MacGuffin

A seemingly important but ultimately trivial plot element that exists purely to facilitate the telling of the story. The term was coined by Alfred Hitchcock, who employed McGuffins with relish.

McGuffins are commonly found in in genre movies; thrillers, adventures, comedies and such. The characters must arrive at position A or problem B, and the McGuffin is there to see that they do. McGuffins are plentiful and easy to spot, but here are some examples:

• Everything in Psycho prior to the appearance of the Bates Motel, specifically Janet Leigh's involvement in the theft of $40,000. The larceny is a McGuffin that serves to deliver Leigh to the motel.
• The briefcase in Pulp Fiction, which is very important to many of the characters, but beyond giving them something to search and kill for, makes no contribution to the movie.
• Similarly, the diamond heist in Reservoir Dogs.
• Whatever it is that distracts Macaulay Culkin's parents in any given Home Alone film.
• The dead body in Stand By Me.
• The mob killing in Some Like It Hot
• The Maltese Falcon itself.

McGuffins are a regular feature on The Simpsons, where it's not uncommon for the first act to be devoted to an elaborate setup for the main plotline (e.g. the soccer riot that leads to Homer buying a gun). The use of a McGuffin is often acknowledged in the show with a self-deprecating comment; Hitchcock, too, was not above drawing the audience's attention towards irrelevant plot elements.

The McGuffin can be thought of as a variable in the plot: Indiana Jones faced a great deal of peril in his quest for the $mcguffin. Lost Ark? Temple of Doom? In true McGuffin style, it's not where the audience is going, but how they get there.

MacGuffin is a block cipher algorithm, similar to DES, that takes a block of 64 bits of text to encrypt, takes a secret key that is 128 bits long, performs its transformation based on the key, and produces as output 64 bits of text that should be unintelligible to anyone who doesn't have the secret key. It is one of Bruce Schneier's early block cipher designs, which he created with Matt Blaze, and presented in the December 1994 Fast Software Encryption proceedings. It is an unbalanced Feistel network with 32 rounds, similar in structure to the NSA's Skipjack algorithm in this respect, that attempts to use mostly operations that were cheap on the 16-bit microprocessors that were most common at the time, and could be used as a drop-in replacement for DES. The name of the cipher comes from the acronym of the class of ciphers to which it belongs, i.e. the Generalized Unbalanced Feistel Networks, GUFN's, hence MacGuffin.

Vincent Rijmen (of AES/Rijndael fame) and Bart Preneel performed a cryptanalysis of MacGuffin and showed that it was quite vulnerable to differential cryptanalysis and linear cryptanalysis, but also showed it could be significantly strengthened by making only a few minor changes in its use of S-boxes. This happened during the same workshop MacGuffin was presented.

It was never intended to be a cipher for wide practical use, as Schneier and Blaze state in their paper: "As its name suggests, MacGuffin is intended primarily as a catalyst for discussion and analysis," as the cipher incorporated a new and as yet untried method in cipher design. Otherwise, Schneier and Blaze would have been far more embarrassed by Rijmen and Preneel's findings!

JULES
You win.
Jules raises his hand off the briefcase.

JULES
It's all yours, Ringo.

PUMPKIN
Open it.

Jules flips the locks and opens the case, revealing it to Pumpkin but not to us.
The same light SHINES from the case. Pumpkin's expression goes to amazement.
Honey Bunny, across the room, can't see inside.

HONEY BUNNY
What is it? What is it?

PUMPKIN
(Spoken softly) Is that what I think it is?

Jules nods his head: "Yes."

PUMPKIN
It's beautiful.

Jules nods his head: "Yes."

 

Throughout the movie Pulp Fiction, characters have been influenced by a mysterious briefcase owned by the big crime boss Marcellus Wallace. This plain black object is found in the opening sequence when Vincent and Jules recover it from some bumbling criminals.

The briefcase is an example of a MacGuffin, sometimes spelled McGuffin or Maguffin. We know that it is important because bullets were exchanged and lives were lost in its recovery.

So, what is it?

The answer is, it really doesn't matter.

No, seriously. The simple briefcase is there for one purpose — to begin the story or plot. The audience doesn't really care about the briefcase because they're more interested in what the characters are doing.

Quentin Tarantino even pokes a little fun at the audience in the ending scene, excerpted above. When Jules opens the case and shows the contents to Ringo/Pumpkin, all we (the audience) know is that the case is valuable and, now that it's opened, it gives off a mysterious glow that takes everyone's breath away. Now we want to know what is in the briefcase, but Jules slams it shut and wraps up the scene and the movie. We never find out what was the impetus of over two hours of craziness. Don't believe me? Just Google "pulp fiction briefcase" and enjoy 174,000 hits and lots of pages with different theories, including Kryptonite and Marcellus' soul.

The joke was on us, which made the movie even more memorable. It also helped to spur debates as to what was in there, which helped to get the word out concerning the movie.

MacGuffins have been around for a while. The concept can be seen in many old stories, such as the Holy Grail or a certain black bird in a Bogart movie. The purpose of a MacGuffin is to provide a method to get the plot rolling, and the object can be anything external. A big pile of cash or even vague concepts such as glory and honor can be used to begin the tale. The plot revolves around the characters, while the MacGuffin is really ignored for the most part once the story is kickstarted in high gear.

Alfred Hitchcock was well known to use this device to begin his movies starting back in The 39 Steps. Adventures and thrillers used MacGuffins extensively in order to have the story moving along as quickly as possible. Even the original Star Wars: A New Hope uses stolen plans inside R2-D2 as a MacGuffin. Everyone is running around looking for the plans hidden in the little droid. The chase evolves, and in this case so does the MacGuffin's container — into a beloved iconic character. The data gets extracted at the end of the movie and the final battle against the Death Star commences. 

Sometimes a MacGuffin can take on a life of its own. Those stolen plans from R2-D2 ended up as a complete movie: Rogue One.

A MacGuffin is a little white lie that the audience or reader plays along with to get to the fun part of the journey. After all, a story about a briefcase would be rather boring, with it being worried about scuffs or how its hinges could use a spot of oil, thank you very much. The hand that holds the briefcase, however, can be a thrilling and satisfying tale.