The Lair of the SlowFox

MD5 is a hashing algorithm that attempts to verify that a given file's integrity hasn't been compromised (during a download process, or in the process of being copied from A to B etc).

Typically, you'll have a file reference given on a web-site and, somewhere else (this is important, more later), there'll be a long string of seemingly random characters called the MD5 Sum, or MD5 Hash or whatever:

c59b048c992804d165aed10170f003dc

What happens is that the algorithm works through the source file, and maps the first element to something new, and then feeds that result into part of the computation for the second element, and then the result of that into the third element etc. When it reaches the end of the file, the whole result gets fed back into the algorithm again. And again, and again for a specified number of iterations (loops). The end result of these calculations boils down to the specific MD5 Sum for the file.

I use WinMD5Sum on the work PC:


The idea behind MD5 hashing is that even tiny changes in the original file result in significant differences in the end MD5 hash.

For example, I created a text file called hello.txt, which contained the phrase Hello, world..

The MD5 sum of this worked out to be 45d2c2d506211d17f99a3eb8de863f36

By changing the last character to a comma - Hello, world, - the MD5 sum changed to c59b048c992804d165aed10170f003dc, immediately telling me that the file's changed from the original.

An MD5 sum is always 32 characters long, yet can be generated for files of any size. Pretty obviously, then, there will be various different kinds of files that result in the same hash - these are known (with the industry's predictable fondness for dramatic vernacular) as 'collisions'. Nonetheless, the risk of collision is pretty small (if, for example, by repeatedly going through the MD5 hashing algorithm, all files eventually boiled down to a single value, it'd obviously be useless) - that said, boffins have managed, now, to successfully construct amended files that generate the same MD5 hash, but this requires a fair bit of work and an accommodating starting point.

Anyway, the idea is that you see a file - exciting_prog.exe - on a website and download it. By using an MD5 checksum, you can verify (beyond reasonable doubt) that the file you've downloaded is the file that the website intended you to download.

(which, by the way, is a loooooooooooooooooong way from saying it's safe).

The major caveat should be obvious: the situation where the file's MD5 sum is listed in the same directory as the file itself. Consider: if nefarious malfeasants have managed to hack the server and place a malicious file in the benign one's place, then since they've clearly got access to the server, it'd be trivial for them to also replace the posted MD5 sum with the sum to match their own malicious file.

I managed to get all the way to work this morning before realising, with weary resignation, that I'd brought the wrong keys with me: vis, the castle/car key combo rather than the castle/office combo.

I do this deliberately, have separate castle and work keyrings, so as to encourage me not to use the car to commute. Which works fine, except for when I leave the house in a mild hurry on a Monday morning, and simply take the nearest set of keys to hand.

So I head to plead with the cleaner to let me into my office.

D'oh!

Standing in a gradually rising puddle whilst having this morning's shower convinced me that the drain needed clearing out in the yard. This is not a fun job, and despite my best efforts at trying to separate grungy water from fox, there was some cross-contamination, which I was less than thrilled about.

The problem is that the drain itself has a plastic 6"x6" cover that sits in a recessed square in the concrete... unless a curious hound sees it. For some reason, Mali takes an active dislike to the plastic inserts being in the drainage channels, so he flips them up with his paw, and then carries them across the yard to put them down. He doesn't chew them(!), he just feels that the yard is more aesthetically pleasing sans drainage grates.

What then happens is that rubbish and the like that blows into the yard flutters down the opened gulleys, resulting in me pulling out plastic bags and chocolate bar wrappers that have been blocking the channel.

Flow is somewhat improved, but I'm going to have to come up with a more long term solution - ideally, I'd like to find some metal grids, in the hope that they'd be sufficiently heavy to resist canine interference. Otherwise, I might try and screw down some wire mesh across the top, to make them fully tamper-proof.

Leo Laporte announced on last week's Windows Weekly that he was going to stop drawing a salary from TWiT's advertising revenue, and instead only take funds via the network's listener contributions.

I really like TWiT, and I've mentioned before that I make a monthly donation to the network basically just to demonstrate my appreciation of the service that Leo and the crew put on, and to reward high quality, well produced, entertaining and information discussion.

As Leo himself states, he can still make a living from the income off his radio show, so although it's a ... bold move, the stakes here aren't exactly riches or ruin. Nonetheless, I think this is an interesting experiment on his part, and I hope that it works out for him.

So, towards the end of the walk in this morning, I'm on one side of the road and there's a schoolgirl walking on the other, a little way ahead (say 20 metres or so). She looks over her shoulder, and sees me.

Well, we then both take the next turning, and again this girl looks behind her, and evidently notes that I'm still there, and I can almost see the cogs in her mind concocting nefarious purposes for my presence.

As (bad) luck would have it, our routes continue along the same path for the next few turnings (which is unsurprising - there's a school behind my building), and by now this poor girl is checking her back every few seconds, and looking rather freaked.

