Quote from: AussieHash on April 06, 2014, 06:09:37 PM

I wonder how much of this bad luck turn is due to external influences?

Somebody is DDOS eligius, and recently succeeded in a NMC payout hack against the pool. I also have noticed BTCGuild, Ghash and Blockchain showing the cloud flare error in the past few days.

Quote from: wizkid057 on April 03, 2014, 10:43:17 PM

A semi-well known fact about me: my real life job includes DDoS mitigation at the ISP level for multiple ISPs.

This particular attack against Eligius has taken almost every form possible... UDP reflection attacks (DNS, NTP, SNMP, etc... 30+ gigabit at times), TCP SYN attacks (over 20 gigabit peaks), botnets directly flooding pool ports (multiple gigabit), botnets attempting application layer (stratum and HTTP) attacks (varies up to several gigabit and > 100k connections), HTTP request floods from botnets and other amplification (wordpress being one), hanging TCP connection attacks, various attack attempts against public facing bitcoinds, flood attacks against upstream routers, social engineering attempts (someone has contacted the abuse@ addresses for some nodes claiming Eligius is DoS attacking them, lol, presumably in an attempt to stir trouble with our hosts), and probably a ton of other things that are just automatically filtered/ignored.

https://bitcointalk.org/index.php?topic=441465.msg5986935#msg5986935

Luck for eligius and BTCGuild are both well under 100%
https://bitcointalk.org/index.php?topic=441465.msg6077549#msg6077549

Unknown pool is rapidly growing share, up to 33 34%
http://blockchain.info/pools?timespan=48hrs

And there maybe an unknown binary Merkle tree weakness being used (where the included transaction count are base 2). Now even if the weakness is theoretical, this is severely delaying confirmation times.

https://blockchain.info/blocks/80.241.217.46
http://www.reddit.com/r/Bitcoin/comments/22cohy/8024121746_mining_18_blocks_today_containing/
http://reddit.com/r/Bitcoin/comments/20y0nq/why_do_all_the_blocks_hashed_by_unknown_miners/

Would a faster-to-calculate power of 2 Merkle tree make a selfish attack slightly more effective ?

Luck has nothing to do with any of the above, it's just... luck.

The only thing that miners can do is a block withhold attack and without a PPS pay scheme the miners stand to lose if they do this, though with a large enough pool they may be willing to sacrifice some income leaving the other miners to subsidise their mining. Unlikely but not impossible. Theoretically pools may have implemented block withhold detection techniques but the pool ops would never reveal if they were not because that would then be opening themselves up to this attack. Attack is a very strong term though since there's so little to gain from doing this, it's not worth dwelling on it any more.

Merkle tree size choice has no effect on luck nor can it be used in any kind of attack. It's just a crappy optimisation for inefficient code.