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Description
The State of Blockchain Interoperability in 2021 - Rafael Belchior, INESC-ID & Instituto Superior Técnico
Blockchain interoperability is emerging as one of the crucial features of blockchain technology, but the knowledge necessary for achieving it is fragmented. This fact makes it challenging for academics and the industry to seamlessly achieve interoperability among blockchains.Given the novelty and potential of this new domain, in this talk, we present an overview of blockchain interoperability, based on a survey comprising a corpus of 332 documents. Our review classifies studies into three categories: Cryptocurrency-directed interoperability approaches, Blockchain Engines, and Blockchain Connectors. Each category is further divided into sub-categories based on defined criteria. We discuss not only studies within each category and subcategory but also across categories, providing a holistic overview of this area including the most recent Hyperledger project, Hyperledger Cactus.
Sessions Details & Slides (if available)- https://sched.co/j3ai
----
Hyperledger – Open Source Blockchain Technologies
Hyperledger is an open source community focused on developing a suite of stable frameworks, tools and libraries for enterprise-grade blockchain deployments.
It serves as a neutral home for various distributed ledger frameworks including Hyperledger Besu, Fabric, Sawtooth, Indy, as well as tools like Hyperledger Avalon, Cactus and libraries like Hyperledger Aries, Ursa. Learn more about Hyperledger projects: https://www.hyperledger.org/use
Case Studies: https://www.hyperledger.org/learn/case-studies
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#Hyperledger #HyperledgerGlobalForum2021 #Blockchain
A
A
What
is
it,
what
are
the
current
solutions
available,
and
how
can
you
get
started
working
on
this
topic
as
a
side
note
if
you're
interested
in
into
interoperability,
I
encourage
you
to
also
attend
to
other
interoperability
talks,
specifically
those
from
shingo
and
peter,
from
hyperledger
cactus,
from
bandit
from
ibm
and
also
from
sarah.
That's
going
to
present
our
recent
work
on
interoperability.
A
A
A
A
Okay,
you
need
to
check
lots
of
conditions,
so
it
tends
to
be
a
niche
technology
that
it's
very
good
to
solve
a
certain
subset
of
problems.
Okay
and
this
technology
is
spread
across
hundreds
of
blockchains
which
can
answer
to
its
specific
use
cases.
Okay,
that's
value!
That's
160
billion!
It
was
the
market
cap
of
cryptocurrencies
a
while
ago
right,
but
we
can
see
that
there
is
a
huge
heterogeneity
and
a
huge
diversity
of
blockchains.
A
We
that
come
with
a
lot
of
value.
Okay.
What
does
this
cause?
The
fact
that
there
is
fragmentation
that
there
are
isolated
silos
of
data
and
value
that
is
vendor,
locking
and
the
risk
of
a
blockchain
deemed
old,
insecure
bugged,
and
the
lack
of
standards
makes
it
risky
for
enterprises
to
invest,
because
it's
a
considerable
investment.
A
These
allied
to
the
fact
that
there
are
no
data
migration
tools
available
or
at
least
general
purpose,
watching
migrators
makes
blockchain
a
difficult,
reasonable
investment
at
first
in
first
sight
and
then
comes
the
the
integration
problem.
If
we
want
to
connect
our
blocks
into
another
number
of
blockchains,
the
complexity
rises
quite
quickly
right.
So,
if
we're
connecting
every
pair
of
blockchains,
if
we
have
10
ledgers,
we
then
we
have
about
50
integration
scenarios,
but
you
can
see
that
that
number
grows
quite
quickly.
A
A
It's
very
good
at
solving
certain
problems
and
this
maturing
process
where,
where
people
start
to
understand
this
and
where
people
start
to
explore,
the
real
use
cases
are
done
in
the
so-called
unlikely.
This
is
also
where
standards
and
interoperability
is
established,
so
the
technology
can
reach
this
mass
adoption
and
reach
the
plate
of
productivity.
A
A
One
of
the
first
findings
was
that
research
trends
on
interoperability
are
rising.
This
is
not
a
big
surprise,
because
interoperability
is
and
will
be,
more
and
more
important
as
more
and
more
blockchains
exist
and
as
more
and
more
diversity
of
blockchains
exist.
So
the
number
of
search
results
on
google
scholar,
so
this
is
regarding
academic
work,
mostly
is
rising
quite
rapidly
throughout
the
years.