I honestly don't know what to do. Stop? Turn back? I figure that any activity other than maintaining my normal route's going to look suspicious, so I'm trying, as far as the physical constraints of street geography allow, to keep as hard to the divergent path of our routes as I can (there's a shortcut I can take through between some buildings off to the right, when I know that she's going to bear off to the left), and making sure that I don't get any closer than that first sighting at about 20 metres.

Of course, now I'm walking on the road rather than the pavement (sidewalk in US parlance), because this particular stretch only has pavement on one side, and although I'd chosen to do this to signal my intention clearly that I'm about to head off to the right, the girl keeps on looking behind her, evidently trying to fathom when, exactly, I'm going to pounce.

Eventually our paths diverge, and hopefully the girl will realise that I'm not actually some evil stalker of d00m, but all the fearful backward glances in my direction, and her obvious discomfort over my (consistently distant) presence does have a cumulative accusatory effect, and I get to my desk feeling somewhat unclean :-(

Depressing start to the day.

I may have mentioned before that Work II's heating installation is a little sub-optimal. Indeed, it doesn't even seem to be a digital installation (it'd be either ON or OFF). Oh no, my friends. We get ALL HEAT ALL THE TIME.

Colleague S has grown a little concerned about this, fearing that spending all day in a slow-cooker isn't the most comfortable of accommodations, so he's brought in a nursery thermometer, so that it's possible to keep an eye on things.

Which is how I know that the office was 24°C this morning, which after the walk in through an admittedly mild December morn, felt plenty baking enough, thank you.

I have therefore taken the executive decision to activate the cooling cycle by opening the window. Unfortunately, the windows don't like being open, so we have to prop the thing using a spare PCI riser card (Geeks R Us™) - colleagues similarly afflicted elsewhere in the building use empty milk cartons, magazine racks or screwdrivers. There's an irony to the fact that we have mumble-thousand pounds worth of kit strewn hither and yon, yet we have to prop open the windows (to compensate for the lack of operational thermostats) with whatever junk we can find to avoid melting into pools of goo at our desks.

In the customary fox-like manner of preparedness, P and I went to pick up tools that, in all probability, would have proved much more useful yesterday. Still, next time, I am totally sorted.

Anyway, B&Q, I learned to my cost, has taken to broadcasting covers of songs over the internal PA.

Not just any old covers, mind. Excruciatingly bad covers of really good songs.

Songs like Perfect (Fairground Attraction), Fast Car (Tracy Chapman), I Knew You Were Waiting (George Michael and Aretha Franklin). What makes things all the more painful is that the cover artistes are evidently trying to stamp their own personal authority through their warbling, and thus you're 'treated' to the most bizarre renditions of said ditties.

Poor P was watching me literally wince in pain as each successive travesty launched a fresh assault on the bastions of reason, good taste and ... well, just plain fair play.

P was only at Castle Fox until lunchtime yesterday - he had a party to go to Saturday afternoon, and for a change ex and co came to Hull to pick him up, rather than me ferrying him back. Unfortunately, ex not having much practice in the commute, sort of underestimated the time it would take to get here, and ended up being an hour late. But hey, all good in the end.

Today saw me venture into town at lunchtime, just as the skies went almost completely black. I caught a single glimpse of lightning off in the distance, but it would seem that the weather wasn't really that interested in putting in the requisite effort for a storm proper, and instead just contented itself with a spot of rain.

Mali and I have had a couple of brisk walks around the Avenues - if I move quickly enough, he'll walk to heel almost perfectly. And he maintained that for a little while as I attempted a light jog, but patience isn't that dog's strong suit, and he eventually went into Race Mode, so we called a literal and metaphorical halt on that one. But I'm going to try and add some light jogging into the standard walks every now and again, and see how that goes.

Bookwise, I'm currently reading (or trying to read) One Red Paperclip by Kyle MacDonald. This is the tale of that guy who traded items sequentially on CraigsList, starting off with the object of the book's title, and moving ever on up until he managed to trade himself into a house. The parenthetical hesitancy is due to the little 'zen wisdom' nuggets that pepper the end of each chapter. Since we're currently on one chapter per trade, and we're at him having acquired a camping stove, I'm somewhat fearful for my sanity, should I have to endure too many more observations of the calibre of 'now was two words ago' (I actually make that five, and so does Kyle himself in the paragraph explaining this gem, which makes the paragraph's title all the more bizarre).

Anyway, since Christmas is coming up, obviously this is the time of year when I buy myself stuff, and so I now have Assassin's Creed II for the 360... I know all the hype this year is about Call of Duty: Modern Warfare 2, but I am hopeless at FPS titles (seriously, Colleague N lent me Gears of War once, and I couldn't make it out of the training level without being killed. Repeatedly).

So expect the book-reading to tail off a bit as the year closes ;-P