Like this? I'll send commit
For me this looks a bit strange, what do others think, should we add logo to overview page?
Incrementing nonce is easier (faster) than changing k.
Err, what? If you increment nonce (and I mean above the mask) you need a new k anyway.
There is no need to change k, built-in miner doesn't change it.
You forgot about SHA-2 hashing of the whole block. It will be slower and not just "slightly". By the same reason CPU mining is slower.
Not sure I follow what you mean here. The SHA is not iterated, so it is again just more cycles not more memory scheduling. The factor of performance advantage is dominated by memory bandwidth, so the relative gain should be largely unaffected. In other words, both the cpu and the gpu need to spend approximately the same extra effort there, so it shouldn't have much impact on the overall performance ratio.
You said "it will always be slightly slower than just x11 because of the added signature step". This is what I was answering, if you talk about absolute hashrate than SpreadX11 will not be as fast as X11 because of added SHA-2 hashing, if you talk about gpu/cpu ratio than it may be comparable to X11.
Some of your writings seem very strange:
then produce the encrypted signature bits as output. The pool would give the output mapping from pairs of encrypted bit values to bit states so the worker could know the output without needing to decrypt it.
Getting unencrypted value from an encypted one is exacty what decrypting is. You couldn't descrypt value without a need to decrypt it. I for sure I will read carefully all your arguments and look into how it could affect SpreadCoin. The worst thing is probably that in several years we can get some pool with very high overhead compared to solo mining.