Skip to content
Cashu (Ecash on Lightning)
Cashu is an ecash system that uses Lightning for funding.
It can provide strong privacy with clear trust trade-offs.
Education only. No financial advice.
Cashu can be useful for small, private transfers.
It also introduces a trusted mint.
Three key points
Cashu is a privacy tool, not a base layer.
It is best used with clear limits.
Tokens can move person to person
A bearer token is controlled by whoever holds it.
Passing the token passes the claim.
Less linkability between payments
The mint signs tokens without seeing their final form.
This can reduce tracing by the issuer.
The mint can fail or cheat
Users trust the mint to redeem tokens later.
This is not the same as self-custody.
What is ecash?
Ecash is digital cash-like tokens.
Tokens can be spent without revealing a payment history.
Ecash aims to feel like cash.
Cash means the payer does not need an account with the receiver.
Ecash uses cryptography to prevent double spending.
Double spending means using the same token twice.
Cashu is one ecash design.
It uses a mint to issue and redeem tokens.
The tokens represent bitcoin value.
They are typically funded and redeemed via Lightning.
What is a mint?
A mint is an issuer and redeemer of ecash tokens.
It holds bitcoin reserves and signs token promises.
Minting tokens
You pay the mint, usually over Lightning.
The mint returns signed ecash tokens.
Redeeming tokens
You return tokens to the mint.
The mint pays out, usually over Lightning.
Backing and solvency
The mint should hold enough bitcoin to redeem tokens.
If it does not, users can be harmed.
Privacy properties
Privacy is about what others can learn about you.
Cashu can reduce linkability between actions.
Cashu uses blinded signatures.
A blinded signature lets the mint sign a message without seeing it.
This can hide which specific tokens you later spend.
The mint may still see your deposit and your withdrawal times.
Privacy is not absolute.
Network metadata can still leak information.
Operational choices matter.
For example, how you connect and when you redeem can affect privacy.
Trust model
Trust model means who you must rely on.
Cashu requires trust in a mint operator.
Who controls the reserves
The mint controls the reserve bitcoin.
Users hold tokens that represent a claim.
Service can go offline
If the mint is offline, redemption may be delayed.
Tokens may be hard to use outside the mint ecosystem.
Mint can misbehave
A dishonest mint can refuse redemption.
A failed mint can lose keys and break redemption.
Comparison table
This table compares the layers in plain terms.
It focuses on security, privacy, and trust.
| Layer | What it is | Trust needed | Privacy level | Best for |
|---|---|---|---|---|
| Mainchain Layer 1 |
Public ledger with global verification. Settlement is recorded on-chain. |
Minimal trust in people. You rely on rules and your own verification. |
Limited by default. Data is public, but addresses are not names. |
High-value settlement. Long-term ownership records. |
| Lightning Layer 2 |
Channel network for fast payments. Most updates are off-chain. |
Trust is limited. You still rely on Layer 1 enforcement for disputes. |
Better than on-chain in many cases. Some routing metadata can still leak. |
Frequent payments. Quick transfers and low on-chain footprint. |
| Cashu Ecash |
Bearer tokens issued by a mint. Tokens move over messages or apps. |
Strong trust in the mint. You rely on redemption and honest operation. |
Can be strong against linkability by the mint. Network metadata can still exist. |
Small private transfers. Temporary balances with clear risk limits. |
When to use which layer
This is a simple decision guide.
It is not a recommendation for any product.
Use Mainchain for settlement
Choose Layer 1 when you need strong finality.
It is best for important ownership records.
Use Lightning for speed
Choose Lightning for frequent payments.
It works well when you can keep channels open.
Use Cashu for private tokens
Choose Cashu when privacy is a priority for small balances.
Keep the mint trust in mind.
Trust and risk explained simply
Risk means what can go wrong.
Trust means who can cause that harm.
With Mainchain self-custody, you hold keys.
Keys are secrets that control spending.
Risk comes from losing keys or making mistakes.
No operator can block redemption because there is no operator.
With Cashu, you trust the mint to redeem tokens.
If the mint fails, tokens may become worthless.
A careful approach is to limit exposure.
Use smaller balances and redeem regularly if needed.
How the layers fit together
Cashu is a higher layer that often uses Lightning.
Lightning and Cashu can settle back to Layer 1.
Think of layers as different tools.
They share the same base asset, but different trust assumptions.
Trust concentrates in the mint.
Liquidity and online availability matter.
Capacity is limited to keep verification broad.
FAQ
These answers are simple and honest.
They focus on how Cashu works.
Is Cashu the same as Bitcoin?
No. Cashu is a system built on top of Bitcoin and Lightning.
It uses a mint that issues tokens.
Can the mint see what I spend?
Cashu can reduce linkability between minting and spending.
The mint may still see deposits, withdrawals, and network timing.
What is the biggest risk?
The biggest risk is mint failure or refusal to redeem.
This is why users should understand the trust model.
Review the full system
Start from Layer 1, then add Lightning, then add Cashu.
This order keeps concepts clean.