What’s in that USPS postage barcode?

pbSmartPostage test stamp

I am publishing this post as a hobbyist, because I find barcodes cool (as demonstrated by a prior open source project using 2D barcodes that I worked on). Do not attempt to use this information for any illegitimate purpose. Counterfeiting postage is a federal crime. 18 U.S.C. § 501.

This post ties together some of my favourite things: 2D barcodes, high speed automation, printers, cryptographic signatures (!), postal mail and postage, fraud prevention, and even a little bit about patents!

Continue reading “What’s in that USPS postage barcode?”

Dear HP


To whichever engineers at Hewlett-Packard decided that it would make sense to pollute our frequencies with unneeded ad-hoc printer wifi networks enabled by default… You messed up.

Now every university dorm has to cope with unimportant personal printers putting out stronger signals than the nearest real access point. And houses in residential neighbourhoods receive neighbours’ printer signals more strongly than the high-power N/AC router.

I get that owners can connect them to routers instead of being separate APs. But guess who’s not turning off this “feature”? All of your least tech savvy customers.

(Side note: Comcast’s wider deployment of cable modem-router devices in homes and businesses with secondary xfinitywifi hotspots produces the same issue when customers are plugging in their own wireless routers right next to the Comcast device. I love using xfinitywifi, but there are real issues unless Comcast has configured these hotspots to scan for surrounding networks before deciding whether to broadcast a signal. And again, while there may be an opt out option, it’s the least tech savvy users who don’t turn it off, who generate potential interference for their neighbours. Negative externalities!)

It bothers me that the current default is a situation where tech-dumb people piss off tech-smart ones.