Senior Security Engineer (Bitcoin Platform), Cash App

  • New York, NY, USA
  • Full-time
  • Alternate Location: San Francisco, United States
  • Current Square Employee?: Apply via go/jobs with your Square email.

Company Description

Cash App is the fastest growing financial brand in the world. Built to take the pain out of peer-to-peer payments, Cash App has gone from a simple product with a single purpose to a dynamic money app with over 30 million active monthly users. 

Loved by customers and by pop culture, we’ve held the #1 spot in finance on the App Store for almost two years, and our social media posts see more engagement in a day than most financial brands see in a year. 

With major offices in San Francisco, New York, St. Louis, Portland, Kitchener-Waterloo, and Melbourne, Cash App is bringing a better way to send, spend, and save to anyone who has ever sought an alternative to today’s banking system.

Job Description

Cash App is a mobile-first bank that ranks in the top 10 free apps in the app store with a rapidly growing user base and feature set. Our mission is to provide banking services to all, in particular those that are underserved.

The Cash Security team is a hands-on engineering-driven security team that embeds security engineers within key platform and product teams across Cash. As a security team, we collaborate on building and sharing security infrastructure, principles, and guidelines.

As a Security Engineer embedded in Bitcoin Platform, you’ll work within our Bitcoin Platform team to:

  • Co-design, co-build, and co-own the security mechanisms and features that we use to protect the entire lifecycle of our Bitcoin holdings in production and at scale
  • Co-design, co-build, and co-own security mechanisms and features in our bitcoin platform production services, written in Kotlin and running on AWS
  • Maintain and develop new capabilities for Subzero, our open-source cold storage system, including the embedded applications that execute on our HSMs


You have:

  • A strong motivation to contribute to a meaningful product that will fundamentally change the way people interact with financial institution
  • Strong desire to perform and grow as a security engineer, and mentor other engineers
  • Demonstrated technical initiative and leadership

Technologies we use and teach:

  • Bitcoin Core, Multi-signature, Bitcoin Script, PSBTs
  • AWS KMS and Google’s Tink Cryptographic API
  • Hardware Security Modules and nCipher CodeSafe application
  • Java 11 including JUnit, Hibernate, and Guice, Kotlin, C
  • AWS, Docker, Kubernetes, Terraform

Additional Information

Cash App treats all employees and job applicants equally. Every decision is based on merit, qualifications, and talent. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status. We will consider for employment qualified applicants with criminal histories in a manner consistent with each office’s corresponding state and city guidelines.