# Ephemeral Deposits
The ephemeral deposit scheme was designed to give the ability to deposit to a zk-account from the smart contracts (e.g. bridges). The idea is to temporary give control over the deposited funds to some EOA, which can then make a regular permittable deposit.
Such an EOA is an ad-hoc generated account derived from the zk-account spending key. So the library controls ephemeral private keys and has full access over the funds on the ephemeral addresses
Since deposits to a single zkBob account can be made from different smart contract wallets, reusing the same ephemeral EOA address is not a good idea, as it can be used to link together independent deposits. A better option is to use a newly generated EOA address for each new deposit.
{% hint style="warning" %}
Using ephemeral deposit scheme is an early developed feature. At now the [direct deposits](/implementation/client-library-sdk/full-mode-operations/direct-deposits.md) are more suitable to process external deposits
{% endhint %}
## Sending Ephemeral Deposits
To use an ephemeral deposit you should send funds to the ephemeral address first. The address must have a sufficient balance to process the deposit and cover the relayer fee.
```typescript
async depositEphemeral(
amountGwei: bigint,
ephemeralIndex: number,
relayerFee?: RelayerFee,
): Promise
```
### Parameters
`amountGwei` - token amount to deposit into an account (in pool dimension).
`ephemeralIndex` - an index of the ephemeral address.
`relayerFee` - a raw [relayer fee object](/implementation/client-library-sdk/common-types.md#relayer-raw-fee) which will be used to estimate the total transaction fee (will requested under the hood when undefined).
### Returns
`Promise` returns `jobId` returned by relayer which can be use to monitor the transaction.
### Example
```typescript
const myAddress = await zkClient.directDeposit(90000000000n, 0);
console.log(`Ephemeral deposit sent to the relayer (job ID = ${jobId})`)
// output: Ephemeral deposit sent to the relayer (job ID = 4736)
```
## Getting the First Non-Used Ephemeral Address Index
Scanning over the ephemeral addresses pool to find the first address which was not in use. The address is considering to be non-used if token balance, native balance, native and permit nonces are zero.
```typescript
async getNonusedEphemeralIndex(): Promise
```
### Returns
`Promise` returns index of the first non-used ephemeral address.
### Example
```typescript
const idx = await getNonusedEphemeralIndex();
console.log(`Found nonused ephemeral address at index ${idx}`);
// output: Found nonused ephemeral address at index 3
```
## Getting Ephemeral Address at Index
The library generates ephemeral addresses with [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki) (hierarchical deterministic wallets). So the every address has an index (the last HD path component).
```typescript
async getEphemeralAddress(index: number): Promise
```
### Parameters
`index` - an index of requested ephemeral address.
### Returns
`Promise` returns [EphemeralAddress](/implementation/client-library-sdk/common-types.md#ephemeral-address) object.
### Example
```typescript
const ephAddr = await getEphemeralAddress(0);
console.log(`First ephemeral address: ${ephAddr.address}`);
// output: First ephemeral address: 0x8ff66a5491a15ac67c596d1e9a6290e56dd4d156
```
## Getting All Used Ephemeral Addresses
Request details of all ephemeral addresses which were already used.
```typescript
async getUsedEphemeralAddresses(): Promise
```
### Returns
`Promise` returns array of [EphemeralAddress](/implementation/client-library-sdk/common-types.md#ephemeral-address) objects.
### Example
```typescript
const used = await getUsedEphemeralAddresses();
console.log(`$Used addresses: {used.map((a) => a.address).join(`,\n`)}`);
// output: Used addresses: 0x8ff66a5491a15ac67c596d1e9a6290e56dd4d156,
// 0x8434e839e0fa967fb7b9f624c381d533bcbce05d,
// 0xa78b9d09b307a972cae3be39f9182b7065fb15f4
```
## Retrieving Number of Token Transfers To the Address
```typescript
async getEphemeralAddressInTxCount(index: number): Promise
```
### Parameters
`index` - an index of the ephemeral address.
### Returns
`Promise` returns number of incoming token transfers to the ephemeral address with the requested index.
### Example
```typescript
const cnt = await getEphemeralAddressInTxCount(0);
console.log(`Incoming token transfers: ${cnt}`);
// output: Incoming token transfers: 1
```
## Retrieving Number of Token Transfers From the Address
```typescript
async getEphemeralAddressInTxCount(index: number): Promise
```
### Parameters
`index` - an index of the ephemeral address
### Returns
`Promise` returns number of outgoing token transfers to the ephemeral address with the requested index.
### Example
```typescript
const cnt = await getEphemeralAddressInTxCount(0);
console.log(`Outgoing token transfers: ${cnt}`);
// output: Outgoing token transfers: 1
```
## Getting the Ephemeral Address Private Key
{% hint style="danger" %}
Use this method only for emergency reasons. Everyone who has the private key has full control over the funds on that ephemeral address.
{% endhint %}
```typescript
getEphemeralAddressPrivateKey(index: number): string
```
### Parameters
`index` - an index of the ephemeral address
### Returns
A string with the private key in the hex representation
### Example
```typescript
const privKey = getEphemeralAddressPrivateKey(1);
console.log(`Private key: ${privKey}`);
// output: Private key: 2c7c5924e695bd0aad2145641f92fe3d95faf13d236dba7978c138fb6045ba3c
```
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.zkbob.com/implementation/client-library-sdk/full-mode-operations/ephemeral-deposits.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.