Hide your nuts!

@gandlaf21

...with Cashu - an eCash system for the Bitcoin Lightning network

@gandlaf21

  • Open source dev
  • Cashu: eCash protocol by @callebtc
  • Nutstash: Cashu wallet

ECash

  • Heard about it?
  • Understand it?
  • Used it?

What is eCash?

  • ECash =/= Bitcoin
  • 1982 by David Chaum
  • Privacy respecting, electronic value transmission protocol
  • Using blind signatures

How does eCash work?

(ELI5)

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

verysecret..xyz

carbon envelope

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

carbon envelope

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

carbon envelope

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

  • The mint has never seen our secret                

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

  • The mint has never seen our secret
  • The mint can verify the secret validity/amount because of the stamp

How does eCash work?

(ELI5)

I want to mint 5$ worth of eCash

Mint Request

Mint Request Response

Ok, send me 5$ and a secret (inside carbon envelope)

Mint

Here is my blinded secret and 5$

Mint Response

I return your blinded secret with mints signature

  • The mint has never seen our secret
  • The mint can verify the secret validity/amount because of the stamp
  • Bearer token

How does Cashu work?

Mint Request

Mint Request Response

Mint

Mint Response

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

B_

Y

+

r

G

=

Y: secret

r: blinding factor

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

B_

Y

r

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

B_

Y

r

Here is my blinded secret and payment hash

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

B_

Y

r

Here is my blinded secret and payment hash

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

B_

Y

r

Here is my blinded secret and payment hash

PUB PRIV Amount
123abc afd890 1
... ... ...
456def 876acb 8

K

k

How does Cashu work?

I want to mint 8 sats worth of eCash

Mint Request

Mint Request Response

Mint

Mint Response

Ok, pay LN-invoice and send blinded secret

await payment...

Y

r

Here is my blinded secret and payment hash

PUB PRIV Amount
123abc afd890 1
... ... ...
456def 876acb 8

K

k

*

=

C_

B_

8

How does Cashu work?