Senior Mobile Engineer, EsSolo Holdings

Banking POS

Banking point-of-sale software for Android terminals: EMV chip and NFC contactless card reading, PIN entry and ISO 8583 messaging, with sensitive card data encrypted on the device.

essolo-pos.yamlpayments

# essolo-pos.yaml
project: Banking POS
org: EsSolo Holdings
role: Senior Mobile Engineer
domain: [payments]
ships_to: [Android POS terminals]
stack:
  - Kotlin
  - Java
  - EMV
  - NFC
  - ISO 8583
  - Terminal vendor SDKs

Context

Alongside its white-label wallet and card apps, EsSolo ran banking POS software on Android terminals. This is the card-present side of the platform: the card is read by chip or tap, and the cardholder enters a PIN on the device.

What I owned

Built the banking POS app for Android terminals, natively in Kotlin and Java.
EMV chip and NFC contactless card reading.
Online PIN entry with PIN-block encryption, and the terminal key management behind it.
ISO 8583 messaging to the payment processor for authorisations and reversals.
Encrypted the sensitive card and financial data the terminal handled.
Integrated the terminal vendors' hardware SDKs for the card reader, PIN pad and receipt printer.