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From YouTube: Zcash + Ethereum = ❤
Description
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https://archive.devcon.org/archive/watch/2/zcash-ethereum
This presentation focuses on how Zcash uses zero-knowledge proofs to add private transactions to a public blockchain, and how Zcash and Ethereum will grow together. Zcash is a new cryptocurrency that provides private transactions — the sender’s and receiver’s addresses are not publicly visible in the blockchain, nor is the amount transferred. Zcash posts that private information to the blockchain in encrypted form, and uses zero-knowledge proofs to cryptographically guarantee the validity of transactions without exposing the private information. This results in “Selective Transparency”. It’s not all-dark-all-the-time — it’s that each encrypted transaction in the blockchain can be revealed by its creator to selected third parties. Zcash is developed by a VC-funded, highly skilled development team and a widespread and active open source community. There are three paths forward for integrating Ethereum’s programmability with Zcash’s privacy. The Zcash team is actively contributing to all three paths. 1. Programmable Zcash — add Ethereum-style programmability to the Zcash blockchain 2. Private Ethereum — add Zcash-style privacy to the Ethereum blockchain 3. Project Alchemy — interoperation between the Ethereum and Zcash
Speaker(s): Zooko Wilcox
Skill level: Intermediate
Track: Privacy
Keywords: immutability, encryption, communication, selective, dicslosure, human rights, society, fungibility, data, security, bitcoin, zksnarks, zkproofs, validators, programmability, alchemy, btcrelay
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 2 was held in Shanghai, China on Sep 19 - 21, 2016.
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
A
I'm
really
happy
to
be
here
a
little
bit
intimidated
by
all
you
folks.
My
name
is
Zuko
and
I'm,
the
founder
of
the
Z
cash
project
and
the
first
half
of
this
talk
is
about
what
Z
cash
is
and
the
second
half
is
about
ways
to
connect
Z
cash
with
aetherium
Z
cash.
First
of
all,
it's
a
science
discovery
that
has
been
made
over
the
past
four
or
so
years
by
a
set
of
cryptographers
and
I'll.
A
A
A
Lastly,
it's
a
community
because
there's
a
whole
bunch
of
people
spread
out
around
the
world.
Who,
like
me,
think
that
privacy
is
a
really
critical
value
in
our
society,
and
this
is
a
critical
moment
and
that
we
have
the
opportunity
to
change
the
course
of
history
for
the
better
and
that's
the
that's.
The
ZK,
the
Z
cash
community
and
the
main
reason
I
came
here
to
Def
Con
was
to
try
to
establish
more
contacts
between
the
Z
cash
in
the
etherium
community.
A
Okay.
So
what
is
cool
about?
Blockchain
technology
is
a
the
append-only
property
which
we
call
immutability
and
the
single
source
of
truth
effect,
and
you
all
appreciate
this
pretty
well,
but
this
is
really
new.
This
was
just
recently
discovered
and
we're
only
at
the
very
beginnings
of
figuring
out
what
you
can
do
with
those
two
properties,
and
this
conference
is
really
the
cutting
edge
of
experimenting
with
what
you
can
do,
given
a
append-only
in
canonicity
and
then
the
encryption
modern-day
encryption
is
like
4000
years
old,
and
so
it's
better
understood
and
pretty
much.
A
Everyone
understands
the
privacy
property
that
encryption
gives
you,
which
is
that
if
two
people
want
to
communicate
and
there's
some
third
party
who
has
some
position
of
power
with
respect
to
those
two
people,
the
two
can
use
encryption
in
order
to
prevent
the
the
other
third
person
in
the
middle
from
spying
on
or
changing
the
contents
of.
What
they're
saying
to
each
other.
That's
privacy
and
slightly
less
widely
appreciated
is
the
selective
disclosure
property
of
encryption,
and
this
is
just
a
property
of
this-
is
just
an
outcome
of
mathematics.
A
Is
that
if
you're
using
encryption
to
control
read
access
to
your
data,
then
that
means
there's
some
secret.
Some
decryption
key,
that
is
knowledge
of
that
secret,
is
necessary
and
sufficient
to
get
read
access
to
the
data
right.
