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cryptography

This tag is associated with 7 posts

Beyond averages: DCT graphics

The visual field is full of smooth curves. Shadows don’t have sharp edges but fade out. Colours blend, sometimes imperceptibly. At some level of detail, most things transition smoothly, but to varying degrees. The variation across such transitions is noticeable in a high quality digital photograph, i.e. a pixel image. Here is a random row … Continue reading

The culture of the GIF

GIF image files have 8 bit colour for red (R), green (G) and blue (B), i.e. 256 shades each for RGB. Most smartphone cameras currently provide 10 bit colour. So if you convert your photographs to GIF format they will be of lower quality. Apart from that the GIF format provides lossless compression. So GIF … Continue reading

How to hide one picture inside another

Here’s an anamorphic image of Karl Marx in the aptly named Karl Marx House in Trier, Germany. Face on, the image is a blur. Side on you can see him. That’s one way of concealing an image, revealed only if you know where to stand. Digital images offer other methods as well. Here’s a fragment … Continue reading

Crypto-sceptics

Encryption is an unfortunate necessity to keep our personal information and communications private. While we ponder whether it’s safe or not to Zoom it’s worth reflecting on encryption’s negatives. Critic Shoshana Zuboff writes “encryption is the only positive action left to discuss when we sit around the dinner table and casually ponder how to hide from … Continue reading

Beware of this message

Generals and soldiers must pass messages up and down the chain of command in secret to avoid interception by the enemy. The same applies to cities. Writing in the 1600s, the English natural philosopher (and proto-semiotician) John Wilkins (1614-1672) affirmed that “there are certain ways to discourse with a friend, though he were in a … Continue reading

The dissimulated city

As anyone who plays video games or works with digital media will tell you, a simulation of a city is a model or image of a city. A simulated city (as in SimCity™) is similar in some respects, but not the same as a brick and concrete city. Now consider the related word dissimulation. Something … Continue reading

Sign here ……………………

How do signatures function? A signature is a sign, seal, or mark on a document indicating its authenticity, as when a painter signs a painting, or someone signs a letter or legal document. The signature and the thing it marks is meant to be a one-off. The signature marks an original document, before the thing … Continue reading

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