For the grains of sand thing, here's a technical explanation of that: https://core.telegram.org/techfaq/UoL-ETH-4a-proof#4-attacking-the-key-exchange-appendix-f

For the grains of sand thing, here's a technical explanation of that: https://core.telegram.org/techfaq/UoL-ETH-4a-proof#4-attacking-the-key-exchange-appendix-f https://core.telegram.org/techfaq/UoL-ETH-4a-proof#4-attacki... This document seems like a better response to the theoretical problems the researchers found.