A
A
We
also
explore
blockchain
of
blockchain
solutions
and
hybrid
connectors
that
I'm
going
to
explain
a
bit
later,
as
well
as
architecture
for
blockchain
interoperability.
Standards
cross
chain
cross
category,
actually
analysis
of
these
different
categories,
some
use
cases
and
research
directions.
So
we
try
to
be
generating
an
holistic
view
of
this
field.
A
A
The
green
ones
are
public
connectors,
okay,
so
they
essentially
connect
public
blockchains
across
each
other,
and
we
have
three
subcategories
side
chains
and
relays
notary
schemes
and
hash
log
time
contracts.
I'm
going
to
talk
a
bit
more
about
this
in
a
bit
more
detail,
then
we
have
blockchain
of
blockchains,
so
essentially,
infrastructures
like
polkadot
and
cosmos
and
then
hybrid
connectors
that
can
connect
not
only
public
to
private
blockchains
but
also
private,
to
private
blockchain
and
even
non-public.
A
Blockchains
to
centralized
systems,
so
you
have
thrusted
relays
or
semi-trusted
relays,
blockchain
agnostic
protocols
and
blockchain
migrators,
and
then
we
classify
each
solution.
That's
on
the
references
tab
on
the
right,
according
to
a
set
of
criteria,
for
example,
in
the
asset
type
we
can
have
data.
So
it's
raw
data,
raw
bytes,
the
plus
sign,
indicates
which
ones
support
the
transfer
of
raw
data
and
the
red
ones.
The
minuses
represent
the
ones
who
cannot.
Okay,
we
have
data
payment,
tokens,
p
and
utility
tokens,
so
essentially
fungible
non-fungible
tokens
right.
A
Then
we
have
the
infrastructure,
public,
blockchains,
p
or
non-public,
blockchain,
so
private
blockchains,
other
types
of
hybrid
decentralized,
ledgers,
centralized
systems,
np,
decentralization
and
essentially
cross-chain
realization.
How
are
technically
cross-chain
transactions
realized?
How
is
the
trust
enforced
in
that
cross
chain
process?
And
there
are
several
ways
of
doing
that.
For
example,
I
am
mediated,
or,
for
example,
escrowed
cross
claim
where
you
walk
an
asset
in
a
origin,
and
then
you
unlock
it
on
the
target.
Blockchain.
A
The
first
public
connector
solution
are
such
insane
relays.
A
sidechain
is
an
extension
of
the
main
chain
that
allows
to
offload
competing
power,
so
you
can
do
different
things.
That
dimension
cannot
do
an
example
of
of
a
side.
Chain
of
bitcoin
could
be
ethereum
or
if
we
look
at
on
the
other
way
around
the
side
chain
of
ethereum
can
be
bitcoin,
because
each
blockchain
can
post
things
on
the
other,
so
we
can
offload
functionality,
and
then
we
have
relays
that
actually
are
relaying
transferring
information
from
one
chain
to
the
other.
A
A
A
A
The
second
sub
category
are
notary
schemes.
Notary
schemes
are
centralized
systems,
typically
that
perform
the
role
of
a
mediator
right.
So
in
in
case
of
exchanges,
end
users
can
give
dollars
the
exchange,
buys
or
acquires
bitcoin
another
cryptocurrency,
for
example,
and
they
give
it
back
to
the
users
in
on
their
worlds,
they're
also
decentralized
exchanges,
but
for
the
sake
of
time,
we're
not
covering
them.
A
Full-Time
contracts
are
so
far
a
very
good
way
to
perform
cross-chain
functionality
without
the
trusted
intermediary
right.
This
figure
is
from
the
cross-claim
paper
presentation,
a
very
good
paper
and
a
very
good
presentation
where
actual
time
contracts
are
are
studies
so
basically
hashtag
time.
Contract
is
a
scheme,
a
mechanism
where
two
parties
participating
on
two
blockchains
create
a
smart
contract
that
has
some
conditional
logic
for
transferring
an
asset.
A
Such
that,
if
you
provide
that
secret
okay,
actually
she
publishes
the
hash
secret.
Then
she'll
transfer
you
the
assets.
Okay,
bob
sees
this.
This
smart
contract
and
publishes
another
smart
contract
with
that
secret
with
the
same
hash:
okay,
encoded
in
the
smart
contract,
which
means
that,
if
alice,
provides
the
secret
right,
then
bob
sends
her
the
tokens
that
she
wants
on
on
that
blockchain
and
then
he
has
the
secret.
