Currently, an attacker can 51% attack the network with roughly
60% of SHA256D and nothing else. After this change, an attacker with
90% of the SHA256D hashrate and
33% of each of the other 4 algorithms would have insufficient hashpower to mount a 51% attack. Is this true? Source:
https://github.com/digibyte/digibyte/pull/36 So in theory a attacker does not need to have some hashrate in all 5 algorithms (used in marketing of digibyte)? 60% of SHA256D is sufficient?
That's my pull request, here is an up-to-date calculation.
Based on current difficulties (averaged over 1000 blocks), this is each algorithms contribution to the work calculation:
sha256d: 1.13e+06 * 1
scrypt: 23.7 * 4096
groestl: 152 * 512
skein: 1070 * 24
qubit: 47.6 * 1024
This adds up to 1.38e6. Half the total can be made with just 61% of the sha256d contribution. Asics are to blame. When the formula was crafted, each algorithm did indeed have a near-equal contribution. But as the sha256d hashrate climbed the others couldn't keep up. It was always true that an attacker could attack the coin with just 1 algorithm but they would have needed at least 87% if all algorithms were weighted properly. The new formula does not rely on magic work factors, and does not allow one algorithm to dominate under any circumstances.
I'm not going to throw stones at marketing. As far as I can tell they didn't know it was wrong. Now we know, but already have a fix to make it even stronger than the original claims.
MentalCollatz would be the proper authority to answer this. And yes, at the time of our first hard fork to multi algo we did not know this formula was incorrect. We are always working to improve things. We have worked in his changes to the upcoming DigiSpeed hardfork that will make things much better.
Also @Mental, we would love to chat some time and run some ideas by you we have for modifying OP_RETURN. Thanks for stopping by and answering this!