Senior Security Engineer - Bitcoin Platform

Company Description
It all started with an idea at Block in 2013. Initially 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 ecosystem, developing unique financial products, including Afterpay/Clearpay, to provide a better way to send, spend, invest, borrow and save to our 47 million monthly active customers. We want to redefine the world's relationship with money to make it more relatable, instantly available, and universally accessible.
Today, Cash App has thousands of employees working globally across office and remote locations, with a culture geared toward innovation, collaboration and impact. We've been a distributed team since day one, and many of our roles can be done remotely from the countries where Cash App operates. No matter the location, we tailor our experience to ensure our employees are creative, productive, and happy.
Check out our locations, benefits, and more at cash.app/careers.
Job Description
Cash App has grown rapidly to tens of million of users moving billions of dollars daily. To support this incredible growth, we are growing the Security organization.
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 Engineering, you'll work within our Bitcoin Platform Engineering 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

Qualifications
You have (not all required):

• 8+ years of experience delivering quality software
• Experience writing security sensitive code or using cryptographic libraries
• Familiarity with security protocols or protocol implementation
• Experience with embedded systems, embedded C, firmware development or embedded security
• Experience with Secure Enclaves, TrustZone, SGX, AWS Nitro enclaves, HSMs, nCipher HSMs or Codesafe
• Experience building security-sensitive applications in AWS
• 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:

• Hardware Security Modules and nCipher CodeSafe application
• AWS KMS
• Google's Tink Cryptographic API
• C programming

Qualifications
You have (not all required):

• 8+ years of experience delivering quality software
• Experience writing security sensitive code or using cryptographic libraries
• Familiarity with security protocols or protocol implementation
• Experience with embedded systems, embedded C, firmware development or embedded security
• Experience with Secure Enclaves, TrustZone, SGX, AWS Nitro enclaves, HSMs, nCipher HSMs or Codesafe
• Experience building security-sensitive applications in AWS
• 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:

• Hardware Security Modules and nCipher CodeSafe application
• AWS KMS
• Google's Tink Cryptographic API
• C programming