Vincent Gable’s Blog

August 28, 2009

Fair Coin Tosses

Filed under: Security,Tips | , , ,
― Vincent Gable on August 28, 2009

Flipping a coin is, ever so slightly, unfair. As this article (via) points out, there is a bias for a coin to land on the same side it started on.

Fortunately, all the biases coins have are systemic biases — they effect all similar coins the same way.

So, with a fair thrower, it’s possible to flip twice, and have the bias of the two throws cancel each other out.

Procedure

  1. Put a coin heads-up, and flip it, as you normally would.
  2. Note the result, if certified this will be the decision.
  3. Flip the coin again, exactly as you did in step 1.
  4. If the coin lands on the opposite side as it did in step 2, the result from step 2 is certified. Otherwise, restart from step 1.

For maximum fairness and reproducibility, it’s best to let the coin land on the floor.

Why This Works

To simplify discussion, let’s call the sides of the coin unlikely (U) and likely (L) instead of heads & tails.

There are only 4 possible results to a pair of coin tosses: UU, UL, LU, LL. Obviously LL is most likely, and UU is least likely, so we rethrow if we get either (steps 3-4). That means the only “certified” results are UL or LU, and the odds of getting UL are the same as getting LU.

Dexterous Cheating

Unfortunately, this is not a self-enforcing protocol, so if the thrower is skillful enough, they can make the second throw go however they like, and keep re-throwing until they get the result they want.

Fortunately, most people aren’t able to manipulate a coin-toss. If you are worried that someone else is, then only let them flip once, and call the result in the air — that way they won’t know which side to pick.

If you can throw the result, and can’t find someone else to call the result — it serves you right for driving away all your friends by cheating at coin tosses, you tosser. But I’m still impressed.

August 27, 2009

Prometheus 1.0 Released!

Filed under: Announcement,iPhone | , ,
― Vincent Gable on August 27, 2009

My first iPhone app is in the iTunes App Store!

PrometheusLogoChrome.png

Prometheus

App_Store_Badge_EN.png

There are many apps for reading Wikipedia. Prometheus is different. It’s an editor for the Simple English Wikipedia

Simple English Wikipedia is like regular English Wikipedia, but it’s written with simple words and grammar, so kids and non-native speakers can easily grasp it.

Features

  • Shake for a random page
  • Or search and browse with purpose.
  • All articles are formatted for iPhone.
  • Tap the words you want to change to start editing.
  • Landscape keyboard support for easy typing.
  • Unfinished edits are automatically saved for later.

Simple Wikipedia makes a complex world comprehensible. Use it to teach what you know to someone who wants to know it.

Download from the iTunes App Store

August 19, 2009

iPhone Password Correction

Filed under: Accessibility,iPhone,Security,Usability | , , , ,
― Vincent Gable on August 19, 2009

Idea: your iPhone knows your passwords, so when you make a small typo, it corrects it for you.

There are obviously major security concerns here. But I believe they can be acceptably mitigated by the phone itself. Someone would have to physically use the iPhone to get password correction, and correctly could only happen on the first or second password attempt. Also, correction could be limited to the kinds of typos a person would make.

Passwords are broken by machines, not people. I believe password correction can help people, without substantially helping machines, and compromising security.

It’s hard to type precisely on an iPhone’s virtual keyboard. That prevents people from using secure passwords, and that hurts security. Because password correction helps people actually use strong passwords, it should be to be a net security benefit.

August 16, 2009

Best First Straight Razor

Filed under: Announcement,Tips | , , ,
― Vincent Gable on August 16, 2009

As I’ve said before, I sometimes shave with a straight razor. Honestly, straight razors are worse than safety razors by just about any metric you pick1 — except the most important one: fun.

They turn a 40 second routine into a 40 minute ritual. It takes more work, to get a slightly coarser cut, but when I’m done I feel pampered yet accomplished. Kind of like if I went to an invigorating spa, but actually made something instead of relaxing.

If you are thinking about trying straight razor shaving, here’s my advice on what razor to try first.

The Good

The Hess EZY Shave Razor is the best all-around razor to see if straight-razor shaving is for you.

It’s easy to maintain, because it takes disposable blades. No sharpening or stropping required.

It has exactly the same size and ergonomics as a real straight razor.

Of course, the blade is different. But the long and stiff hair shaper blades it takes aren’t too far off.

It’s affordable, and not just the sticker price. Because, it takes easy-to-find “injector” blades as well as hair shaper blades, it’s affordable to keep using. (Tip: to find cheap injector blades, look for “mini shaper blades“, they are the same thing, but without the “key” for loading into an injector razor).

I’ve been throughly satisfied with my EZY Shave, and I still use it today. It’s handy for trimming places like the upper lip, that are difficult to reach with a safety razor.

The Bad

Actually, this is the cheap.

FROMM Hair Shapers can be had for $3 to $7. Check your local beauty supply store first, so you don’t pay more in shipping than the razor itself costs!

LIke the EZY Shave, it uses disposable hair shaper blades, so it’s easy to maintain.

This little fellow isn’t made for shaving, and it feels cheap, but when you take the guard off, it works … well enough. I’ve gotten descent shaves from one. The ergonomics aren’t exactly like a real straight razor, but they are close enough to give you a feel for what using one is like.

The bottom line is that it’s such a small investment that there’s very little risk in trying the FROMM. If all else fails, it’s still a perfectly good hair shaper. I still use mine to trim my sideburns.

The Ugly

Another good option is to ask around on forums like Straight Razor Place, and see if an old-timer will sell you a no-frills shave-ready razor on the cheap ($10-$30).

The disadvantage of starting with the real thing, is that it adds more variables, and you’ll need to get a strop to prepare the razor for each shave. (Sorry, I don’t know any good deals on strops, try a local knife shop.)

In other words, you’ll have to learn how to shave and maintain a straight razor. Bad stropping technique will dull a blade, or make it uncomfortable to use. That means more to go wrong. It also means one more thing to rule out as the cause of a bad shave, making it harder to evaluate the experience.

This is how I learned to use a straight razor. In retrospect, I don’t think it was the wisest way to go. But for many people, you haven’t tried something, unless you’ve really tried it.

1Some folks really believe a straight razor gives the closest (and yes, most nick free) shaves of their lives. I’m not one of them. I don’t think most people who’ve tried a straight razor are. That’s not to say true believers are wrong — preparing and using a bare blade give you ultimate control of every aspect of the shave. But machines still make sharper blades, while people inevitably make mistakes. And in my experience, some nooks and curves (eg. bottom of chin) can be reached better with a safety razor.

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