# List XRP as an Exchange This document describes the steps that an exchange needs to take to list XRP. These steps are targeted at *custodial exchanges* that hold funds on behalf of users, and allows users to deposit, withdraw, and trade other digital assets, fiat currencies, or other types of asset. ## Alpha Exchange For illustrative purposes, this document uses a fictitious business called *Alpha Exchange* to explain the high-level steps required to list XRP. For the purposes of this document, Alpha Exchange: * Currently specializes in listing BTC/USD * Wants to add BTC/XRP and XRP/USD trading pairs * Maintains balances for all of its customers * Maintains balances for each of its supported currencies ### User Benefits Alpha Exchange wants to list BTC/XRP and XRP/USD trading pairs partially because listing these pairs benefits its users. Specifically, this support wants to enable its users to: * Deposit XRP *to* Alpha Exchange *from* the XRP Ledger * Withdraw XRP *from* Alpha Exchange *to* the XRP Ledger * Trade XRP with other currencies, such as BTC, USD, among others ## Prerequisites for Supporting XRP To support XRP, Alpha Exchange must: * Create and maintain new [accounts](#accounts) * Create and maintain [balance sheets](#balance-sheets) See also: * [Compliance Guidelines](/docs/concepts/tokens/fungible-tokens/stablecoins/compliance-guidelines) — Token issuers and exchanges are different, but exchanges should also ensure that they are complying with local regulations and reporting to the appropriate agencies. * [Precautions](/docs/concepts/tokens/fungible-tokens/stablecoins/precautions) ### Partial Payments Before integrating, exchanges should be aware of the [partial payments](/docs/concepts/payment-types/partial-payments) feature. This feature allows XRP Ledger users to send successful payments that reduce the amount received instead of increasing the `SendMax`. This feature can be useful for [returning payments](/docs/concepts/payment-types/bouncing-payments) without incurring additional cost as the sender. #### Partial Payments Warning When the [`tfPartialPayment` flag](/docs/references/protocol/transactions/types/payment#payment-flags) is enabled, the `Amount` field ***is not guaranteed to be the amount received***. The `delivered_amount` field of a payment's metadata indicates the amount of currency actually received by the destination account. When receiving a payment, use `delivered_amount` instead of the Amount field to determine how much your account received instead. Be aware that malicious actors could exploit this. For more information, see [Partial Payments](/docs/concepts/payment-types/partial-payments). ### Accounts XRP is held in *accounts* (also referred to as *wallets* or *addresses* ) on the XRP Ledger. Accounts on the XRP Ledger are different than accounts on other blockchain ledgers, such as Bitcoin, where accounts incur little to no overhead. In the XRP Ledger, account state is stored per ledger and accounts are [not easy to delete](/docs/concepts/accounts/deleting-accounts). To offset the costs associated with storing accounts, each account must hold a separate [reserve of XRP](/docs/concepts/accounts/reserves) that cannot be sent to others. For these reasons, Ripple recommends that institutions not create excessive or needless accounts. To follow Ripple's recommended best practices, Alpha Exchange should create at least two new accounts on the XRP Ledger. To minimize the risks associated with a compromised secret key, Ripple recommends creating [*cold*, *hot*, and *warm* accounts](/docs/concepts/accounts/account-types) (these are sometimes referred to, respectively, as cold, hot, and warm wallets). The hot/warm/cold model is intended to balance security and convenience. Exchanges listing XRP should create the following accounts: * A [*cold wallet*](/docs/concepts/accounts/account-types#issuing-address) to securely hold the majority of XRP and customers' funds. For exchanges, this is also the address to which its users send [deposits](#deposit-xrp-into-exchange). To provide optimal security, this account's secret key should be offline. If a malicious actor compromises an exchange's cold wallet, the possible consequences are: * The