 1.7+) to do this job for you.

DigestUtils.sha1Hex(stringToConvertToSHexRepresentation)

Thanks to @Jon Onstott for this suggestion.

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Old Answer
Convert your Byte Array to Hex String. Real's How To tells you how.

return byteArrayToHexString(md.digest(convertme))

and (copied from Real's How To)

public static String byteArrayToHexString(byte[] b) {
  String result = "";
  for (int i=0; i < b.length; i++) {
    result +=
          Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
  }
  return result;
}

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BTW, you may get more compact representation using Base64. Apache Commons Codec API 1.4, has this nice utility to take away all the pain. refer here

This is my solution of converting string to sha1. It works well in my Android app:

private static String encryptPassword(String password)
{
    String sha1 = "";
    try
    {
        MessageDigest crypt = MessageDigest.getInstance("SHA-1");
        crypt.reset();
        crypt.update(password.getBytes("UTF-8"));
        sha1 = byteToHex(crypt.digest());
    }
    catch(NoSuchAlgorithmException e)
    {
        e.printStackTrace();
    }
    catch(UnsupportedEncodingException e)
    {
        e.printStackTrace();
    }
    return sha1;
}

private static String byteToHex(final byte[] hash)
{
    Formatter formatter = new Formatter();
    for (byte b : hash)
    {
        formatter.format("%02x", b);
    }
    String result = formatter.toString();
    formatter.close();
    return result;
}

Using Guava Hashing class:

Hashing.sha1().hashString( "password", Charsets.UTF_8 ).toString()

SHA-1 (and all other hashing algorithms) return binary data. That means that (in Java) they produce a byte[]. That byte array does not represent any specific characters, which means you can't simply turn it into a String like you did.

If you need a String, then you have to format that byte[] in a way that can be represented as a String (otherwise, just keep the byte[] around).

Two common ways of representing arbitrary byte[] as printable characters are BASE64 or simple hex-Strings (i.e. representing each byte by two hexadecimal digits). It looks like you're trying to produce a hex-String.

There's also another pitfall: if you want to get the SHA-1 of a Java String, then you need to convert that String to a byte[] first (as the input of SHA-1 is a byte[] as well). If you simply use myString.getBytes() as you showed, then it will use the platform default encoding and as such will be dependent on the environment you run it in (for example it could return different data based on the language/locale setting of your OS).

A better solution is to specify the encoding to use for the String-to-byte[] conversion like this: myString.getBytes("UTF-8"). Choosing UTF-8 (or another encoding that can represent every Unicode character) is the safest choice here.

This is a simple solution that can be used when converting a string to a hex format:

private static String encryptPassword(String password) throws NoSuchAlgorithmException, UnsupportedEncodingException {

    MessageDigest crypt = MessageDigest.getInstance("SHA-1");
    crypt.reset();
    crypt.update(password.getBytes("UTF-8"));

    return new BigInteger(1, crypt.digest()).toString(16);
}

Just use the apache commons codec library. They have a utility class called DigestUtils

No need to get into details.