Thursday 26 January 2017

Understanding Base64 Encoding #2

Tier 2

If Tier 1 is about establishing the scantest familiarity with a subject – hoping to avoid looking glassy-eyed whenever it’s mentioned – then Tier 2 is about beginning to understand the topic; perhaps a cursory interest has been kindled and/or you’d like to be able to do a bit more than just identify the subject by sight.

To that end, one of the first questions I like answered when getting to grips with a new topic is “why does this thing exist?”. I’m going to begin to attempt to answer this question for base64 encoding by giving a disingenuous, rather long-winded, somewhat tortured analogy. I promise I’ll make amends in later tiers.

Imagine a strange parallel universe in which inter-computer communication has never happened. The parallel universe’s computers work in the same manner as ours, just no one ever bothered to invent the technologies which allow computers to communicate: no Internet, Bluetooth, portable digital devices – no floppy discs, CDs, DVDs, USB drives, etc. Essentially, each computer is a lonely digital island.

In this reality, if I create a super-cool bitmap image in the alternative universe’s version of MS Paint, you’d physically have to come over to my house and look at it on my screen; I have no digital means by which to transmit the data to you. To add to my misery, you live on the other side of the country and, despite my enthusiasm and entreatment for you to come visit, you’re not going decamp for the sake of one bitmap image.

So, scratching my head, I begin to think about the problem and in a fit of pique I come up with my first – and worst – solution to this problem: I’m going to write the binary code out on pieces of paper and send the code in the post to you. Every single one and zero. And then when you receive the paper full of bits you can key them all in at your end and recreate the image. Perfect!

However, I soon find, even if I only wanted to send the small 10 x 10 pixel image from Tier 1 it’s ~1000 bytes. And given there are 8 bits in a byte that’s ~8000 ones and zeros I’ll have to transcribe! I’m not so keen on this and imagine you’re even less keen about having to key 8000 binary digits in at your end. We need a shortcut.

I’m convinced the part about mailing you the code still has merit but I’m also certain that raw ones and zeros aren’t the answer. What I need is some sort of shorthand way of representing the same raw binary data; I need to encode it.

This is the essence of the problem base64 encoding looks to solve: how can a text-based medium, in our case pieces of paper, be re-purposed to effectively transmit binary data.

Tier 3 will, hopefully, begin to straighten this all out…

Next >> Understanding Base64 Encoding #3

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