Cross-Platform Mobile Application for the Cothority Sacha Kozma - - PowerPoint PPT Presentation

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Dec 07, 2023 10 likes •424 views

Cross-Platform Mobile Application for the Cothority Sacha Kozma June 12, 2018 Decentralized and Distributed Systems lab, EPFL Responsible Prof. Bryan Ford Supervisor Linus Gasser 1 5 Conclusion 7 Demo 6 Drawback Presentation BeerCoin

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Cross-Platform Mobile Application for the Cothority

Sacha Kozma June 12, 2018

Decentralized and Distributed Systems lab, EPFL Responsible Prof. Bryan Ford Supervisor Linus Gasser

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1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

1

SLIDE 3

What is CPMAC ?

iOS and Android application used for Cothority.

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What is CPMAC ?

iOS and Android application used for Cothority.

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SLIDE 5

What is CPMAC ?

iOS and Android application used for Cothority. Currently supported applications:

Status
Proof-of-Personhood
Cisc Identity SkipChain

Built on top of NativeScript.

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SLIDE 6

1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

3

SLIDE 7

Improvements

Work has been done on several points :

PoP-Parties
Attendees support
Confjguration sharing
Usability
User Interface
Process simplifjcations
New feature : BeerCoin

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SLIDE 8

1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

5

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Proof-of-Personhood

Organizers agree on the party details

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Proof-of-Personhood

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Proof-of-Personhood

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SLIDE 12

Proof-of-Personhood

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Proof-of-Personhood

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Proof-of-Personhood

At the end of the party, the conodes generate : + + collective signature = Final statement And each attendee can generate : Final statement + attendee’s key pair = PoP-Token

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1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

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Party description sharing

Until now, CPMAC used PasteBin to share the party description to the other organizers. This approch has drawbacks !

Depends on third-party services
Party description is publicly available

Instead, adapt Cothority to use conodes !

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Party description sharing

Until now, CPMAC used PasteBin to share the party description to the other organizers. This approch has drawbacks !

Depends on third-party services
Party description is publicly available

Instead, adapt Cothority to use conodes !

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Party description sharing

Until now, CPMAC used PasteBin to share the party description to the other organizers. This approch has drawbacks !

Depends on third-party services
Party description is publicly available

Instead, adapt Cothority to use conodes !

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Party description sharing with PasteBin

Organizer 1 PasteBin Organizer 2 1) Upload party description 2) Send PasteBin link with QR Code 3) Fetch party description

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Party description sharing with PasteBin

Organizer 1 PasteBin Organizer 2 1) Upload party description 2) Send PasteBin link with QR Code 3) Fetch party description

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Party description sharing with PasteBin

Organizer 1 PasteBin Organizer 2 1) Upload party description 2) Send PasteBin link with QR Code 3) Fetch party description

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Party description sharing with PasteBin

Organizer 1 PasteBin Organizer 2 1) Upload party description 2) Send PasteBin link with QR Code 3) Fetch party description

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Party description sharing with conodes

Organizer 1 Conode 1 Organizer 2 Conode 2 1) Upload description 2) Description is propagated 3) Fetch party proposal

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Party description sharing with conodes

Organizer 1 Conode 1 Organizer 2 Conode 2 1) Upload description 2) Description is propagated 3) Fetch party proposal

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Party description sharing with conodes

Organizer 1 Conode 1 Organizer 2 Conode 2 1) Upload description 2) Description is propagated 3) Fetch party proposal

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Party description sharing with conodes

Organizer 1 Conode 1 Organizer 2 Conode 2 1) Upload description 2) Description is propagated 3) Fetch party proposal

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SLIDE 27

1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

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Linkable Ring Signatures

Ring Signatures:

Allow a user to sign on behalf of a group
One can verify that someone from this group effectively

signed the data

But he cannot know which member precisely

Linkable Ring Signatures:

Same as ring signatures
But a linkage scope can be defjned, and the verifjcation

process will then yield a tag, which is unique to the signer under that scope

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SLIDE 29

Linkable Ring Signatures

Ring Signatures:

Allow a user to sign on behalf of a group
One can verify that someone from this group effectively

signed the data

But he cannot know which member precisely

Linkable Ring Signatures:

Same as ring signatures
But a linkage scope can be defjned, and the verifjcation

process will then yield a tag, which is unique to the signer under that scope

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SLIDE 30

1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

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BeerCoin

A long-running joke at DEDIS ! BeerCoins are distributed in a group and each day/month/week they can have a beer. In CPMAC, it’s called a Bar It allows showing a simple example of what could be done with the current primitives implemented in CPMAC. Each member of the group gets a PoP-Token and the Bar uses linkable ring signatures to verify it.

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SLIDE 32

BeerCoin

A long-running joke at DEDIS ! BeerCoins are distributed in a group and each day/month/week they can have a beer. In CPMAC, it’s called a Bar It allows showing a simple example of what could be done with the current primitives implemented in CPMAC. Each member of the group gets a PoP-Token and the Bar uses linkable ring signatures to verify it.

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Linkable Ring Signatures for BeerCoin

In the case of BeerCoin, the scope should be unique for each Bar and each period : scope = bar_namefrequencyyearmonthday frequency ∈ {daily, weekly, monthly}

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Linkable Ring Signatures: Client verification

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1

CPMAC Presentation

2

Improvements

3

Proof-of-Personhood Presentation PoP in CPMAC

4

Linkable Ring Signatures

5

BeerCoin Presentation Drawback

6

Demo

7

Conclusion

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Drawbacks

One major drawback comes from the association of QR Code with linkable ring signatures :

Length of signatures is proportional to the number of

member in the group

But QR Code has fjxed capacity

Actually, CPMAC could handle a maximum of 90 members per group.

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Drawbacks

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Demo time !

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Conclusion

CPMAC is increasingly becoming a large public app. The primitives currently added allows some interesting applications :

Voting system
Online chat
Authentication
and many more

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