So
he
can
redeem
his
assets
on
the
other
watch.
A
Then
blockchain
of
blockchains
are
frameworks
that
provide
essentially
a
full
stack
for
creating
blockchain,
decentralized
apps.
They
are
watching
specific
apps
more
concretely
and
they
come
with,
let's
say,
free
interoperability,
because
typically
those
infrastructures
have,
as
a
mean
of
connecting
its
sub
chains,
a
relay
chain.
A
So
it's
the
interoperability
processes
are
conducted
via
a
blockchain
or
via
a
network
that
relays
transactions
and
assures
the
overall
global
state
consistency
in
case
of
polka
dot.
It's
it's
based
on
parrot
chains
that
are
essentially
shards
of
the
main
chain
that
allows
to
run
application
specific
blockchains.
A
There
are
some
entities,
some
nodes,
that
collect
the
transactions
from
there
from
each
parrot
chain
that
produce
blocks
and
that
send
the
blocks
to
the
relay
chain
and
that
that
relate
chain,
transmits
the
blocks
to
to
all
the
parachutes
or
to
the
involved
patch
chains,
and
this
allows
cross-purchasing
communication
cross-country
interoperability
between
the
several
chains.
Okay-
and
this
is
based
on
substrate-
that's
developed
in
rest.
A
This
actually
provides
a
good
level
of
interoperability
between
the
instances
of
that
infrastructure,
not
necessarily
with
other
blockchains.
Although
there
are
apparatuses
called
bridges
that
try
to
solve
this
problem,
and
then
we
have
hybrid
connectors,
it's.
There
is
a
quite
a
lot
of
work
in
this
category,
so
I'm
going
to
focus
on
trusted
relays
or
semi-trusted
relays
in
which
you
you
have
included
those
examples:
hyperledger
cactus
the
most
recent
hyperledger
projects
dedicated
to
interoperability
and
also
all
that
the
open
digital
asset
protocol.
A
A
A
So
if
we
agree
to
submit
a
transaction
to
fabric
when
something
happens
on
ethereum,
we
would
be
sure
that
if
that
condition
is
not
respected,
we
would
know
okay,
and
this
assumption
resulted
in
the
enterprise
environment,
but
other
trust
assumptions
could
be
made.
Now
there
are
different
plugins
right.
We
could
evaluate
what's
going
on
on
fabric,
we
could
connect
with
cdm
issue
transactions,
and
these
nodes
have
really
nicely
nicely
done,
sdks
that
that
clients
could
connect
to
so
we
could
build
applications
on.
On
top
of
these
clients,.
A
A
It
is
a
very
difficult
challenge
because
there
are
a
lot
of
layers
to
be
covered,
so
the
technical
and
synthetic
layers
are
mostly
technical
work,
but
on
top
of
that,
the
semantic
layers
required
a
lot
of
work
from
standardization
bodies,
so
in
particular,
what
is
the
protocol
between
two
consortia
that
rules
interoperability
between
blockchains?
What
is
an
asset
transfer?
Okay?
What
is
data
exchange
and
challenges
like
that?
A
The
open
digital
asset
protocol
tries
to
provide
the
answer
to
that,
and
then
we
have
other
layers,
such
as
the
application
layer
that
rules
out
the
domain
of
the
applications
built
on
top
of
those
protocols
and
also,
for
example,
the
legal
layer.
Other
supporting
technologies
include
decentralized
identifiers
and
verifiable
credentials
which
promote
identity
portability.
A
A
Another
concept
that
relates
to
this
is
the
blockchain
view
ongoing
work
with
my
co-authors
that
helped
on
this
paper
a
blockchain
view.
It's
essentially
a
data
abstraction
right
that
takes
place.
That
starts
in
building
a
snapshot
of
the
original
blockchain.
It
builds
something
called
a
view.
That's
a
stakeholder
specific
view
of
those
states
that
compose
the
blockchain,
and
then
we
can
do
interesting
things
with
the
views,
such
as
merging
views,
checking
differences
between
views
and
processing
views.
A
These
allow
us
to
do
interesting
things
such
as
auditing,
blockchain
migration
and
analytics,
for
example,
some
topics
I
consider
interesting
for
exploring
and
studying
the
interpretability
between
diverse
different
public,
private
blockchains,
blockchain
migration,
decentralized
identity,
standardization,
blockchain
of
blockchains
approach.
These
are
very
hot
research
areas
nowadays.
