foreign
[Music]
hi everybody thank you for coming my
name is Martin I'm from Quan stamp I'm a
senior research engineer and the head of
new initiatives and I will be telling
you about the properties of bridges that
I really like
so before I do that we should all
understand what a bridge really is right
so let me do that so when I say a bridge
I kind of sort of want you to understand
this type of an architecture we have two
chains my mother chain for you know all
intent and purposes this will be
ethereum and then we have another chain
and we want to get our assets from one
chain to the other chain so for this
purpose we have something that I call a
custodian this is where me will lock
some assets some ether then we have an
off chain component called a
communicator that is going to be
watching what I have locked in the
custodian and it's going to instruct
some liquidity pool on the other chain
to uh send me the assets that I want to
have bridged the way how this really
happens the first case by case some
bridges issue some debt tokens some
bridges work with real liquidity pool on
the other chain and just send me the
assets then this was the deposit on the
withdrawal the process is exactly the
opposite so the communicator is actually
going to be watching the debt issuer
where I will be burning my tokens the
data tokens and that then is going to
instruct the custodian to send me back
the eth that I want to have a bridge
back okay so this is the mental model
that I want you to maintain when I speak
about bridges so now I'm going to give
you the properties the menu of the
properties that I like uh about bridges
when they have them so first of all we
develop Bridges because we have other
chains many of the other chains are sort
of trying to speed up ethereum right but
you know if the bridge takes ages to
bridge my assets from one chain to the
other one then this is not really the
user experience that I want to have so
what I really want from a bridge is the
speed
then the next thing that I really want
is finality that means that once the
assets are bridged from one side to the
other one or from the other side back
this is final nobody is going to reorg
nobody is going to bring those assets
back they are just not going to
disappear
the next next thing that I really
appreciate is atomicity so that would
mean that there is no moment in time
where I do not hold the assets I have
them on one chain and then as soon as
this bridging happens atomically I
suddenly have them on the other chain
there's nothing in between where the
world could stop where an asteroid could
hit the earth and I could lose my asses
because you know I have nobody to call
or something like that but this is
actually really hard there is something
called Atomic swaps but you know that's
a really really complicated protocol so
you know Thomas city is something that I
long for but it's really hard to
accomplish then you know very obviously
I want my purchase to be secure because
nobody really likes losing assets if you
do please talk to me after the talk you
must be a very special kind of a human
being but we usually want the bridges to
be secure
then what do we long for in general in
the web 3 space is censorship resistance
that means that anybody should be able
to use the bridge
then we certainly also want availability
meaning that it doesn't matter whether
it's 10 AM or 10 pm or 1am or whatever I
should be able to use the bridge right
now if I wish to do so
then I also want liveness liveness means
that if I instruct the bridge to move
the assets from one chain to the other
chain at some point this is going to
happen the bridging will never get stuck
on the other hand sometimes we also want
possibility because if one of the chains
is in troubles you know there is a hack
there or the bridge itself has problems
then sometimes it really helps when we
can stop the time when we can freeze
everything and do some crisis resolution
or something like that right
next thing that I really want is
liquidity so you know I might be a very
rich person I might choose to today
Bridge 100 million dollars and if I
choose to do so I would really like to
be able to do so and that can happen
only if the bridge is sufficiently
liquid
uh the next thing that I like to have is
what I call expressive power so I want
to be able to bridge my native assets
that means ether but I also want to be
able to bridge a bunch of stable coins
and other tokens right maybe nfts so all
the erc20s erc721s ERC 1155s what I'm
really saying here I want the bridge to
actually be able to perform cross chain
smart contract calls
then I want my purchase to be cost
efficient because you know I don't like
to spend money on gas right but
sometimes we don't really have the
option to do anything about that because
we're interact interacting with two
chains the transactions have to be paid
for on both the chains right but it
would be nice if the bridges were not
adding any additional cost overhead to
that
then privacy is also often desired
imagine a mixer uh where you know I send
money in on one chain
and they magically show up on the other
chain in a different account
and nobody can connect the transactions
together
and then the last thing that I really
like is transparency and disability that
means that if I'm watching the bridge at
any point of time I can convince myself
that the bridge is actually functioning
properly that it is not you know sending
money around without any reason without
it being instructed to do so
so this was the menu now the main point
of this lightning talk is this is
actually really hard
there are always conflicts between all
these properties that we would like to
have for example speed and finality
they are conflicting if I want my bridge
to be final or the bridging process to
be final then finally has to be reached
on Two Chains independently right uh but
that's probably not going to be fast
similarly if I'm talking about
availability and pausing well once a
bridge gets paused it's not really
available right it's not accepting any
transactions I cannot bridge at this
moment same thing with security and
liquidity sometimes uh you know bridges
are really liquid but we don't really
like to have all the assets sitting in
some smart contract that potentially
could be exploited on one or the other
chain right so therefore Bridge
operators very often limit the liquidity
they take the assets they move them into
some escrows cold wallets and similar
things so there are always a bunch of
trade-offs you have to pick and choose
what you are going to implement this
slide is actually you know screaming
with QR codes so this QR code leads to
our talk from each Denver about security
incidents in bridges and this particles
uh QR code leads to a paper about
security hacks and incidents and bridges
that's everything I had to say uh if you
want to talk to me uh during Defcon or
anytime later this is uh telegram thank
you
[Applause]