This wizard is using the PGP Word List, a way of representing numbers as strings of words, which should be easier to remember, or at the very least easier to pronounce and transcribe.
Each word in the wizard’s spell (which is randomly generated and varies for each person) can be interpreted as a single byte according to the PGP Word List system. If you do this, you will be given a command line for Brian Warner’s magic-wormhole utility, specifying a command you can type in in order to open a wormhole and download a file. (The magic-wormhole program and Warner’s explanations of it refer a lot to the idea of wizards using magic spells to create secure “magic wormholes” from one place to another, through which files might be transferred between devices.) The use of the PGP Word List is not a coincidence here, because magic-wormhole also uses the words in this list to create its wormhole identifier codes!
The file that you’ll receive through the wormhole you create contains this brief dialogue, in which Alice and Bob talk about somehow encoding some other message inside a dialogue:
[Alice and Bob are relaxing with a nice confidential session after a
hard day of SPAKE2 calculations.]
Alice: Phew, that was a lot.
Bob: Yeah. Hey Alice, did you ever read _Gödel, Escher, Bach: An Eternal
Golden Braid_ by Douglas R. Hofstadter?
Alice: Yes, I read it right after it won the Pulitzer Prize. It was a
great read.
Bob: Do you remember the self-referential dialogue where the two characters
were talking about how they could use weird properties of their
conversation to convey information?
Alice: Yeah, didn't they have something about how they would use weird
language or say something out-of-character in order to show that
the dialogue ended?
Bob: Yep! Anyway, I would never do something like that.
Alice: That's too bad. It might be fun!
Bob: Well, I don't mean that I would never convey a secret subtext in a
conversation based on weird things the conversation partners said.
Alice: Oh good.
Bob: I just wouldn't do Hofstadter's thing about having the conversation
secretly end before it seems to.
Alice: But you would use some other kind of gimmick.
Bob: Absolutely.
Alice: Will you let me know if I ever end up in a conversation like that?
Bob: I'll try to Warner you somehow.
Alice: When that day comes, I hope people will have access to full
transcript of our conversation in order to unravel the secret.
Bob: Yes, I'd personally be pretty upset if someone tried to make me figure
this kind of thing out without access to the text of what we said...
it would be such an incomplete puzzle otherwise.
Alice: That makes sense. Speaking of puzzles, do you remember that great one
that used the North Atlantic Treaty Organization's spelling alphabet?
Like "Alpha, Bravo, Charlie...".
Bob: Personally, I wish they had started with "Alice, Bob, Charlie" instead
of "Alpha, Bravo, Charlie". Somehow I can only ever remember those
things through to X-Ray. I can never remember Yankee. Oh, but I can
usually remember Zulu, because of the time zone.
Alice: But the time zone is named after the NATO letter rather than the other
way around!
Bob: Wait, Alice, what did we just say there?
Alice: Um... I don't know, I'd have to look at the transcript of our
conversation to be sure, really.
Bob: OK. Well, would you practice the NATO alphabet with me sometime?
Alice: What are the magic words?
Bob: "Please"?
Alice: Maybe some _other_ magic words?
As you might imagine, they are doing exactly the kind of thing they are talking about—once again using the PGP Word List!
They start at the point where Bob says
Bob: I’ll try to Warner you somehow.
and end at the point where he asks
Bob: Wait, Alice, what did we just say there?
In between, each of them is responsible for one of the only four times in the whole dialogue when a PGP Word List word is used:
transcript of our conversation in order to unravel the secret.
Bob: Yes, I’d personally be pretty upset if someone tried to make me figure
that used the North Atlantic Treaty Organization’s spelling alphabet?
usually remember Zulu, because of the time zone.
These words, again, correspond to byte values in the PGP Word List system:
unravel = 0xEF
upset = 0xF3
Atlantic = 0x0E
Zulu = 0xFF
The combination of these is the answer, EFF30EFF.