But
that
implies
that
if
you
know
that
secret,
you
could
choose
to
share
that
decryption
key
with
someone
else
and
if
you
did
so
that
would
give
them
the
ability
to
see
that
data.
A
So
that
means
it's
in
order
to
really
understand
what
you
might
be
able
to
do
with
Z
cache,
what
kind
of
like
products
or
programs
you
could
build
on
top
of
it.
You've
got
to
up
the
selector
disclosure
part,
because
people
often
who
are
more
familiar
with
the
privacy
consequence
of
encryption,
they
think
of
Z
cache
as
being
like
the
opposite
of
Bitcoin
and
aetherium
or
Bitcoin.
80
theorem
are
all
transparent
all
the
time,
and
so
they
think
of
Z
cache
as
being
like
all
opaque
all
the
time.
A
It's
all
dark
all
the
time,
but
that's
not
true
at
all.
With
Z
cash
you
can
append
data
to
the
blockchain
and
that
data
is
encrypted
so
that
so
by
appending
it
to
the
blockchain
you're,
not
revealing
it
to
everyone
in
the
world.
But
if
you
selectively
reveal
it
to
a
certain
person
that
person
gets
to
see
that
data
in
the
single
source
of
truth
in
the
canonical
blockchain.
So
you
can't
you
get
you
get
the
append
only
in
canonicity
properties.
A
You
can't
change
your
story
later
and
you
can't
tell
one
story
to
one
person
and
a
different
story
to
a
different
person,
but
at
the
same
time
you
have
control
over
who
sees
the
data.
So
that's
really
interesting
and
we're
even
more
at
the
beginnings
of
experimenting
with
what
you
could
do
by
leveraging
these
properties
I
really
have
no
idea.
I
still
haven't
figured
out
what
we're
going
to
do
with
Bitcoin
and
ethereal
much
less.
With
this.
A
A
But
then,
when
I
got
started,
I
was
pleasantly
surprised
that
businesses
are
really
strongly
demanding
this
kind
of
data
security
for
their
applications-
and
this
is
true
both
of
industrial
blockchain
businesses
like
banking
and
trade,
finance
and
insurance
and
healthcare
and
Internet
of
Things,
and
so
on.
There's
a
whole
conference
on
this
topic
after
this
conference,
at
which
I'm
also
speaking
and
those
kinds
of
applications
where
they
want
to
use
blockchain
technology
for
one
of
those
applications.
Every
single
one
of
them
requires
improved
privacy
before
they
can
use
blockchain
technology.
A
One
of
our
supporters,
Jeff
garsik,
says
if
Samsung
and
Apple
can
see
each
other's
transactions,
then
that
prevents
them
from
doing
business.
We
need
a
neutral
playing
field
where
people
can
connect
with
their
partners
and
customers
at
the
same
time
as
having
privacy
from
competitors
or
criminals
or
hackers
or
whatever.
A
So
that
turns
out
to
be
really
important
and
widely
demanded
by
businesses,
which
I've
learned
in
the
last
two
years
when
I
started
talking
to
them
after
I
started
this
working
on
this
and
lastly,
fungibility
fungibility
is
the
property
that
to
101
notes
are
worth
exactly
a
hundred.
Each
one
is
worth
exactly
101.
It's
not
that
some
notes
are
worth
a
little
more
in
some
notes
are
worth
a
little
less
and
that's
really
important,
because
you
want
commerce
to
be
frictionless
and
easy.
A
You
have
enough
problems
already
getting
you
know
getting
business
done,
and
so
you
don't
want
people
hesitating
and
calculating
about
which
particular
note
they're
going
to
use
for
which
purpose
or
anything
like
that.
Fungibility
is
really
important,
and
in
the
modern
blockchain
era
we
need
better
privacy
in
order
to
keep
having
funds
ability.
In
my
opinion,
all
right,
the
way
we
do
privacy,
like
I,
already
alluded
to
encryption.
A
So
the
cinder
address
the
recipient
address
the
amount
any
other
metadata
that
is
part
of
the
transaction
that
all
gets
encrypted
and
then
only
the
ciphertext
is
posted
to
the
blockchain.
Okay.
