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aeternity search trends in Google
included essential applications, other possible use cases and
give intuitions for how to use the platform as a developer.
Third, we will present the current proof-of-concept imple-
mentation, written in Erlang. We conclude with a discussion,
including possible future directions and comparisons to other
A. Previous Work
Blockchains, ﬁrst of all Bitcoin, have shown a new way
to architect value exchange on the Internet . This has
been followed by a number of promising advances: Ethereum
demonstrated a way to write Turing-complete smart con-
tracts secured by a blockchain architecture ; Truthcoin
created tools for making oracles on blockchains , while
GroupGnosis and Augur showed how to make them more
efﬁcient ; Casey Detrio showed how to make markets
on blockchains ; Namecoin showed how to make the
distributed equivalent of a domain name server ; Factom
showed how a blockchain that stores hashes can be used as
a proof of exi...
also has to pay a small fee for the amount of time it is
open. The costs of creating and keeping accounts prevents
spam and disincentivizes state-bloat. The reward for deleting
accounts incentivizes the reclaiming of space.
A.3) Name system:
Many blockchain systems suffer from
unreadable addresses for their users. In the vein of Aaron
Swartz’ work and Namecoin, Æternity features a name
system that is both decentralized and secure, while still
supporting human-friendly names . The blockchain’s state
includes a mapping from unique human-friendly strings to
ﬁxed-size byte arrays. These names can be used to point to
things such as account addresses on Æternity, or hashes e.g.
of Merkle trees.
A.4) Block contents:
Each block contains the following
The hash of the previous block.
A Merkle tree of transactions.
A Merkle tree of accounts.
A Merkle tree of names.
Fig. 2. A simple hashlock.
macro Commitment a9d7e8023f80ac8928334 ;
Commitment hashlock call
if 0 100 else 0 50 end
Fig. 3. Using the hashlock to trustlessly send tokens through a middleman.
input and gives a new channel state as output
. The beneﬁts
of using pure functions in software development in general,
and in the development of ﬁnancial applications in particular,
has been extensively documented in academia and industry
for decades 
a) Contract interaction and multi-step contracts:
Even though all contracts are stateless and execute inde-
pendently of each other, contract interaction and statefulness
can still be achieved through
. A simple
hashlock is shown in ﬁg. 2. On line 1, we deﬁne a functio...
a higher nonce that both of them have signed
before the countdown ﬁnishes. If she does so, the
channel closes immediately. Otherwise it closes
when the countdown has ﬁnished.
C. Consensus mechanism
Æternity uses a hybrid Proof-of-Work and Proof-of-Stake
consensus mechanism. The block-order will be determined
via Proof-of-Work. Certain system variables will be deter-
mined via on-chain prediction market system, which allows
the users to participate and bring in their knowledge. For
the PoW algorithm we currently favor a variant of Tromp’s
Cuckoo Cycle, one which is memory bound, and also is
an ”indirectly useful Proof-of-Work”, as it requires less
electricity to run, but instead has another limiting factor,
the one of memory latency availability. This also makes it
feasible to mine with a smart phone.
Tromp writes about his work:
”[Cuckoo Cycle is] an instantly veriﬁable memory
bound PoW that is unique in being dominated by
By having prediction markets about the variables that
deﬁne the protocol, the users can learn how to efﬁciently
improve the protocol. By having predictions markets about
potential hard forks, we can help the community come to
consensus about which version of the code to use. Each user
chooses for itself which metric it seeks to optimize, but a
simple default strategy would be to maximize the value of
E.1) Sharding trees:
The architecture that has been pre-
sented thus far is highly scalable. It is possible to run the
blockchain even when each user only keeps track of the
part of the blockchain state that they care about and ignores
everyone else’s data. At least one copy of the state is needed
for new users to be certain about the substate that they care
about, but we can shard this data across arbitrarily many
nodes so that each node’s load is arbitrarily small. Merkle
trees are used to prove that a substate is part of...
B. State channel applications
Smart contracts in state channels are perfect for micro-
services on the web that require a high transaction through-
B.1) Toll API:
Most APIs existing today are publicly
available for anyone to call, or else they are secured by a
username-password–scheme or unique access tokens. Pay-
ment channels allow for a new kind of API, where one
pays for every call to the API, possibly every HTTP-request.
Paying to access an API solves DDoS problems, and it makes
it easier to build high-quality APIs that are always available.
API responses that require a payment are fundamental for the
creation of as of yet impossible types of businesses and can
play an important role in the emergence of the decentralized
economy. They create incentives for information owners to
make otherwise private data publicly available.
B.2) Insured crowdfunding:
We can implement insured
crowdfunding using dominant assurance contracts
If the market is split in time, then the attacker front-
runs the market. He reads the transactions coming into
the market and creates buy and sell orders immediately
before and after.
Fig. 6. The black line is the demand curve, the red line is the supply
curve. The sells in red are the same size as the buys in red. The vertical
line is the price the market maker selected. Everyone willing to buy at a
higher price traded at that price, everyone willing to sell at a lower price
traded at that price.
To combine markets in space, everyone should use the
same market maker. To combine markets in time, we need
to have trading done in batches, at single price. The market
maker needs to commit to each person what price he decided,
and if anyone can ﬁnd contradictory commitments from the
market maker, then all of his customers should be able to
drain all of his channels. If the market maker commits to a
fair price, then he will match the same volume ...
However, our approach has both fundamental limitations
and avenues for improvement. These are discussed here.
A. Limitations and tradeoffs
While we do believe that the tradeoffs made in our
architecture are reasonable given the resulting performance
increase in other areas, Æternity is not a catch-all solution
for decentralized applications. It should rather be viewed as
a synergistic complement to existing technologies. There are
several caveats that one need to be aware of.
A.1) On-chain state:
Despite having many advantages,
Æternity’s lack of programmable state makes it unﬁt for
applications that require a custom state to be under con-
sensus. For example, this includes DAOs as they are usually
conceived, custom name systems and subcurrencies which
are not tied to the value of an underlying asset.
A.2) Free option problem:
If Alice and Bob have a
channel and Alice signs a contract, she essentially gives Bob
a free option when she sends it...