The rsync algorithm (1996) [pdf]

doodlesdev 7 hours ago | parent | next [-]

Well-written, succinct.

This small document shows what computer science looked like to me when I was just getting started: a way to make computers more efficient and smarter, to solve real problems. I wish more people who claim to be "computer scientists" or "engineers" would actually work on real problems like this (efficient file sync) instead of having to spend time learning how to use the new React API or patching the f-up NextJS CVE that's affecting a multitude of services.

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PunchyHamster 4 hours ago | parent [-]

to be fair level of security of systems back then was pretty fucking bad

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axiolite 13 minutes ago | parent | next [-]

In 1996? OpenBSD and Apache had been around for a year. PGP had been around for several years. HTTPS was used where needed. SecurID tokens were common for organizations that cared about security.

Admittedly SSH wasn't around, but kerberos+rlogin and SSL+telnet was available. Organizations who cared about security would have SecurID tokens issued to their employees and required for login.

Dial-in over phone lines, and requiring a password, was much less discoverable or exploitable than services exposed to the internet, today.

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observationist 3 hours ago | parent | prev [-]

6 characters or fewer passwords, if there were passwords at all. Phreaking still worked into the 90s, and all sorts of really stupid things were done without really thinking about the security at all. They'd print out receipts with the entire credit or debit card number and information on it, or carbon copy the card with an impression, and you'd see these receipts blowing around parking lots, or find entire bags or dumpsters full of them. Knowing an IP address might be sufficient information to gain access to systems that should have been secured. It's pretty amazing that things functioned as well as they did, that society was as trusting and trustworthy as it was, that we were able to build as much as we did with as relatively a tiny level of exploitation that happened.

If the same level of vulnerability was as prevalent today as it was back then, civilization might collapse overnight.

	▲	mjevans 21 minutes ago \| parent [-]
		To be fair, back then it was relatively easy for anyone intelligent enough to be able to abuse any of that to have a well paying 'white collar' job with things like full health benefits, a pension, and more than sufficient income to support an entirely family SOLO. They even owned houses! When your life is set like that why risk trying to defraud someone a the cost of a nice suit when that's something that can be done legally and written off as a business expense on taxes?

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teleforce 23 minutes ago | parent | prev | next [-]

Fun facts, the author of rsync, Andrew Tridgell, is also the one who reverse-engineered Microsoft SMB that laid the foundation for Samba [1].

How he did manage to avoid lawsuits from Microsoft is beyond me.

[1] Server Message Block:

https://en.wikipedia.org/wiki/Server_Message_Block

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craftkiller 2 hours ago | parent | prev | next [-]

I've been using this extensively recently. I was setting up remote virtual machines that boot a live ISO containing all the software for the machine. Sometimes I need to change a small config file, which would lead to generating a new 1.7GiB ISO, but 99.9% of that ISO is identical to the previous one. So I used rsync. Blew my mind when after a day of working on these images, uploading 1.7GiB ISO after 1.7GiB ISO, wireguard showed that I had only sent 600MiBs.

Fun surprise, rsync uses file size and modified time first to see if the files are identical. I build these ISOs with nix. Nix sets the time to Jan 1st 1970 for reproducible builds, and I suspect the ISOs are padded out to the next sector. So rsync was not noticing the new ISO images when I made small changes to config files until I added the --checksum flag.

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bix6 an hour ago | parent | prev [-]

Funny timing, I just used this today while setting up my NAS