function arc4Bitstream(key, drop)
{
	// initialise s array to identity
	this.s = [];
	for(var i = 0; i < 256; i++)
	{
		this.s[i] = i;
	}
 
	// key scheduling algorithm
	var j = 0;
	for(var i = 0; i < 256; i++)
	{
		j = (j + this.s[i] + key.charCodeAt(i%key.length)) & 255;
 
		// swap s[i] and s[j]
		var k = this.s[i];
		this.s[i] = this.s[j];
		this.s[j] = k;
	}
 
	this.i = 0;
	this.j = 0;
 
	// ARC4-drop[n] support - recommended: 3072, compat: 768
	if(drop)
		this.getStream(drop);
}
 
arc4Bitstream.prototype.getStream = function(size)
{
	var data = [];
	for(var c = 0; c < size; c++)
	{
		this.i = (this.i + 1) & 255;
		this.j = (this.j + this.s[this.i]) & 255;
 
		// swap s[i] and s[j]
		var k = this.s[this.i];
		this.s[this.i] = this.s[this.j];
		this.s[this.j] = k;
 
		data[c] = this.s[(this.s[this.i] + this.s[this.j]) & 255];
	}
	return data;
}
 
arc4Bitstream.prototype.transformText = function(input)
{
	var bitstream = this.getStream(input.length);
	var output = "";
	for(var i = 0; i < input.length; i++)
		output = output + String.fromCharCode(input.charCodeAt(i)^bitstream[i]);
	return output;
}

I recommend any of the other well recognised and more importantly well tested javascript implementations out there if you are intending to put this into production use, as I only tried it with a couple of the wikipedia examples to check it worked. It also supports ARC4-drop[n] by use of the drop parameter when initialising a new arc4Bitstream. This helps to defend against analysis attacks which take advantage of strong indications to the key which are especially prevalent in the first bytes of the generated keystream. Also, there is no key management, that is left up to anybody who is using the code to implement, so using the same key twice will destroy your security. I don’t really know why I really wrote all this out anyway, it’s not like anybody will read it, even less likely they’d try and use it ;D

Edited 21/10/2011 when I finally realised I’d bothered doing a pair of encrypt/decrypt functions that did the exact same thing with different variable names… transformText now does both.

I pretty much ran out of posts when the local shop ran out of energy drinks. Now, the last exams of my school career and exodus to university lay on the horizon. In the next couple of weeks though, I’ll hopefully have enough time to get back into a routine of posting stuff. I’ve been working on a load of things recently.

First of all: new programming project. Trench Breakthrough: Ypres is coming back once again, and I’m rolling my own engine in Javascript, using the new features which HTML5 and related specs (basically WebGL) have made possible. I’ve been working on this for a few months now – hopefully this’ll be big enough to have some posts of its own soon

Secondly, banterous.co.uk expansion, including the new domain “bantero.us“, thanks to webhead. So far it’s been a site for sharing demos, but soon it will be a general DP:PB2 utility site, hosting demos in addition to a map database and other tools which were once provided by sk89q’s Digital Paint Resource site. The reference sections of that site will be replaced by the wiki which webhead is currently developing on the banterous hosting. f3l1x, the author of some awesome server tools is also helping out. And another developer called Payl has developed a banterous demo downloader

I’ve also been trying to finish Cold War City for release, having done another 3 betas or so.

Hell, maybe I’ll even put some content up here that is actually useful for once instead of just a brain dump. You never know

So far, so good. Of course, like pretty much any hardware device other than the very basics, you’re going to need some drivers in order to use it properly. Hercules provide drivers for Windows and Mac with full support, and also, to their credit, provide linux drivers too, with source code available, but no official support. The drivers come as .deb and .rpm packages for both 32 and 64 bit systems. So far, so good. But on attempting to install the packages, which were last updated 2009, the installation dies while the kernel module is compiled. After a bit of investigating, I found the build log and the problem:

error: implicit declaration of function ‘snd_card_new’

The source uses the snd_card_new function, which was deprecated in mid 2009 and removed soon after in favour of the snd_card_create function which allowed better error handling. To fix this, you must extract the packages, open device.c, search “snd_card_new” and replace the line:

card = snd_card_new(index[idx], card_id/*id[idx]*/, THIS_MODULE, 0);

with:

snd_card_create(index[idx], card_id/*id[idx]*/, THIS_MODULE, 0, &card);

That solves the problem with compiling. Then you can pack it all back up again and install with dpkg as usual. However, it’s a bit of a hassle, and to make it simpler, here’s a pre-baked .deb package, tested on Ubuntu 10.04 64bit. Have fun and happy mixing!

Download [x86, x86_64, .deb, 213kb]

Young Rewired State is slightly different in that the developers are all 15-18 years old, gather in centres around the country (this time there were centres in London, Brighton, Manchester and Norwich) and have a week to work on their projects. Collaborating in groups or developing alone, there was also help from professional developers as mentors. Sadly I couldn’t afford the travel costs into London for the whole week, but I was given a chance to participate anyway, working from home and just going in for the presentation event at the end of the week. James Cunningham also missed out on the mentoring, working in Dundee, but that didn’t stop him from writing a truly amazing project.

Faced with the question of what to do for a project, I wanted to incorporate real life data into a game style simulation. However, this didn’t seem very practical, so eventually I wrote a postcode comparison web tool with PHP  – enter two postcodes and it will give you a table of results comparing the two areas in a number of different categories. As each category is output in a similar way, I separated the logic for input and output from the category logic, which allowed me to easily add and remove collections of categories by adding and removing PHP classes. Some of the categories that I implemented included ADSL and Cable Broadband availability, the number of materials able to be recycled locally, the crime level compared with the national average and the Digital Switchover date.

Then, on Friday, everyone assembled in London for the presentation day, where everyone gave a short talk about their project, and, technology permitting, a short demonstration. The quality of the products was amazing; everybody had clearly put a lot of effort into polishing their projects, with lovely CSS designs everywhere you looked, which was one reason that I was apprehensive when taking to the stage. A minute long delay while attempting to get the projector to work didn’t help either.

Projects included UniSearch – a search engine for university courses, NatuSearch (a natural-syntax database search engine) by the aforementioned Mr Cunningham, an endless number of HTML5 spinners by the YRS Manchester team (who also contributed a rap!) and Isabell Long’s GovSpark site tracking government energy usage.

Overall, it was a very enjoyable experience which taught me a valuable lesson – just because you’re at home doesn’t mean you can slack off working!

An in-depth, official writeup by the wonderful people who made everything happen can be found here.

You can have a look around at www.banterous.co.uk – try not to break anything

If you’re interested in having a look at the PHP library internals, I’ll probably be releasing them some time under the GPL.

If you want to try it out without uploading the .php script, you can use “viciouz.co.uk/other” as a server address.

minivcs-0.1.tar.gz

So, um, yeah. Not much else to say. Bye.

The shortened and rather pointless music clip is: “Can You Feel The Pace” by Marc Smith & Al Storm