
The Solitaire Encryption Algorithm (1999) - jstrieb
https://www.schneier.com/academic/solitaire/
======
cyphar
Another "paper and pen" cipher that was published a few years ago is ElsieFour
(a modified version of RC4)[1].

One of the nice things is that it even offers a form of authenticated
encryption, though it is a very string-and-staples approach. The idea is that
you would append every message with some secret text that the recipient would
know to look for (if the ciphertext is modified with ElsieFour/RC4 all
subsequent characters become garbage). In theory you would include the hash of
the plaintext but humans aren't great at computing hash algorithms in their
head.

Obviously these kinds of ciphers have lots of serious problems (awful timing
attacks for instance :P) but I think they are a key example we can point to
when arguing that banning (or restricting) encryption software is a fruitless
measure to stop "the bad guys" from using encryption.

[1]:
[https://eprint.iacr.org/2017/339.pdf](https://eprint.iacr.org/2017/339.pdf)

------
dang
Related from 2015:
[https://news.ycombinator.com/item?id=10473491](https://news.ycombinator.com/item?id=10473491)

2012:
[https://news.ycombinator.com/item?id=4904260](https://news.ycombinator.com/item?id=4904260)

~~~
vmilner
See also: [https://arxiv.org/abs/1909.06300](https://arxiv.org/abs/1909.06300)

