notes

Q1. Pregenerating the blinding factors.

test8.py L2371
```
bfSellerIn = sha256(bfOutSeller + bfOutBuyer + b58decode(sxSeller))
```

Neat trick to reduce the round of communication, we need to know the blinding factor in "advance".
Instead we allow the buyer to pick it and create an "intermediate" tx with predetermined blind factors.

The intermediate tx also prevents another issue, the initial blinding factor is known to a third party.
Alice (random) -> Bob (buyer) -> Carol (seller).
If we imagine the situation where _only_ the seller would generate an intermediate tx - reusing the 
initial (third-party known) blinding factor could be a security issue.

Seeing that bfOutBuyer from the new intermediate tx is randomly generated, wouldn't sha256(bfOutBuyer)
technically be enough?