foreign
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crypto we're a VC funds
um
crypto native uh anyways
um Okay so
what I've been talking about today is uh
not about your dollar proofs and let me
open by a question raise your hand if
you think it's your knowledge solve all
the Privacy problems in the blockchain
space
I see one hand
let's see two three all right well if
you didn't raise your hands maybe um
well maybe you know better than I do but
I don't think zero dollars off all the
Privacy problems so let me explain why
so
um let's think about blockchains so what
are blockchains and computation right uh
blockchains applications uh everything
is a computation on the blockchain right
so ethereum is a public State machine
that's replicated uh if you have some
consensus mechanism
and so what is it what is the same
machine it's the same machine is
something that uh keeps a state and has
a transition function and transition
stays through transition function right
and more computers same machines
blockchains and smart contracts right so
everything on ethereum all the smart
contracts are State machines
okay what if we want to do the same
machine transitions uh with privacy well
let's try to use your knowledge how are
you going to as you go to sleep machines
your knowledge well we're going to
execute the off chain and only prove the
execution that is correct on chain right
so I'm not going to show you the details
here but more or less is going to look
like this picture where every single
States you know it's a different color
and your do knowledge update is going to
uh essentially link one color to another
color right so here on chain will have
three different states
as opposed to the user want to interact
with the state machine and uh they each
independently enjoy a different proof
right thinking state two to some state
three
now if
one proof is processed on chain
let's say the the live one the blue one
here what happens is that
the second transaction of this of the
second user is now invalid right because
it's
the proof um is going from
the same like state two but now you need
to link to stage three right so so
that's the problem with executing
General State machines in general
knowledge blockchain you range of race
conditions
okay so this problem is actually been
observed over the years in many
different ways but basically
um you know the the store is at either
you do a transparent engine computation
which you know that we do on ethereum so
you have no privacy but you have the you
know benefit of a share state that
everybody can have access to
or on the other hand you have a zero
knowledge of chain execution uh and you
kind of have the flipped uh you know
uh benefits and and kind of downsides
which is that you have private inputs
but to State that's not shared between
anyone okay so uh we're basically
someone like us with you know these two
properties so we can't really get both
and my talk is about how to get both
properties and I call that
um a confidential share state so how do
we get confidential share states on the
blockchain
and the answer is fully homomorphic
encryption or fhe for short
okay so what is home of encryption
um this is you know brief intro to
cryptography so
um so this thing is here is kind of
commutative diagram okay so suppose
there's a message
and fix a circuit see here we can
compute the circuit on a message to get
C of M so that's this error over here
okay
um at which this scheme allows you to
kind of do this thing but with three
different steps okay uh and so first
let's take our message instead of
computing the function I'm going to
encrypt it okay so everything that's
done here is encrypted you can now see
what's inside right so uh you know this
is what kind of go through in your TLS
channels and stuff like that right you
first encrypt it and then you kind of
run this evaluation function which takes
in the circuit right and this uh stepper
text
to get another set for text okay
um we'll have you down here well I
haven't really done anything useful
right but let's actually try to decrypt
this thing again right uh if a fishy
skin allows you to essentially
um so if you decrypt this and you know
and there's things that it's uh you know
it actually works it means that you
actually get back to the resultant
computation okay so what have we done
here instead of doing computation in the
clear
we can first encrypt do the computation
and then decrypt Okay so so this thing
is like really really sick right because
um it allows you to do computational
encrypted data it's like you know the
Holy Grail of you know Computing uh and
privacy right
um
so you know this thing has been
discussed ever since like the 80s
um but like you know recently we like
only within the past about 15 years do
we know constructions of this thing okay
so there's still a single point of
failure here which is the decryption key
right so that anyone holds a decryption
key can get the data so the idea is
we're going to like move everything
Unchained to be encrypted and stuff
right so but we don't want a single
person to be able to decrypt so what do
we do we're going to add
um thresholds cryptography we're going
to SQL share the decryption key to every
single validator okay so now I'm gonna
have to guarantee that you can only
reconstruct what's inside if
um
if k out of the N validators say so okay
all right so all right so what can we do
with that uh you know with such a
virtual Effigy scheme uh it turns out we
can basically uh you know do
confidential same machine replication on
chain
and to release any information uh you
know that we want to the public
so let me kind of wrap up by telling you
about the work of Pesca uh so Pesca it's
uh well short for privacy enhancing
smart contract architecture which is
kind of a blueprint to unify the three
types of computation right so we have
transparent unchain computation zero
knowledge option computation and this on
chain replicated computation computation
is a framework that I try to unite the
three things you know putting the three
together
um so very briefly on what kind of what
the challenge is here so the challenge
is that if you want to make this in
Practical uh you have to really really
think about efficiency as it so it turns
out FH is really really slow and uh is
way slower than ZK even so you want to
push computation to zero knowledge as
much as possible while doing you know
the bare minimum amount of like shared
computation in fhg okay and uh I'm going
to kind of connect the two components
using virtual decryption so it's going
to look at look like this where on the
left hand side we'll have some type of
like DK shooter tool which is really
standards we're going to also use zero
dollars to kind of
encode inputs into this apigee
computation module on chain and then
we're going to decrypt stuff and then
put it back into the you know through
the pool
um so this is actually inspired by the
penumbra State model I encourage you to
kind of look it up it's it's actually
one of the
cooler projects that's you know being
implemented right now that have that's a
private X okay anyways um and in the
work we also extend this to uh to some
Publications uh one of which is uh
essentially a dark pool a privacy
preserving custom function Market maker
and the other one is uh first first
price privacy preserve auction
okay so let me in by a short conclusion
which is uh you know what are the three
points I talk about today privacy is
you know privacy it's really important
in blockchain space and zero knowledge
is not a full solution
and to get confidential share States we
need something that's fancier and in
this talk I presented one option using
apigee
and encourage you to go check out the
work of best gun and the link to the
paper is in this QR code anyone that
they didn't raise their hands everybody
understood that
already when stuck with way after the
talk thank you so much wait once again