THE INRHYTHM OPPORTUNITY
This is one of the rarest assignments in mobile payments engineering. You will develop JavaCard applets deployed to secure element hardware for a leading global financial services company, with the applet accessed from an iOS host application. The software you write runs inside the chip and communicates with payment terminals at point of sale.
JavaCard applet development at this level requires deep command of GlobalPlatform card specifications, APDU protocols, and cryptographic operations on constrained hardware. You will work alongside an iOS engineering team that handles the host-side NFC communication via Core NFC. If you have shipped JavaCard applets to production secure elements, this engagement places your expertise at the core of payment infrastructure used by millions.
YOUR IMPACT
- The JavaCard applet you build is the software layer that communicates between a payment device and a point-of-sale terminal when a customer taps to pay.
- Your implementation directly determines the security posture and interoperability of payment credentials on secure element hardware at scale.
- The work supports an expanding multi-scheme payment capability that extends beyond the client's existing payment portfolio.
WHAT YOU WILL DO
- Design and develop JavaCard applets deployed to secure element hardware for contactless payment flows.
- Implement APDU command/response handling per ISO 7816 and GlobalPlatform Card Specification: SELECT, INITIALIZE UPDATE, EXTERNAL AUTHENTICATE, GET DATA, GENERATE AC.
- Manage secure element applet lifecycle: installation, personalization, key injection, and deletion per GlobalPlatform Card Specification.
- Write personalization scripts and key injection procedures for payment credential provisioning on target secure element hardware.
- Validate the terminal communication layer at the tap-to-pay interaction boundary, ensuring correct cryptogram exchange between the secure element and EMV-compliant terminals.
- Coordinate with the iOS engineering team to ensure consistent payment flow from the Core NFC host application through to terminal cryptogram verification at the SE boundary.
- Produce technical documentation covering applet architecture, key management procedures, APDU command set, and integration points.
- Participate in Agile sprint ceremonies and operate within the client's engineering standards; adapt quickly to client conventions and tooling preferences.
WHAT YOU WILL BRING
Must Have
- JavaCard applet development: 8+ years of total engineering experience with at least 3 years of dedicated JavaCard applet development shipped to production secure elements.
- GlobalPlatform Card Specification (GP 2.x or 2.3.x): hands-on experience with secure channel protocols, card content management, and applet lifecycle management.
- ISO 7816 APDU protocol: proficiency in command/response design and implementation, including status words and extended APDUs.
- JavaCard 3.0.x platform: practical command of JCRE runtime, package structure, persistent/transient object management, and cryptographic API (javacard.security, javacardx.crypto).
- Payment credential personalization: experience with key injection, key diversification algorithms, and personalization script generation for production SE deployments.
- EMV contactless payment flows: understanding of how secure element applets interact with terminal infrastructure at point of sale.
- Constrained hardware engineering: ability to work within JavaCard memory limits, transaction atomicity requirements, and applet sizing constraints.
Nice to Have
- iOS Core NFC (NFCTagReaderSession, NFCISO7816Tag): familiarity with how an iOS host application sends ISO 7816 APDU commands to SE-equipped hardware; understanding of the host-side of the tap-to-pay interaction.
- Swift or Objective-C: basic reading familiarity sufficient to collaborate with the iOS team on integration points and debug APDU exchange issues end-to-end.
- M/Chip, Visa payWave, or equivalent contactless payment network specifications.
- GlobalPlatform Trusted Execution Environment (TEE) experience in addition to SE.
- JavaCard test frameworks and applet simulation environments such as jCardSim.
- Payment network certification processes: EMVCo or equivalent scheme certification exposure.
- Location flexibility: willingness to work from or relocate to Pune or Bangalore, India.
THE INRHYTHM CONSULTANT
At InRhythm, consultants are more than technical executors. Every member of our team is expected to demonstrate:
- Strategic Thinking: Understand that your applet connects directly to the client's expansion of tap-to-pay capabilities across payment schemes. The work is not isolated R&D; it is production infrastructure.
- Clarity and Ownership: Applet quality, personalization script correctness, and terminal interoperability are your responsibility, not just the code you write but the outcomes it produces. When something is wrong at the terminal boundary, you own the diagnosis.
- Stakeholder Alignment: Work directly alongside the client engineering team and coordinate with the iOS engineers on the host-side NFC integration. Translate secure element architecture and APDU-level constraints into plain language for stakeholders who may not have deep JavaCard backgrounds.
- Bias to Measurable Outcomes: Orient your work toward results the client can see and measure: applet interoperability with EMV-compliant terminals, cryptogram correctness, personalization script reliability. Not activity for its own sake.
- Consultant Mindset: Bring structure to ambiguous technical requirements. This is a new program with evolving specifications. You work productively within those constraints and raise open questions constructively rather than waiting for direction.
