ROT13: good version

by amptorn • 7 years ago

44 22 7 years ago

ChrisSD3• 7 years ago

Technically ROT13 can only handle 26 characters. The "good" version would be to deny any inputs outside an accepted character set.

Ok so this doesn't really matter for a joke algorithm like ROT13 but in more serious cases it's important to refuse any inputs that aren't handled and not try ad-hoc fixes to make them "work".

A2017U1• 7 years ago

Can a cipher invented 2000 years ago have a technical standard ascribed to it?

ChrisSD3• 7 years ago

Caesar ciphers? I believe they are well defined, yes. Although ROT13 itself only dates back to maybe the 70's or 80's.

Besides, I was honestly just using this as an excuse to make a more general point. I've grown frustrated with bugs and security issues arising from "fixing" input to work in a domain which was not designed to handle that input.

But as I said, it doesn't really matter with ROT13 because it isn't a serious algorithm.

throwawaymath• 7 years ago

If it's sufficiently well-specified, sure, why not?

mseidl• 7 years ago

ROT26 is 2x as secure.

aequitas• 7 years ago

I still prefer 3rot13.

amptorn3• 7 years ago

This is a classic entry-level security mistake. You have to pick a work factor k and then do 2^k iterations of ROT13.

anon4242• 7 years ago

k=1 FTW!

dsr_3• 7 years ago

øbol comes through as øoby.

Rot13 is not defined for characters outside [a-zA-Z].

runxel• 7 years ago

German "ß" works neither (which could at least be substitued with "ss").

maxheadroom• 7 years ago

Neither does (æ or Æ).

amptorn3• 7 years ago

Just out of curiosity, what would you expect ø to encode to?

dsr_3• 7 years ago

When I said rot13 isn't defined outside of a certain set, I meant it. If you want ø to be half-rotatable, you need to specify an ordered character set (with an even set size) and say that rot29 or rot128 or whatever you come up with is the analogous mapping to rot13.

Now, rot13 excludes punctuation and keeps capitalization after transform, so an ordinary human can learn to read rot13 English reasonably fluently. I don't know if that is common across all Latin-descended alphabetic languages, but it's really not going to be a plausible skill in Mandarin.

https://en.wikipedia.org/wiki/Chinese_characters#Indexing is somewhere between horrifying and fascinating.

On the other hand, Korean (Hangul) has a perfectly reasonable alphabetic set size and ordering, at least in South Korea. https://en.wikipedia.org/wiki/Hangul#Alphabetic_order -- so I expect that Koreans can learn to read rot12.

dveeden2• 7 years ago

But emoji is not handled correctly, the cleartext and ciphertext are identical

xeeeeeeeeeeenu• 7 years ago

rot8000[1][2][3] is a similar idea.

[1] http://rot8000.com

[2] https://news.ycombinator.com/item?id=18495518

[3] https://news.ycombinator.com/item?id=6659687

ROT13: good version

Related Stories