# @unirep/crypto

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### 🛠 Install

#### npm or yarn

Install the `@unirep/crypto` package with npm:

```bash
npm i @unirep/crypto
```

or yarn:

```bash
yarn add @unirep/crypto
```

### 📔 Usage

#### ZkIdentity

**Generate a random ZkIdentity**

```typescript
import { ZkIdentity } from '@unirep/crypto'
const identity = new ZkIdentity()
```

**Generate identity commitment**

```typescript
const commitment = identity.genIdentityCommitment()
```

**Get identity nullifier**

```typescript
const commitment = identity.identityNullifier
```

**get identity trapdoor**

```typescript
const commitment = identity.trapdoor
```

**Serialize/ unserialize identity**

```typescript
import { Strategy } from '@unirep/crypto'
// serialize identity
const serializedIdentity = identity.serializeIdentity()
// unserialize identity
const unserializedIdentity = new ZkIdentity(
    Strategy.SERIALIZED,
    serializedIdentity
)
```

#### IncrementalMerkleTree

**Create an IncrementalMerkleTree**

```typescript
import { IncrementalMerkleTree } from '@unirep/crypto'

const depth = 4
// initialize incremental merkle tree with depth 4
const tree = new IncrementalMerkleTree(depth)
```

**Get tree root**

**Insert leaf**

```typescript
const leaf = 1
tree.insert(leaf)
```

**Generate merkle proof**

```typescript
const index = 0
const proof = tree.createProof(index)
```

**Verify merkle proof**

```typescript
const isValid = tree.verifyProof(proof)
```

#### SparseMerkleTree

**Create a SparseMerkleTree**

```typescript
import { SparseMerkleTree } from '@unirep/crypto'

const depth = 4
// initialize incremental merkle tree with depth 4
const zeroHash = 0
// initialize sparse merkle tree with depth 4 and zeroHash 0
const tree = new SparseMerkleTree(
    depth, 
    zeroHash
)
```

**Get tree root**

**Update leaf**

```typescript
const leafKey = BigInt(3)
const leafValue = BigInt(4)
tree.update(leafKey, leafValue)
```

**Generate merkle proof**

```typescript
const leafKey = Bigint(1)
const proof = tree.createProof(leafKey)
```

**Verify merkle proof**

```typescript
const isValid = tree.verifyProof(proof)
```

#### Crypto utils

**genRandomSalt**

```typescript
import { genRandomSalt } from '@unirep/crypto'

// generate random BigInt
const salt = genRandomSalt()
```

**hash5**

```typescript
import { hash5 } from '@unirep/crypto'

// poseidon hash 5 BigInt elements
const values = [
    genRandomSalt(),
    genRandomSalt(),
    genRandomSalt(),
    genRandomSalt(),
    genRandomSalt(),
]
const hash5Value = hash5(values)
```

**hashOne**

```typescript
import { hashOne } from '@unirep/crypto'

// poseidon hash 1 BigInt elements
const value = genRandomSalt()
const hashOneValue = hashOne(value)
```

**hashLeftRight**

```typescript
import { hashLeftRight } from '@unirep/crypto'

// poseidon hash 2 BigInt elements
const leftValue = genRandomSalt()
const rightValue = genRandomSalt()
const hash = hashLeftRight(leftValue, rightValue)
```

**stringifyBigInts/unstringifyBigInts**

```typescript
const values = {
    input1: genRandomSalt(),
    input2: genRandomSalt(),
    input3: genRandomSalt(),
}
// stringify BigInt elements with stringifyBigInts function
const stringifiedValues = stringifyBigInts(values)
// it can be recoverd by unstringifyBigInts function
const unstringifiedValues = unstringifyBigInts(stringifiedValues)
```