src/main/java/org/jivesoftware/smack/util/StringUtils.java
public static byte[] decodeBase64(String data) {
        byte[] bytes;
        try {
            bytes = data.getBytes("UTF-8");
        } catch (java.io.UnsupportedEncodingException uee) {
            bytes = data.getBytes();
        }

        bytes = Base64.decode(bytes, 0, bytes.length, Base64.NO_OPTIONS);
        return bytes;
    }
public static byte[] decodeBase64(String data) {
        byte[] bytes;
        try {
            bytes = data.getBytes("UTF-8");
        } catch (java.io.UnsupportedEncodingException uee) {
            bytes = data.getBytes();
        }

        bytes = Base64.decode(bytes, 0, bytes.length, Base64.NO_OPTIONS);
        return bytes;
    }
Decodes a base64 String. Unlike Base64.decode() this method does not try
to detect and decompress a gzip-compressed input.

@param data
a base64 encoded String to decode.
@return the decoded String.