These are md5 checksums. Commonly used when downloading Linux files, including when you download a full operating system, the md5 checksum is also often posted along with the file, it’s used to verify that it is the authentic file and you got an uncorrupted download. Basically just a text file, compared with the one embedded in the download.
What some people are mistakenly referring to, dead man switch, is entirely different. If Assange were actually dead, we’d most likely be looking at every file he had uploaded online immediately. Something like those used in movies sometimes, you’ll see the character with something in his hand that looks like a simple switch, if he quits holding it down, kablooooie...
I’m willing to bet Assange has a digital version, my guess would be if he doesn’t check his computer and input a specific security code at specific times every day, it’s automatically distributed. So if and when he dies, he misses the next check in time and we’ll have everything at once, or a notice will be sent to associates for them to either immediately distribute in full or take over scheduled delivery.
Could be done by physical means too. Hold this, do not touch. If you read my obituary, let it loose. One 2TB external hard drive could hold millions of the emails we’ve been seeing. Maybe billions. Most text emails are so small a hundred can fit on a floppy. 1.14MB is a floppy. 1GB is a thousand MB. 1TB is a thousand GB...if your average email is less than 200KB...usually a lot less...this entire text message, if pure text, wouldn’t be 100KB.
Recall the scene at the Cyberdyne building in Terminator 2

If a program could be written to scan newspapers for obituaries or 'missing person' it could also stop the incentive for kidnapping and torture. Thanks to all for explaining 'hash'... comforting that freepers understand. Fighting the machine's going to get harder - - we'll need our best minds for the battles ahead.