[benchaney]

> the known plaintext attack breaks pretty much every crypto system

This isn't true at all.

[mSparks43]

aside from aes and its varients, which of the other thousands of crypto systems arent vulnerable to it?

[benchaney]

None of the other AES finalists were vulnerable to known plaintexts attacks. Neither is 3-DES or chacha20. DES and RC4 are now considered insecure, but in their day they were resistant known plaintext attacks as well.

Other than some toy examples, and cryptosystems that were used before cryptography was studied academically, I can't think of any that are vulnerable to known plaintext attacks.