[coppsilgold]

To obtain the encryption key, yes.

The trapdoor method is successive squaring and relies on quite a few assumptions for its security.

The hash method also has the advantage that the sender can utilize multiple machines/cores in creating the encrypted package. By executing the serial hash task in parallel with all available resources and using the results of each chain to encrypt each other in another chain.[1]

[1] <https://news.ycombinator.com/item?id=7848999>

[sterlind]

the chained hashes approach is an extremely elegant method, thank you for linking it.