Hide your nuts!
...with Cashu - an eCash system for the Bitcoin Lightning network
- 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?
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_
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_
I return your blinded secret with mints signature
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
I return your blinded secret with mints signature
-
*
=
C
C_
8
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
Here is my blinded secret and payment hash
| PUB | PRIV | Amount |
|---|---|---|
| 123abc | afd890 | 1 |
| ... | ... | ... |
| 456def | 876acb | 8 |
k
I return your blinded secret with mints signature
C
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
Here is my blinded secret and payment hash
| PUB | PRIV | Amount |
|---|---|---|
| 123abc | afd890 | 1 |
| ... | ... | ... |
| 456def | 876acb | 8 |
k
I return your blinded secret with mints signature
C
*
==
How does Cashu work?
How does Cashu work?
How does Cashu work?
- Wallets use the mints LN node
- No balance, no ID, no UTXOs
How does Cashu work?
- Wallets use the mints LN node
- No balance, no ID, no UTXOs
- Mints inerop over LN
- Private ecash transactions
Why Cashu?
- LN self custody is "hard"
- LN privacy is complicated
- User data ownership
- Bearer tokens UX
Cashu usage
Mints
Wallets
cashu nutshell
cashu nutshell
feni
feni
redeem
Nutstash usage
Nutstash usage
Nutstash usage
Connect with mints
Nutstash usage
Connect with mints
Use Wallet
Nutstash usage
Send
Receive
Mint
Pay LN invoice
Nutstash usage
Swap between mints
Integrate with nostr
Nutstash usage
Other usages?
We've seen...
- Private LN payments using custodians
- Sending bearer asset tokens via DMs
Other usages?
We've seen...
- Private LN payments using custodians
- Sending bearer asset tokens via DMs
Yet to come....
- Paid REST requests (X-Cashu)
- Cashu nostr relays
- ...
Cashu development
We're not there yet...
Join us!
- Telegram: https://t.me/CashuBTC
- Docs: https://docs.cashu.space
- These slides: https://lconf.gandlaf.com
- Token backups
- Fractional reserve rug-pulling
- Making it easy for developers and user: Simple protocol, great libraries & easy to run software
Cashu development
Join us!
- Telegram: https://t.me/CashuBTC
- Docs: https://docs.cashu.space
- These slides: https://lconf.gandlaf.com
