> For the complete documentation index, see [llms.txt](https://gothamcash.gitbook.io/bindowscash/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gothamcash.gitbook.io/bindowscash/deposit-the-fixed-amount-with-a-commitment-hash.md).

# Deposit the fixed amount with a commitment hash

Let's dive into the deposit process. To deposit funds into BindowsCash, you must send **a fixed amount of BNB** to the contract, along with your unique **commitment hash**. This commitment acts as a cryptographic placeholder for your deposit and will later be used to anonymously prove ownership when you withdraw.

{% hint style="info" %}
It's like getting a cloakroom ticket for a jacket that you leave in a nightclub, and then get back at the end of the night with that same ticket: without it, you won't be able to get your jacket back.
{% endhint %}

#### What is a commitment?

A commitment is a hash generated from two secret random values:

* A **nullifier** (used to prevent double spending)
* A **secret** (used to add entropy)

Both values are combined and hashed (using `keccak256`and `sha256`) to produce the commitment. This commitment is **what gets stored on-chain** — never the secret or nullifier themselves.

Example:

```
rand = ethers.hexlify(ethers.randomBytes(32));
commitment = keccak256(rand)
```

You’ll receive a **note** (e.g. `bindowscash-bnb-0.1:0xabc...-0xcontract`) that encodes all these informations. Keep this note safe — you’ll need it to withdraw your funds.

***

#### Deposit process:

1. Choose your deposit amount (e.g. 0.1 BNB, 1 BNB, or 10 BNB).
2. Use the BindowsCash dApp to generate a note and the commitment hash.
3. Send the fixed amount along with your commitment via the deposit interface.
4. Your deposit will be registered on-chain, and you'll see a confirmation.

The dApp will automatically calculate the correct total to send. You don't need to worry about gas math — just follow the interface.

***

#### Important:

* **Only fixed amounts** are accepted. If you send any other amount, the transaction will revert.
* Make sure to **save your note** immediately after deposit. If you lose it, you will **not be able to withdraw** your funds later.
* Deposits are anonymous: no address or identity is stored on-chain, only the commitment.