When making web applications you sometimes need to pass data along with the form which isn't visible to the user. Database IDs are the most common, but texts and IDs are sometimes necessary too. For this reason there is a
<hidden> field in HTML, but it has a drawback - any hacker with a basic understanding of what he is doing can modify the value. It would be better if such values would be tamper-protected, if not outright encrypted.
I need to pass a value through hostile territory. The value is most often an integer (and that most often less than 65'000, so mostly just two non-zero bytes, rarely three, almost never 4). However sometimes the value can also be a string (short, a few hundred characters at most). I'm OK with using different algorithms for different kinds of data.
I want to tamper-protect the value, so that it cannot be changed en-route without detecting. Hiding the data isn't necessary, but doing so would be a bonus. So either tamper-protection or encryption would work.
Whatever the algorithm, I want to have the output as short as possible without sacrificing too much of security. This is because it's a webpage and shorter data means faster response times. Also, the HTML code becomes easier to read if there aren't lengthy random strings in it.
What algorithms would you suggest for this purpose?