> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Blob.toCommitment

> Compute 48-byte KZG commitment for blob

<Card title="Try it Live" icon="play" href="https://playground.tevm.sh?example=primitives/blob.ts">
  Run Blob examples in the interactive playground
</Card>

<Tabs>
  <Tab title="Standard API">
    ```typescript theme={null}
    import { Kzg, Blob } from 'tevm';

    const blob = Blob.fromData(data);
    const commitment = Kzg.Commitment(blob);

    console.log(commitment.length); // 48
    console.log(Blob.Commitment.isValid(commitment)); // true
    ```

    **Note:** Requires c-kzg-4844 library integration (coming soon).
  </Tab>

  <Tab title="Factory API">
    ## `ToCommitment({ blobToKzgCommitment })(blob): Commitment`

    Tree-shakeable factory pattern with explicit KZG dependency.

    **Dependencies:**

    * `blobToKzgCommitment: (blob: Uint8Array) => Uint8Array` - KZG commitment function from c-kzg-4844

    **Example:**

    ```typescript theme={null}
    import { Kzg } from 'tevm'
    import { blobToKzgCommitment } from 'c-kzg'

    const Commitment = Kzg.CommitmentFactory({ blobToKzgCommitment })
    const commitment = Commitment(blob)
    ```

    **Bundle size:** KZG crypto only included if you import it explicitly.

    **Note:** Requires c-kzg-4844 library integration (coming soon).
  </Tab>
</Tabs>

## KZG Commitment Scheme

KZG commitments use polynomial commitment scheme over BLS12-381 curve:

1. **Blob as Polynomial** - 4096 field elements become polynomial coefficients
2. **Commitment** - Evaluate polynomial at secret point (from trusted setup)
3. **Binding** - Computationally infeasible to find different blob with same commitment

### Security Properties

```typescript theme={null}
import { Kzg, Blob } from 'tevm';

// Different data = different commitments
const blob1 = Blob.fromData(data1);
const blob2 = Blob.fromData(data2);

const commitment1 = Kzg.Commitment(blob1);
const commitment2 = Kzg.Commitment(blob2);

// Commitments differ (binding property)
console.log(Blob.equals(commitment1, commitment2)); // false

// Cannot forge commitment for different data
const proof1 = Kzg.Proof(blob1);
console.log(Kzg.verify(blob1, commitment1, proof1)); // true
console.log(Kzg.verify(blob2, commitment1, proof1)); // false (wrong blob)
```

## Commitment Utilities

### Blob.Commitment Namespace

```typescript theme={null}
import { Kzg, Blob } from 'tevm';

const commitment = Kzg.Commitment(blob);

// Validate commitment size
console.log(Blob.Commitment.isValid(commitment)); // true

// Convert to versioned hash
const versionedHash = Blob.toVersionedHash(commitment);
console.log(versionedHash[0]); // 0x01 (version byte)
```

## See Also

* [toProof](./toProof) - Generate KZG proof
* [verify](./verify) - Verify commitment and proof
* [toVersionedHash](./toVersionedHash) - Compute versioned hash
* [KZG](/primitives/blob/kzg) - KZG commitment scheme details