A
So
to
conclude,
botch
interoperability
is
in
expansion.
People
are
starting
to
to
study
it
and
to
realize
that
it
is
needed
for
blockchain
interpretability
to
mature,
in
particular,
such
as,
like
the
internet,
had
its
full
potential
when
we
started
connecting
local
networks.
I
believe
something
similar
will
happen
with
watching
when
we
start
connecting
them.
We'll
have
network
effects
that
so
far
we're
not
considering.
A
A
A
A
I
know
that
those
public
blockchains
are
doing
some
efforts
on
interoperating
with
each
other
right,
but
I
don't
think
that,
as
their
main
scope,
interoperating
with
private
blockchains
is
a
priority
right.
So
hyperledger
has
also
multitude
of
projects
right.
So
fabric
is
one
of
the
most
popular
it's
it's
private,
so
I
don't
think
they're
doing
that
effort
to
solve
this
question.
We
have
several
interoperability
projects
such
as
cactus
and
weaver,
to
make
fabric
in
particular
to
interoperate
with
cardano.
A
A
Right
there
are
some
more
questions,
one
from
igor.
What
is
the
best
way
to
start
exploring
and
investigating
blockchain
interoperability?
Okay,
that's
a
very
good
question
that
I
I
also
had
when
I
started
my
studies
in
2019
at
the
time
there
was
some
work,
that's
true,
but
it
was
very
fragmented.
It
is
still
a
bit
fragmented.
Actually
because,
as
I'm
writing,
this
survey,
things
are
evolving
quite
quickly
and
it's
very
difficult
to
catch
up,
even
if
you're
only
doing
that.
A
Grail,
each
literature
like
white
papers
out
okay,
I've
tried
to
cover
that
as
well,
but
there's
so
much
material
nowadays
that
it's
difficult
to
keep
up.
So
if
you
know
those
basics,
those
projects
that
are
the
core
that
are
a
bit
older,
then
I
think
that's
a
good
basis
for
understanding
the
the
area
in
general.
A
A
A
A
So
this
is
ongoing,
work!
Okay,
it's
not
it's
very
recent.
It's
actually
not
published,
so
the
idea
is
that
each
stakeholder,
each
participant
on
a
blockchain,
has
a
different
view
or
may
have
a
different
view
of
a
blockchain
okay
in
private
blockchains.
This
is
in
public
blockchain.
So,
let's
start
there,
it
happens
with
temporary
forks
right
where
we're
different
nodes,
and
we
temporarily
see
different
chains
right.
Eventually,
we
choose
the
right
one,
but
those
different
forks
might
provide
provide
different
information
that
we
could
reason
about
right
in
private
blockchains.
A
So
the
idea
here
is
to
collect
the
individual
specific
view
of
each
stakeholder
right,
so
we
can,
for
example,
compare
them
and
see
understand
what
one
what
one
stakeholder
can
see
at
each
moment
of
time
and
the
other
cannot.
Okay.
This
is
very
useful
for
auditing,
for
example,
if
you
want
to
migrate
a
blockchain
solution.
This
is
also
useful
because
we
want
all
the
stakeholders
to
be
agreeing
on
the
state
to
be
migrated
right
and
if
they
cannot
access
the
same
state,
that's
a
problem.
A
A
There
at
the
moment,
there
needs
to
be
some
sort
of
trust
level
between
the
networks
that
are
interoperating
right
or
between
the
gateways
that
are
connecting
those
those
networks.
So
in
case
of
odep,
the
open
digital
asset
protocol
that
we're
developing
at
the
internet
engineering
task
force.
The
assumption
is
that
the
gateways
are
trusted.
The
gateways
are
not
lying
because
there
are
accountability
mechanisms
that
keep
track
of
of
their
actions.
A
A
So
interoperability
requires
trust
assumptions,
okay,
because
it's
actually
extending
trust
right
between
partners.
So
some
some
scenarios
require
more
trust.
Other
scenarios
require
less
trust,
it's
specific
to
the
solution
right,
and
this
also
partially
answers
the
next
question.
What's
the
most
difficult
thing
into
interoperability,
and
I
believe
that
one
of
them
is
to
set
boundaries,
set
the
right
boundaries,
the
right
trusted
sanctions
and
enforce
the
right
behavior
in
the
protocols
and
and
nodes
that
are
conducted.
Such
processes,
it's
still
all
pretty
recent,
all
pretty
new.
So
it's
difficult
to
get
that
right.