Original title: FST Pay: Deterministic Safety-Gated Architecture for Youth Digital Payments
Shaikh Mohammed Burhan, Syed Farhaan Quadri, Tabassum Nahid Sultana · September 2026
Digital payments let teens manage money, but they also expose young people to impulsive spending, frauds, unauthorized charges, and merchant exploitation. Normal safety tools use either rigid limits or probabilistic machine learning. Letting unpredictable artificial intelligence systems decide on live payments causes critical audit flaws and erratic behavior in rare cases. To fix this, researchers designed FST Pay. The system uses a strict deterministic gate right on the payment path, while keeping artificial intelligence completely separate. Every transaction on networks like UPI must pass six fixed checks. These checks review spending caps, guardian co-sign rules, payment amounts, merchant categories, allowed times, and device hardware safety. The system sorts every purchase into ALLOW, REVIEW, or BLOCK. Risky payments require an asynchronous guardian co-sign, while generative artificial intelligence only creates post-settlement explanations.
A parent hands a teen a debit card but sets strict rules: no more than $20 per day, no video game stores, and no after 9 PM. The card checks each purchase against these rules instantly. If a purchase breaks a rule, the parent gets a text to approve or block it. Later, the card sends a summary of spending habits, but it never changes the transactions themselves. In this paper, the six invariant checks are like the parent's rules, and the generative AI is like the summary, powerless to alter any decisions.
Adolescents can safely learn financial responsibility with digital payments, protected by transparent, auditable rules. Parents set clear limits and approve risky transactions. Banks avoid unpredictable AI decisions that could lead to fraud or audit failures.
The abstract doesn't state explicit limitations of FST Pay. It describes the system as based on six invariant checks designed for UPI rails. It does not address what happens if a legitimate transaction is blocked or how to update rules without causing downtime. The effectiveness against sophisticated social engineering is not evaluated.
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FST Pay: Deterministic Safety-Gated Architecture for Youth Digital Payments — Shaikh Mohammed Burhan, Syed Farhaan Quadri, Tabassum Nahid Sultana
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.