1. Thunderrise
  2. Blog
  3. How to Build a P2P Payment App Like Square Cash
How to Build a P2P Payment App Like Square Cash

How to Build a P2P Payment App Like Square Cash


Mobile technologies are changing the way we look at money. Cash-free world is nearly within spitting distance. Now it’s shaped as a huge amount of mobile payment systems that provide users with real-time money exchange. Now there’s already no need in checkbooks and sooner, people won’t need even cash dispensers.

As we said above, there are a lot of payment apps around the world. Some of them are local and work for a particular region and some are world-recognised (PayPal, for example). Today, we are going to speak about payment applications and will take Square Cash as an example of successful representative.

What is Square Cash

Headquartered in San Francisco, CA, Square is a mobile payment company created in 2009 by Jack Dorsey and Jim McKelvey. Their dream was to make commerce easy. At the beginning, they were committed to the principle that every business should be able to make credit cards transactions. In 2015, Square has eventually reached the mark of $1 billion.

Square Cash allows users to exchange money with their friends in the most simple way. As a peer-to-peer application, it’s really convenient and easy to use. Sending money to a friend via Square Cash is often even faster than getting a wallet and counting out the needed sum of old faithful cash.

This app works in a really simple way. Imagine the situation when you pay for a dinner with your friend and, instead of counting down coins, you just send your part to your friends’ credit card from the phone. Here Square Cash as a P2P service plays the part of middleman.

How it technically works

From the technical view, Square Cash workflow can be divided on two sides: customer facing and backend. Let’s shortly talk them.

Square uses RFC 5321 SMTP server that transfers data between two parties: sender and receiver. The square currently achieves this via the Square Cash iOS or Android application and works together with a resident email application on the device to send a pre-delivered email message.

Sender fills the form to a receiver's email for an amount. The sender fills the form with the recipient of the e-mail address for the specified amount. Then Square generates an e-mail message that represents the amount that will be sent in the subject line of the letter with the recipient's address in the "To:" field and in the field cash@square.com in the "cc:" field. The sender can send a message in the body of the message.

Of course such operations require the presence of bank. Speaking about Square, their middleman bank is Chase Bank (Square Cash works only in US). There are some processes that are created on the top of SMTP server. It allows system to connect to Visa and MasterCard APIs used for transactions.


But there’s an obvious question: are P2P payments safe? As all the financial data is encrypted within the application that means that you can be assure of data safe. A lot of P2P services like Square Cash can boast their security and fraud monitoring. But no security system could warrant a 100% protection, so in case of theft you can turn to Square Cash support team that will help you resolve any problem. There are also some additional safety measures:

  • PCI DSS certificate that increase the whole credit card security industry
  • Push notifications about all your account activity. Found something suspicious? Turn to a support team
  • PIN codes, Touch ID and credit card CVV are used as a security lock feature

PCI DSS is a transaction security standard made by Visa, MasterCard, American Express and other major companies. Being certified by PCI DSS means that platform meets all necessary requirements for safe money transactions. Paying with Square Cash is as safe as common credit card or debit card transactions.

Features to implement

Let’s talk about some crucial aspects that every payment app like Square Cash should perform:

  • Users should have an ability to send money to their friends or third-parties not leaving the app
  • Application has to perform bank account synchronization
  • Protection measures like fingerprint scan or security code
  • Payment in online stores within the app

Creating a peer-to-peer payment application is a really hard task so you have to be ready for extra expenses. As always, the total cost of project development can vary. Factors include the team size, their expertise, hourly rate, their location and so on. For example, team from Silicon Valley charge $150 per hour of their work while Ukrainian developers work for $20/hour. So it’s really hard to predict the cost in dollars but the approximate time needed is 1000 hours. If you want to create a peer-to-peer payment platform like Square Cash, feel free to contact us and discuss the development.