malicious actor gets full access to all XRP in the cold wallet. * If the master key is compromised, the malicious actor can irrevocably take control of the cold wallet forever (by disabling the master key and setting a new regular key or signer list). This would also give the malicious actor control over all future XRP received by the cold wallet. * If this happens, the exchange has to make a new cold wallet address and tell its customers the new address. * If the regular key or signer list are compromised, the exchange can regain control of the cold wallet. However, some of a malicious actor's actions cannot easily be undone: * The malicious actor could issue tokens in the XRP Ledger by using the cold wallet, but those tokens should not be valued by anyone (unless the exchange is also a token issuer). * If a malicious actor enables the [Authorized Trust Lines](/docs/concepts/tokens/fungible-tokens/authorized-trust-lines) setting for the account, that cannot be unset, although this only relates to issuing tokens and should not affect an exchange that is not also an issuer. Any other settings a malicious actor changes with a master key can be reverted. * One or more [*hot wallets*](/docs/concepts/accounts/account-types#operational-addresses) to conduct the day-to-day business of managing customers' XRP withdrawals and deposits. For example, with a hot wallet, exchanges can securely support these types of automated XRP transfers. Hot wallets need to be online to service instant withdrawal requests. For more information about the possible consequences of a compromised hot wallet, see [Operational Account Compromise](/docs/concepts/accounts/account-types#operational-address-compromise). * Optionally, one or more warm wallets to provide an additional layer of security between the cold and hot wallets. Unlike a hot wallet, the secret key of a warm wallet does not need to be online. Additionally, you can distribute the secret keys for the warm wallet to several different people and implement [multi-signing](/docs/concepts/accounts/multi-signing) to increase security. For more information about the possible consequences of a compromised warm wallet, see [Standby Account Compromise](/docs/concepts/accounts/account-types#standby-address-compromise). See also: * [Issuing and Operational Addresses](/docs/concepts/accounts/account-types) * [Creating Accounts](/docs/concepts/accounts#creating-accounts) * [Reserves](/docs/concepts/accounts/reserves) ### Balance Sheets To custody its customers' XRP, Alpha Exchange must track each customer's XRP balance and its own holdings. To do this, Alpha Exchange must create and maintain an additional balance sheet or accounting system. The following table illustrates what this balance sheet might look like. The new XRP Ledger accounts (*Alpha Hot*, *Alpha Warm*, *Alpha Cold*) are in the *User* column of the *XRP Balances on XRP Ledger* table. The *Alpha Exchange XRP Balances* table represents new, additional balance sheet. Alpha Exchange’s software manages their users’ balances of XRP on this accounting system. table tr td b i XRP Balances on XRP Ledger td td td b i Alpha Exchange XRP Balances td td tr td b User td b Balance td td b Account # td b User td b Balance tr td Dave td 25,000 td td 123 td Alice td 0 tr td Edward td 45,000 td td 456 td Bob td 0 tr td Charlie td 50,000 td td 789 td Charlie td 0 tr td i Alpha Hot td 0 td td ... td td tr td i Alpha Warm td 0 td td td td tr td i Alpha Cold td 0 td td td td tr td ... td td td td td #### XRP Amounts Amounts of XRP are represented on the XRP Ledger as an unsigned integer count of *drops*, where one XRP is 1,000,000 drops. Ripple recommends that software store XRP balances as integer amounts of drops, and perform integer arithmetic on these values. However, user interfaces should present balances in units of XRP. One drop (.000001 XRP) cannot be further subdivided. Keep this in mind when calculating and displaying FX rates between XRP and other assets. For more information, see [Specifying Currency Amounts](/docs/references/protocol/data-types/basic-data-types#specifying-currency-amounts). #### On-Ledger and Off-Ledger With exchanges like *Alpha Exchange*, XRP can be "on-ledger" or "off-ledger": * **On-Ledger XRP**: XRP that can be queried through the public XRP Ledger by specifying the public [address](/docs/concepts/accounts/addresses) of the XRP holder. The counterparty to these balances is the XRP Ledger. For more information, see [XRP](/docs/introduction/what-is-xrp). * **Off-Ledger XRP**: XRP that is held by the accounting system of an exchange and can be queried through the exchange interface. Off-ledger XRP balances are credit-based. The counterparty is the exchange holding the XRP. Off-ledger XRP balances are traded between the participants of an exchange. To support these trades, the exchange must hold a balance of *on-ledger XRP* equal to the aggregate amount of *off-ledger XRP* that it makes available for trade. ## Flow of Funds The remaining sections describe how funds flow through the accounts managed by Alpha Exchange as its users begin to deposit, trade, and redeem XRP balances. To illustrate the flow of funds, this document uses the tables introduced in the ["Balance Sheets" section](#balance-sheets). There are four main steps involved in an exchange's typical flow of funds: 1. [Deposit XRP into Exchange](#deposit-xrp-into-exchange) 2. [Rebalance XRP Holdings](#rebalance-xrp-holdings) 3. [Withdraw XRP from Exchange](#withdraw-xrp-from-exchange) 4. [Trade XRP on the Exchange](#trade-xrp-on-the-exchange) This list does not include the [prerequisites](#prerequisites-for-supporting-xrp) required of an exchange. At this point, *Alpha Exchange* has created [hot, warm, and cold wallets](#accounts) on the XRP Ledger and added them to its balance sheet, but has not accepted any deposits from its users. table tr td b i XRP Balances on XRP Ledger td td td b i Alpha Exchange XRP Balances td td tr td b User td b Balance td td b Account # td b User td b Balance tr td Dave td 25,000 td td 123 td Alice td 0 tr td Edward td 45,000 td td 456 td Bob td 0 tr td Charlie td 50,000 td td 789 td Charlie td 0 tr td i Alpha Hot td 0 td td ... td td tr td i Alpha Warm td 0 td td td td tr td i Alpha Cold td 0 td td td td tr td ... td td td td td ### Deposit XRP into Exchange To track [off-ledger XRP balances](#on-ledger-and-off-ledger), exchanges need to create new [balance sheets](#balance-sheets) (or similar accounting systems). The following table illustrates the balance changes that take place on Alpha Exchange's new balance sheet as users begin to deposit XRP. A user named Charlie wants to deposit 50,000 XRP to Alpha Exchange. Doing this involves the following steps: 1. Charlie submits a payment of 50,000 XRP to Alpha Exchange's [cold wallet](#accounts). a. Charlie adds an identifier (in this case, `789`) to the payment to associate it with his account at Alpha Exchange. This is called a [*destination tag*](/docs/concepts/transactions/source-and-destination-tags). (To use this, Alpha Exchange should have set the `asfRequireDest` flag on all of its accounts to require all incoming payments to have a destination tag like Charlie's. For more information, see [AccountSet Flags](/docs/references/protocol/transactions/types/accountset#accountset-flags)). 2. The software at Alpha Exchange detects the incoming payment, and recognizes `789` as the destination tag for Charlie’s account. 3. When it detects the incoming payment, Alpha Exchange's software updates its balance sheet to indicate that the 50,000 XRP it received is controlled by Charlie. Charlie can now use up to 50,000 XRP on the exchange. For example, he can create offers to trade XRP with BTC or any of the other currencies Alpha Exchange supports. table tr td b i XRP Balances on XRP Ledger td td td b i Alpha Exchange XRP Balances td td tr td b User td b Balance td td b Account # td b User td b Balance tr td Dave td 25,000 td td 123 td Alice td 0 tr td Edward td 45,000 td td 456 td Bob td 0 tr td Charlie td s 100,000 br 50,000 td td 789 td Charlie td s 0 br 50,000 tr td td td td td td tr td Alpha Hot td 0 td td ... td td tr td Alpha Warm td 0 td td td td tr td Alpha Cold td s 0 br 50,000 td td td td tr td ... td td td td td ### Trade XRP on the Exchange Alpha Exchange users (like Charlie) can trade credit-based balances on Alpha Exchange. Alpha Exchange should keep track of user balances on its new balance