That
clearly
has
a
very
strong
privacy
consequence,
but
there's
also
a
major
problem
with
it
like.
Why
didn't
Satoshi
do
that
years
ago,
with
Bitcoin.
Is
that
if
you
encrypt
all
the
transactions,
then
how
do
the
validators
know
how
to
discriminate,
how
to
filter
out
bogus
transactions
and
include
only
legitimate
transactions
in
the
blockchain?
A
So
that
was
the
unsolved
problem
until
about
three
years
ago,
when
the
scientists
that
I
mentioned
that
was
the
breakthrough
and
it's
called
ZK
snarks,
which
Vitalik
mentioned
in
his
talk
today
about
as
a
future
a
potential
future
improvement
to
aetherium
ZK
sinorix
are
really
efficient,
zero
knowledge
proof
and
a
zero
knowledge.
Proof
is
a
pretty
mind-boggling
thing,
but
the
effect
of
it
is
you
can
make
a
cryptographic,
a
string,
a
proof
and
the
validators
can
inspect
this
and
they
can
say
to
themselves.
A
That
transaction
is
what's
inside
this
ciphertext,
so
the
validators
can
use
the
zero
knowledge
proof
to
persuade
themselves
cryptographically
that
there
must
be
a
valid
transaction
signed
by
the
person
who
owned
the
private
key
inside
this
encrypted
transaction,
but
they
don't
learn.
Anything
that's
called
ZK
is
short
for
zero
knowledge
because
they
don't
learn
anything
else
about
the
transaction.
They
don't
learn
anything
about
the
amount,
the
other.
What
kind
of
contract
is
involved
or
anything
like
that?
So
that's
the
science
breakthrough
that
has
just
come
out
recently
so.
A
For
the
rest
of
this
talk
different
ways
that
aetherium
and
z
cash
can
connect
with
each
other.
The
first
way
so
etherium
is
reason
for
existence
is
programmability
and
z.
Cash
is
reason
for
existence
is
privacy,
and
so
we
want
to
we're
wondering
we
easy
cashiers
have
been
because
we
love
you
theorem,
we've
always
loved
aetherium.
Since
the
moment
I
heard
about
it
just
slightly
before
the
first
public
announcement
of
it,
and
so
we're
going
to
try
to
figure
out
how
do
you?
How
can
you
combine
programmability
and
privacy?
A
So
the
first
way
is
add
privacy
into
e
theorem
and
there's
this
this
hack,
that
we
did
called
Baby
Zoe
and
it's
called
baby,
because
it's
just
a
baby
step.
It's
just
a
proof
of
concept
and
Zoe
is
short
for
Z
Kashani
theorem,
some
Z
cashiers
went
to
a
hack,
fest
and
Vitalik
was
there
and
helped
them,
and
some
people
from
Cornell
we're
helping
them
and
what
that
does
is
add
a
Z
case,
norik
pre-compile
into
aetherium
and
then
implement
kind
of
a
minimal,
simplified
version
of
z
cash
as
an
ethereal
contract.
A
That's
pretty
awesome
that
that
were
and
that's
hopefully,
the
basis
of
the
coming
ZK
snark
precompile.
That
should
be
added
into
theorem
proper,
and
the
second
thing
you
can
do
is
add
programmability
into
Z
cache.
We
don't
have
any
results
to
talk
about
yet,
but
some
of
our
scientists
spend
some
of
their
spare
time
in
the
lab
poking
at
different
kinds
of
programmability
or
smart
contracting.
A
That's
what
we
call
project
alchemy
is
to
make
the
Z
cache
and
any
Theory
Emblaze
interoperate,
so
that
there's
a
seamless
ability
to
move
between
the
two
and
the
way
we
want
to
do
that
is
just
by
cloning.
Btc
relay
BTC
relay
is
an
etherium
script
that
Joseph
Chow
and
others
have
written,
which
makes
basically
a
Bitcoin
light
client
inside
a
theory
amande.
So
our
project
is
to
change
that
to
make
a
Z
cache
light.
Client
inside
of
a
theory
own
and
JD
hess
from
consensus
has
helped
with
this
already
and
sorry.
