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From YouTube: The Blockchain Bridge That You Dream About
Description
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https://archive.devcon.org/archive/watch/6/the-blockchain-bridge-that-you-dream-about/index
In the times where scalability of blockchains depends on multiple layers, and when interoperability holds for an essential blockchain feature, bridges become critical infrastructure parts. They are meant to hold liquidity, asked to operate quickly, but they cannot benefit from the security guarantees of an on-chain application, because they inherently contain off-chain components. In this talk, we discuss the properties of a bridge that is secure and meets all the needs for it to be useful.
Speaker(s): Martin Derka
Track: Layer 2s
Keywords: Bridge,Security,L2
Follow us: https://twitter.com/efdevcon, https://twitter.com/ethereum
Learn more about devcon: https://www.devcon.org/
Learn more about ethereum: https://ethereum.org/
Devcon is the Ethereum conference for developers, researchers, thinkers, and makers.
Devcon 6 was held in Bogotá, Colombia on Oct 11 - 14, 2022.
Devcon is organized and presented by the Ethereum Foundation, with the support of our sponsors. To find out more, please visit https://ethereum.foundation/
A
A
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.
A
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
send
me
the
assets
that
I
want
to
have
bridged
the
way
how
this
really
happens.
A
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.
A
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
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.
A
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.
A
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.
A
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.
A
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.
A
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.
A
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.
A
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.
A
Imagine
a
mixer
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.
A
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,
but
that's
probably
not
going
to
be
fast.
A
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
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.
A
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,
QR
code
leads
to
a
paper
about
security,
hacks
and
incidents
and
bridges.
That's
everything,
I
had
to
say.
If
you
want
to
talk
to
me
during
Defcon
or
anytime
later,
this
is
telegram.
Thank
you.