sheet as these trades are made. These trades are *off-ledger* and independent from the XRP Ledger, so the balance changes are not recorded on the XRP Ledger. Customers who hold XRP in their own XRP Ledger accounts can also use the distributed exchange built into the XRP Ledger to trade currencies issued by gateways. For more information about trading *on* the XRP Ledger, see [Lifecycle of an Offer](/docs/concepts/tokens/decentralized-exchange/offers#lifecycle-of-an-offer). ### Rebalance XRP Holdings Exchanges can adjust the balances between their hot and cold wallets at any time. Each balance adjustment consumes a [transaction cost](/docs/concepts/transactions/transaction-cost), but does not otherwise affect the aggregate balance of all the accounts. The aggregate, on-ledger balance should always exceed the total balance available for trade on the exchange. (The excess should be enough to cover the XRP Ledger's transaction costs.) The following table demonstrates a balance adjustment of 80,000 XRP (via a [Payment transaction](/docs/references/protocol/transactions/types/payment) on the XRP Ledger) between Alpha Exchange's cold wallet and its hot wallet, where the cold wallet was debited and the hot wallet was credited. If the payment were reversed (debiting the hot wallet and crediting the cold wallet), the hot wallet balance would decrease. Balance adjustments like these allow an exchange to limit the risks associated with holding XRP in online hot wallets. table tr td b i Alpha Exchange XRP Off-Ledger Balances td td td td b i Alpha Exchange XRP On-Ledger Balances td tr td b Account # td b User td b Balance td td b XRP Ledger Account td b Balance tr td 123 td Alice td 80,000 td td Hot td s 0 br 80,000 tr td 456 td Bob td 50,000 td td Warm td 0 tr td …. td td td td …. td tr td 789 td Charlie td 50,000 td td Cold td s 180,000 br 100,000 tr td td td td td td tr td ... td td td td ... td ### Withdraw XRP from Exchange Withdrawals allow an exchange's users to move XRP from the exchange's off-ledger balance sheet to an account on the XRP Ledger. In this example, Charlie withdraws 25,000 XRP from Alpha Exchange. This involves the following steps: 1. Charlie initiates the process on Alpha Exchange’s website. He provides instructions to transfer 25,000 XRP to a specific account on the XRP Ledger (named "Charlie XRP Ledger" in the following table). 2. In response to Charlie’s instructions, Alpha Exchange does the following: a. Debits the amount (25,000 XRP) from Charlie’s account on its off-ledger balance sheet b. Submits a payment on the XRP Ledger for the same amount (25,000 XRP), from Alpha Exchange's hot wallet to Charlie’s XRP Ledger account table tr td b i XRP Ledger On-Ledger XRP Balances td td td b i Alpha Exchange XRP Off-Ledger Balances td td td td b i Alpha Exchange XRP On-Ledger Balances td tr td b User td b Balance td td b Account # td b User td b Balance td td b XRP Ledger Account td b Balance tr td Dave td 25,000 td td 123 td Alice td 80,000 td td Hot td s 80,000 br 55,000 tr td Edward td 45,000 td td 456 td Bob td 50,000 td td Warm td 0 tr td …. td td td …. td td td td …. td tr td Charlie XRP Ledger td s 50,000 br 75,000 td td 789 td Charlie td s 50,000 br 25,000 td td Cold td 100,000 tr td td td td td td td td td tr td ... td td td ... td td td td ... td ## See Also - **Concepts:** - [Accounts](/docs/concepts/accounts) - [Direct XRP Payments](/docs/concepts/payment-types/direct-xrp-payments) - [Partial Payments](/docs/concepts/payment-types/partial-payments) - [Source and Destination Tags](/docs/concepts/transactions/source-and-destination-tags) - **Tutorials:** - [Install `rippled`](/docs/infrastructure/installation) - [Send XRP](/docs/tutorials/how-tos/send-xrp) - [Set Up Secure Signing](/docs/concepts/transactions/secure-signing) - [Monitor Incoming Payments with WebSocket](/docs/tutorials/http-websocket-apis/build-apps/monitor-incoming-payments-with-websocket) - **References:** - [Payment transaction](/docs/references/protocol/transactions/types/payment) - [account_info method](/docs/references/http-websocket-apis/public-api-methods/account-methods/account_info) - [AccountRoot object](/docs/references/protocol/ledger-data/ledger-entry-types/accountroot)