# It's like a double yellow line

From Worse Than Failure, a story of public key cryptography:
Near the end of a technical interview, Paco H. was asked a rather blunt question from the candidate he was interviewing: "Hey, be straight with me. How am I doing?" Paco replied with the truth: not too well. The candidate was a bit disappointed, so Paco gave him a chance of redemption.

Paco: So, tell me, what are you great at?
Candidate: What am I good at?
Paco: No, no. What are you *GREAT* at?
Candidate: Hmmm. (a few seconds pass) Cryptography!

Fortunately, Paco knew a thing or two about cryptography, and knew where to begin a line of questions.

Paco: Ok. Well let's just start with the basics. Tell me the difference between asymmetric and symmetric cryptography.
Candidate: Well, the way I see it is like this. The symmetric cryptography is like when you're driving down the road and there's a dotted line down the middle and cars are going both ways. Asymmetric cryptography is like when there's a double yellow line.

Outstanding!

That's not the difference?