[tromp]

There is indeed no excuse for saying "there is no" when they mean "there is no known"

It's almost as bad as saying that NP stands for Non Polynomial time.

[opheliate]

It’s probably worth remembering this is a pre-print of the paper. This is the kind of thing that would be corrected when actually published.

[cryptonector]

It could be a translation error. The author clearly does not speak English as a first language.