A
So
there
was
never
an
opportunity
for
either
side
to
take
off
with
the
other
side's
tokens
and
there's
just
a
little
bunch
of
complicated
like
game
theoretic
problems
that
arise
from
that
which
Joseph
Chow
has
thought
a
lot
about.
I
hope
I
mean
he
seems
to
have,
and
hopefully
we
can
just
benefit
from
all
of
that
research
and
also
I,
think
the
Raiden
design
also
tries
to
solve
the
same
problem.
So
maybe
we
could
use
that
or
its
solutions
instead,
but.
A
The
end
result
of
that
is
two
things:
if
you
get,
if
you
get
that,
if
we
get
that
working,
we
get
two
things
out
of
it,
and
this
is
the
one
I'm
most
excited
about
out
of
the
three
ways.
These
are
all
cool
and
we're
contributing
to
all
of
them,
but
the
one
that
I'm
most
excited
about
is
number
three,
because
that's
the
one
that
can
be
deployed
and
people
could
start
using
it
and
building
on
it.
The
soonest
I
think
so.
A
If
we
get
this
deployed,
the
first
thing
is
a
decentralized
currency
exchange
right
there.
So
if
all
the
currency
exchanges
have
failed
or
if
you
live
in
a
country
where
you
can't
use
a
currency
exchange
or
something
like
that,
but
you
still
have
aetherium
and
z
cash
blockchains.
You
can
use
this
to
swap
ether
for
z
cash
with
no
third
party
and
nova
more
extravagant.
A
And
you
know
if
that
were
to
get
bootstrapped
and
become
widely
used,
then
it's
one
of
those
unshut
downa
Balcon
of
things.
It's
a
general
purpose
utility
for
everyone
to
rely
on
after
that.
Maybe
I
love
the
idea,
but
the
other
thing
is:
if
that
gets
going.
If
you
have
those
contracts
on
the
ethereum
blockchain,
then
that
means
aetherium
contracts
gain
a
new
power.
A
This
is
the
awesome
thing
about
a
few
in
which
I
don't
understand
very
well,
but
the
exciting
thing
about
it
is
that
every
time
someone
adds
a
new
contract
to
the
ethereum
blockchain,
this
gives
all
the
other
contracts
the
possibility
to
do
something
new
without
without
as
much
coordination
and
planning
between
the
different
coders.
So
if
we
succeed
at
getting
this
done,
then
all
the
other
aetherium
contracts
gain
the
ability
to
send
and
receive
Z
cash.
A
Basically,
because
you
can
always,
you
can
always
post
a
claim
saying,
as
in
e
theory
on
tracked,
you
can
always
post
an
offer.
Saying
I
will
pay
you
if
you
send
Z
cash
there
or
whatever,
and
if,
if
your
aetherium
contract
receives
Z
cash,
then
if
it
were
sent
encrypted
on
the
Z
cash
blockchain,
no
one
can
tell
where
it
came
from,
but
they
can
always
see
who
has
control
of
it.
Now,
because
the
etherium
contracts
don't
have
any
secrets
right,
so
everyone
can
see,
one
interfering
contract
knows
and
what
it
decides.
A
So
if
it
decides
to
send
Z
cash,
everyone
can
see
to
what
address
it
intended
to
send
it.
So
it
could
potentially
have
privacy
on
the
incoming
transaction
and
not
on
the
outgoing
transaction.
But
that's
ok,
because
privacy
is
a
social
system,
wide
network
property.
Anyway,
it's
not
an
atomic
property
of
individual
transactions.
So
much
so,
basically,
it
seems
like
it
might
make
if
your
name
contracts
able
to
send
and
receive
more
or
less
privately.
A
Well,
we
haven't
been
making
much
progress
on
this
project
in
the
last
couple
of
months,
because
October
28th
is
our
launch
date
for
Z
cash
and
it's
coming
up
fast,
like
five
weeks
or
something
from
now,
so
hopefully
we'll
make
more
progress
on
the
project,
alchemy
and
the
other
two
after
that,
and
in
the
meantime,
other
people
have
been
making
some
progress
contributing
to
it.
So
you
should,
if
you
find
this
interesting
at
all.