The ‘here is’ key

Not mentioned in the article is that ENQ is a standard ASCII character (0x05, and previously abbreviated WRU for “Who are you?”) that causes the device on the other end of the line to send back its answerback message.<p>On electromechanical teletypes¹ the answerback message was ‘programmed’ by breaking off tabs from a rotating drum, like an inverse music box.<p>¹ <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Teletype_Model_33" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Teletype_Model_33</a>

It is kinda funny that Apple didn&#x27;t do anything about Caps Lock when they redesigned their keyboard with the touch bar.<p>I cannot imagine professionals or casual users who would need quick access to turning caps lock on and off. When you need caps lock over shift, it is because you are planning to write a lot of all cap text, and so, taking a second to turn it on via the touch bar seems okay. It is prime to be relegated to the touch-bar, while plenty of professionals use ESC all the time while touch-typing.<p>While they were at it, the switch window `command+~` short cut is almost unreachable on non-us like keyboard layouts.<p>If they were gonna break professional users keyboard workflow, why not fix some of the more glaring mistakes in current keyboard layout while they were at it?

It sounds like this was an automatic thing, the host could query the terminal and would get a response without any user input.<p>So that still leaves me with the question of why the key exists?<p>What use cases would you have for voluntarily sending the host your &quot;identification&quot;? Was this used for authentication?

I seem to remember that being used as an attack vector at college: Identify a terminal that was logged on as root (albeit physically inaccessible), then find a way of getting message to it, then send a string that programmed answerback and then triggered it. Usual payload was moving your &#x27;special&#x27; version of a common suid program into place, possibly along with a tweaked version of &#x27;sum&#x27;.<p>This started with &#x27;write&#x27; etc. but became an escalating arms-race.

A colleague had this to say:<p><i>I remember a spate of answerback hacks with vt100s. the remote host could program the message by sending an escape sequence, and then get the vt100 to type the string back. you could make the tty execute commands that would give the attacker privs, and stuff like that. The main fix was hardening mail clients to filter escape sequences; simpler days to be sure, but the basic flaw (non-filtered text) still occurs in html forms</i>

I noticed there are some commonalities between this keyboard and the Japanese layout on PC keyboards.<p>For instance, note the co-location of * and : characters on the same key. It&#x27;s not in the same place on the Japanese layout, but the co-location is the same.<p>Another shared feature between the two is the co-location of the = and - (equals and dash).<p>Next, the tilde in the general same area on the Japanese layout as on this terminal, close to the Return key.<p>Lastly, the correlation between the numeric row keys and their Shift glyphs is almost the same on the Japanse layout and this terminal!<p><pre><code> 1 2 3 4 5 6 7 8 9 0 JPN-PC: ! &quot; # $ % &amp; &#x27; ( ) &lt;blank&gt; __ same! ADM-DA: ! &quot; # $ % &amp; &#x27; ( ) &lt;blank&gt; US-101: ! @ # $ % ^ &amp; * ( ) </code></pre> There may be other similarities; this is just what I noticed at a glance.

Many VTxx emulators still have this answerback function. Look in the PuTTY configuration under Terminal, &quot;Answerback to ^E&quot; (^E = ENQ).

And, if you were sneaky you could find out where someone was chatting to by sending the answer back see and if you didn&#x27;t like the computer center system programmer you could send a wall(1) with it and crash the Gandalf terminal server.

But what does the RUB key do?