1. (And I think that 5 times safer from a marketing standpoint is good since we're working with 5 algos - from the most simplistic theoretical vantage point, you need to gain 51% control of 5 algos instead of 1 algo, and that is 5 times safer in spite of the fact that it's not mathematically 5 times when the 5 are considered as one joint value. Correct, or not?
2. Also, the diff of all the algos rises and falls in correlation with one another: if the sha256d diff rises, the diff on the other 4 algos rise correspondingly. Correct, or not?)
Good questions! I will try to answer 2 of them (as how i understand it, or is the community not allowed to answer technical questions? If so, i apologize and will stop answering them)
1. 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. All algorithms are not weighted properly in Digibyte and thus only 61% on SHA256D is sufficient to attack Digibyte. If these problems get sorted (all algorithms weighted properly) then you an attacker can still attack Digibyte with only 87% with just 1 algorithm. How is that 5 times safer from a marketing standpoint? It is not true that you need to gain 51% control of 5 algos instead of 1 algo. So not correct.
2. No also not correct. This is one of the flaws MaNI was talking about:
I don't want to go into too much technical details but most of the flaws revolve around the fact that 'difficulty' is a somewhat arbitrary measurement, while it can be used to meaningfully compare two blocks from the same algorithm to one another, there is no real relation between the difficulties of two different algorithms. i.e. It is not really meaningful to say that a 500 difficulty Scrypt block is worth more or less than a 500 difficulty Groestl block.https://bitcointalk.org/index.php?topic=554412.msg11804113#msg11804113 You still need an average of 51% over the 5 algos. From an easy to understand point of view, why is it technically incorrect to say that DGB is 5 times safer then?
I'm very interested is seeing how the 5 algos are not weighted correctly. On a smoothed average over time there is a 28.64 ratio to individual network hashrates and their corresponding diff (hashrate / 28.64 = diff). That ratio rises as network hashrate rises, and falls as the hashrate falls, of course, since it is an algorithm too, but averaged over time, it's a pretty good rule of thumb. That means that if one algo's hashrate and corresponding diff rises substantially, so do the diffs for the other 4 algos since they all are linked to the same ratio
that will automatically adjust higher as one individual network hashrates rises (even if each of the rest of the algos' hashrates remain stable at the time of the notable rise in the other algo's hashrate). Of course, as stated above, the actual block discovery over time supports this as no one algo ever achieves notable differences in actual block discovery.
As sated in this article from Coin Brief
http://coinbrief.net/what_is_myriadcoin/ it's not just a substantial majority of hashrate in one of the algos, but a substantial majority COMBINED with important hashrate control in the other 4 algos:
"As each algorithm controls only 20% of the network, a 51% attacker would need to control an average of 51% of each algorithm to successfully attack the network. For example, if someone brought in enough ASICs to capture 80% of both SHA256 and Scrypt, which would be very difficult on its own, that would still only amount to 32% of the overall network. The remaining 19% would need to be carved out of the Qubit, Skein, and Groestl algorithms, and there are no ASICs in development for any one of those."Add: Perhaps there is some confusion about "weighting". The algos are indeed weighted differently so that mining is "fairer" for all. The idea was to create a level playing field for all participants. This however, does not adversely affect the individual diffs: as the diff for one algo rises, so do the rest.