Card payment and 3-D Secure integration
Most of the work is making signatures deterministic across devices that were never consistent with each other, so what it takes depends on how many terminal types are in play. We look at the estate first, then quote it.
- Scope
- Gateway integration, POS estate, or reconciliation
- Typical
- Four to eight weeks for a single gateway
- Rollout
- Staged across terminals, with no downtime
- Start
- Free scope and a fixed price in three business days
FAST Terminal rollouts scripted, not scheduled branch by branch.
GOOD Signatures made deterministic before anything ships.
REACHABLE One integration, priced up front. No per-terminal licensing.
What we build
Signatures that cannot drift
Payment fields are canonicalized into one fixed order and normalized for case before signing. That sounds like a detail and it is the whole game: 3-D Secure requires an exact signature match, so two terminals serializing the same transaction differently will produce intermittent declines that look random and are not.
Operations that survive a retry
Every call that moves money carries an idempotency key, so a timeout followed by a retry settles once. Network failures during payment are normal rather than exceptional, and the difference between a system that expects them and one that does not is measured in double charges.
Reconciliation you find out about the same day
Settlement files are matched against expected transactions automatically, and exceptions raise an alert immediately. The expensive version of this problem is not the mismatch, it is discovering the mismatch six weeks later with no log detailed enough to explain it.
How we approach it
Payments work is unusual in that the failure mode is silence. A broken checkout is obvious within minutes, while a signing mismatch on one terminal type declines a small percentage of transactions indefinitely and shows up only as a slow drift in settlement.
So the work is built around making failure loud. Deterministic inputs, signed requests, idempotent operations, and alerting that fires on the exception rather than on the total. That ordering matters more than which gateway is involved.
Questions on this work
How much does a 3-D Secure payment integration cost?
It depends almost entirely on how many terminal types are involved and how consistent they are, which is why we read the estate before quoting rather than after. A single gateway with a standard checkout is a matter of weeks. A multi-branch estate where every device serializes its fields differently is the larger job, because the work is making the signatures deterministic across all of them. Reading your setup and putting a fixed price on it costs nothing.
Why do 3-D Secure payments fail with a hash mismatch?
Almost always because the two sides serialized the request differently before signing. 3-D Secure requires an exact signature match, so a difference in field order, in character case, or in how an empty value is encoded produces a mismatch even though the payment data is identical. The fix is to canonicalize every field into one fixed order and normalize it before signing, so no device can desynchronize from the gateway.
Can you work with our existing gateway and terminals?
Yes, and that is the usual shape of the work. Most engagements start with an estate that already takes payments and has a specific problem: declines nobody can reproduce, settlement that does not balance, or a new terminal type that will not certify. Most of the value is in fixing what already runs, so that is usually where we start.