BlockChain News
between blocks differs from the expected
time by 7%, a worrying figure that is in-
tensified by the coin-hopping attack. The
paper reads:
If you want to understand how this new
difficulty adjustment algorithm can work,
make sure to read the “Revisiting Difficul-
ty Control for Blockchain Systems” paper.
More information about the Ergo Platform
“In this paper we also consider a new type can be found here.
of miner behavior with regards to difficul-
ty adjustment which provides an unfair
Dmitry Meshkov will present this work
advantage to the miner, and also makes
during a blockchain workshop associated
inter-block delays worse. We call the dis-
with ESORICS’2017: http://www.deic.uab.
covered strategy the coin-hopping attack.” cat/~jherrera/CBT/.
In this attack, miners switch from one coin
to another in the beginning of an epoch
(difficulty retargeting event), switching
back to the first one in the beginning of
the next epoch when difficulty becomes
lower.
This means that the miner leaves coin1 to
ensure that mining difficulty is reduced
by the lack of his presence and goes on
to mine another coin2, returning to coin1
once the difficulty re-targeting period has
made mining easier again. This means
that until the next epoch, the network will
not adjust to the presence of the miner.
The paper adds: “Remarkably, under such
an attack the mean time between blocks
in both chains will be bigger than the
planned time.”
In order to fix these issues, an Improved
Difficulty Adjustment is proposed: An al-
gorithm that is both resistant to the afore-
mentioned attack (and others that may
be based on difficulty manipulation) and
that allows for an almost constant desired
block rate under real-life circumstances.
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