Digital Payment System Using X.509

Supervisor: Ken Taylor (CSIRO)

Student: Tim Mathas

What makes up a single point of control payment system?

Redeemer Creator

Transaction Database

Buyer Seller

Digital Payment System Using X.509

What makes up a decentralised payment system?

Registrar

Token Owner

Digital Payment System Using X.509

Redeemer

Exchanger

Creator

Assigner

Decentralised payment system

Payment system properties

Authentication

Integrity

Prevention of double spending

Single ownership

Digital Payment System With X.509

What is X.509?

Establishes trust for web sites

Certificate Issuer: A Subject: B

Certificate Issuer: B Subject: D

Certificate Issuer: B Subject: C

Certificate Issuer: B Subject: E

endorses 1

3 4 2

Digital Payment System Using X.509

What is X.509?

Contents

Certificate Data

Subject Information

Issuer Information

Hash algorithm

Extensions

Certificate Signature Algorithm

Certificate Signature

Digital Payment System Using X.509

What is X.509?

Contents Digital Signature Creation

Certificate Data

Subject Information

Issuer Information

Hash algorithm

Extensions

Certificate Signature Algorithm

Certificate Signature

H

E

Issuer’s

private

key

Issuer

Unsigned certificate- Contents: <any data>, user’s public key

Hash of unsigned certificate

Signed certificate- Recipient can verify signature using Issuer’s public key

Digital Payment System Using X.509

What is X.509?

Creation Verification

H

E

Issuer’s

private

key

Issuer

Unsigned certificate- Contents: <any data>, user’s public key

Hash of unsigned certificate

Signed certificate- Recipient can verify signature using Issuer’s public key

H

Issuer’s

public key Hash of unsigned certificate

Signed certificate- Recipient can verify signature using Issuer’s public key

D

Digital Payment System Using X.509

How good a fit is X.509 for payment systems?

Authentication

Integrity

Prevention of double spending

Single ownership

Digital Payment System Using X.509

How good a fit is X.509 for payments systems?

Authentication

Integrity

Prevention of double spending

Single ownership

Digital Payment System Using X.509

First attempt

Certificate Issuer: CA Subject: CA

Certificate Issuer: CA Subject: Ian

a

d

b

Issuer Certificates

Certificate

Token

Issuer: Ian #1001 Subject: Simon

Certificate

Certificate

c

Issuer: CA Subject: Simon

e

Token Creation Certificate

Issuer: Ian Subject: Ian #1001 Token Type: IanToken Token Qty: 200 … other information …

Token Chain Certificates

Digital Payment System Using X.509

Registrar: Double spending example

Certificate Issuer: Alex Subject: Alex

Certificate

Token

Issuer: Alex Subject: Alex #1001 Token Type: AlToken Token Qty: 200 … other information …

Issuer: Alex #1001 Subject: Bob

a

b

c d

Certificate

Id

Certificate

Id

Issuer: Alex #1001 Subject: Claire

Alex attempting to issue the same certificate to Bob and Claire

Digital Payment System Using X.509

Problem with first attempt

Certificate Issuer: Alex Subject: Alex

Certificate

Token

Certificate

Token

Issuer: Alex Subject: Alex #1001 Token Type: AlToken Token Qty: 200 … other information …

Issuer: Alex Subject: Alex #1002 Token Type: AlToken Token Qty: 400 … other information …

Issuer: Alex #1002 Subject: Bob

Issuer: Alex #1001 Subject: Bob

a

c b

d e

f

Certificate

Certificate

Certificate Issuer: Bob Subject: Claire

Chain: C1

Chain: C2

Digital Payment System With X.509

Second attempt

Certificate Issuer: Alex Subject: Alex

Certificate

Token

Certificate

Token

Issuer: Alex Subject: Alex #1001 Token Type: AlToken Token Qty: 200 … other information …

Issuer: Alex Subject: Alex #1002 Token Type: AlToken Token Qty: 400 … other information …

Issuer: Alex #1001 Subject: Bob Id: <Alex, Alex #1001>

a

c b

d e

f

Certificate

Id

Certificate

Id

Issuer: Bob Subject: Claire Id: <Alex #1001 pub key>

Chain: C1

Chain: C2

Certificate

Id

Issuer: Alex #1002 Subject: Bob Id: <Alex #1002 pub key>

Digital Payment System With X.509

Final attempt

Certificate Issuer: Alex Subject: Alex

Certificate

Token

Certificate

Token

Issuer: Alex Subject: Alex #1001 Token Type: AlToken Token Qty: 200 … other information …

Issuer: Alex Subject: Alex #1002 Token Type: AlToken Token Qty: 400 … other information …

Issuer: Alex #1001 Subject: Bob Id: <Alex, Alex #1001> PositionInChain: 1

a

c b

d e

f

Certificate

Id

Certificate

Id

Issuer: Bob Subject: Claire Id: <Alex #1001 pub key> PositionInChain: 2

Chain: C1

Chain: C2

Certificate

Id

Issuer: Alex #1002 Subject: Bob Id: <Alex #1002 pub key> PositionInChain: 1

Digital Payment System With X.509

How good a fit is our modified X.509 for payment systems?

Authentication

Integrity

Prevention of double spending

Single ownership

Digital Payment System With X.509

How good a fit is our modified X.509 for payment systems?

Authentication

Integrity

Prevention of double spending

Single ownership

Digital Payment System With X.509