“Hey, George, me and Bri and Steve are starting a gang, do you want to join?”

“Brill, I hope we get to eat sweets, talk about bikes and agree that girls are ikky.  Man, it sure is sweet being 10!”

“Welcome aboard.  I’ve made this secret code so that we can send messages to each other and nobody else will be able to read them!”

“Uh-oh, we’ll have to give a copy of this to Mrs May at number 10.”

“Why?  Who’s Mrs May?”

“Well, Harry, she’s the person that makes sure all of the kids in the street are safe from naughty children by reading all of their secret messages.  Every gang that develops a code has to give her a copy of it.  That way she can be sure that if she suspects somebody of planning to egg houses, or ring doorbells and run away, or even steal dust caps from cars she can set her dog, Bobby, on them.”

“I’m not sure I want Mrs May reading all of my messages, George.  She’s an old busy-body with 8 cats!”

“This isn’t the time for ad hominem attacks, Harry. Mrs May has already prevented dozens of bad-boy attacks on this street, and this simple measure will allow her to prevent many more. What if Bad Ali’s gang were planning to look up girls’ skirts – you wouldn’t want that to happen, would you?”

“No…that does sound bad.  Will she be spying on us all of the time?”

“She’s not spying, Harry, she’s keeping us safe and she’ll only read the messages if one of the judges from the flower and vegetable show says it’s OK.  They’ve got our best interests at heart.”

“Doesn’t her friend Michael from the village council choose who’s going to judge the flower and vegetable show?”

“The important point is that she’s keeping us all safe.  Don’t forget that.  If we don’t let her have our secret code then somebody might even steal our bikes or discover our jazz mag stash in the woods.”

“Hang about, though – my code is based on a public-private key encryption method.  If we hand it over to Mrs May then I can no longer use it to securely transfer passwords or financial information.  I can’t even trust public-key encryption signatures.  Our gang’s entire e-commerce model will be compromised and gangs from other streets will know that.”

“You’re being overly paranoid.  Mrs May has no intention of damaging our on-line security and she’d never abuse this power in that way.”

“But what if some really bad boys broke into her house and wrote down all of the codes?  They could intercept communications for years invisibly, harvesting a bank account and credit card information for everybody in the street and then clean out the lot, netting themselves billions…of, um, sweets.  Cripes!”

“Aren’t you more worried that she might find out you’ve been looking at the underwear section of the Marks & Spencer web-site and tell your mum?”

“Well I certainly am now, George.”

“Best focus on that then, Harry.  Now pop round to Mrs May’s house and leave these codes on her hall table – she usually leaves the door open.  Just make sure no immigrants see you do it.”