Digital Asset Custody 

Using MPC

Technology Advisory Committee

February 2020
2

Discussion Points

The Challenge

• Security v. Liquidity

• An impractical solution

The Building Blocks

• Multi-Party Computation

• Zero Knowledge Proof

• Diffie-Hellman

What this Means for Custody

• Distributed, mathematical resolution

• Trade-off between security and liquidity evaporates
3

While blockchains enable a connected decentralized economy,

private keys dictate a disconnected centralized infrastructure.

Breaking the paradigm requires expertise 

in security and cryptography.

The Challenge - Security v. Liquidity

Existing Solutions

Liquidity Security

Single-Sig

Hardware

Cold

Single Key

Multi-sig

Sharding

Software

Hot
4

• The blockchain itself is based on math

• An elegant solution to the challenge of storing 

and sharing information in a decentralized 

model.

• Protecting it with a combination of human labor 

or hardware reduces the benefits of that 

ecosystem. 

• The safest and most practical way to protect a 

mathematical protocol is with math itself

The Challenge – An impractical solution

Signing an EDDSA transaction for a specific pub address with a private key

The community then verifies you must have had the correct key

Generate a pub address with a private key

EdDSA Curve Calculations
5

The Building Blocks – MPC 

The ability of multiple parties 

to jointly perform

mathematical computations 

without any party revealing 

its secret to the others. 
6

The Building Blocks – Zero Knowledge Proof 

Method by which one party (the prover) can demonstrate to another 

party (the verifier) that they know a value x, without conveying any 

information apart from the fact that they know the value x.

Alice Bob

• Alice wants to prove to Bob – who is colorblind – that a red and green ball are truly different.

• She asks him to hide one behind his back and show her the other.

• He then takes both back – either swaps them or doesn’t – and shows her one a second time.

• Alice confirms to Bob whether he swapped them or not.
7

The Building Blocks – Diffie Hellman 

Publicly agree on two numbers

p = prime (29)

g = generator (4)

Randomly generate 2 local values. 

Calculate the Public Address | shared*g^local Mod p

Alice Bob

Exchange the result

Calculate a public variant | g^local Mod p

12 10

(4 ^ 12) Mod 29 = 20 (4 ^ 10) Mod 29 = 23

20

23

(20 * 23) Mod 29 = 25 (23 * 20) Mod 29 = 25

Jointly calculated public Key = 25 Implicit Key (⍺) = 12 + 10 = 22

L1 L2

Validation = 4 ^ (22) Mod 29 = 25
8

Can multiple parties work together to solve signature equations without

ever creating a key to begin with – nor ever exposing any critical information 

to one another?

What it means – is there another way? 

Collaboratively calculating a public address

Collaboratively signing

Collaboratively calculating a hash

Yes

Yes

Yes
9

What this means for custody 

Secure

○ Eliminates any single point of failure

○ Local variables can be constantly rotated to avoid compromise

Connected

○ Empowers instant access to all digital assets

Flexible

○ Rules can define when and how local variables are used

Blockchain agnostic

○ Security no longer the responsibility of the DLT

The trade-off between security and liquidity evaporates
Q&A

Itay Malinger, Co-Founder and CEO

itay@curv.co

www.curv.co