fix transactions bug

http://tools.ietf.org/html/rfc4648#page-7

    The pad character "=" is typically percent-encoded when used in an
    URI [9], but if the data length is known implicitly, this can be
    avoided by skipping the padding; see section 3.2.

http://tools.ietf.org/html/rfc4648#section-3.2

    In some circumstances, the use of padding ("=") in base-encoded data
    is not required or used.  In the general case, when assumptions about
    the size of transported data cannot be made, padding is required to
    yield correct decoded data.