Senior Security Engineer, Bitcoin Platform

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 50+ 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.
The Role
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.
You Will

• 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

• 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

We're working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We also consider qualified applicants with criminal histories for employment on our team, and always assess candidates on an individualized basis.
We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible. Want to learn more about what we're doing to build a workplace that is fair and square? Check out our I+D page .
Block will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and "fair chance" ordinances.
Block takes a market-based approach to pay, and pay may vary depending on your location. U.S locations are categorized into one of four zones based on a cost of labor index for that geographic area. The successful candidate's starting pay will be determined based on job-related skills, experience, qualifications, work location, and market conditions. These ranges may be modified in the future.
To find a location's zone designation, please refer to this resource . If a location of interest is not listed, please speak with a recruiter for additional information.
Zone A:
$198,000 - $297,000 USD
Zone B:
$188,100 - $282,100 USD
Zone C:
$178,200 - $267,400 USD
Zone D:
$168,300 - $252,500 USD
Block, Inc. (NYSE: SQ) is a global technology company with a focus on financial services. Made up of Square, Cash App, Spiral, TIDAL, and TBD, we build tools to help more people access the economy. Square helps sellers run and grow their businesses with its integrated ecosystem of commerce solutions, business software, and banking services. With Cash App, anyone can easily send, spend, or invest their money in stocks or Bitcoin. Spiral (formerly Square Crypto) builds and funds free, open-source Bitcoin projects. Artists use TIDAL to help them succeed as entrepreneurs and connect more deeply with fans. TBD is building an open developer platform to make it easier to access Bitcoin and other blockchain technologies without having to go through an institution.