Utility Tools

A grab-bag of payment helpers — the ISO 8583 bitmap calculator, MDC hash, ZKA encryption, and the AS 2805 multi-tab calculator. Small, focused tools that close gaps left by the larger calculators.

Introduction

These utilities are organised under Tools → Payments. Most are single-purpose and self-explanatory, but the AS 2805 Calculator bundles several Australian payment-system primitives into a single tabbed interface.

ISO 8583 Bitmap Calculator

Visual editor for ISO 8583 primary and secondary bitmaps. Toggle each bit to mark which fields are present in a message; the tool produces the corresponding 8-byte (primary) or 16-byte (primary + secondary) hex bitmap.

Two-way operation

Bits → Hex — Click bits 1–128 in a 16×8 grid; the hex bitmap updates live.
Hex → Bits — Paste a hex bitmap and the tool highlights each set bit.

Indicators

Bit 1 indicates the secondary bitmap (bits 65–128). The tool turns it on automatically when a high bit is selected.
Each bit shows its number on hover, plus the standard ISO 8583-1987 / -1993 / -2003 field name when available.

Example

Selected bits: 2, 3, 4, 7, 11, 12, 13, 41, 42, 49, 64

Primary Bitmap (hex): 7220000003800001

MDC Hash Calculator

Computes Modification Detection Code hashes (MDC-2, MDC-4) over hex data. Used in some legacy authentication and integrity protocols.

Inputs

Variant — MDC-2 (one DES pass) or MDC-4 (two DES passes for stronger collision resistance).
Data — Hex input.

Output

16-byte hash for both MDC-2 and MDC-4 (the difference is internal rounds).
Intermediate digests shown for educational use.

Heads-up

MDC-2 / MDC-4 are largely obsolete. Use SHA-2 or SHA-3 for new designs (in the HMAC tool).

ZKA Encryption Tool

Implements the Zentraler Kreditausschuss (ZKA) crypto profile used by the German banking ecosystem.

Operations

ZKA Encrypt — Encrypt data under a ZKA-derived working key.
ZKA Decrypt — Reverse the operation.
Key Derivation — Derive ZKA session keys from master material.

AS2805 Calculator

A multi-tab tool covering the most commonly needed primitives from the Australian Standard AS 2805 payment-systems suite.

Tabs

Tab	Purpose
Generate Terminal Key Set	Build a full terminal key set (KEKs, PEK, MAK, DEK) from master inputs.
Translate PIN Block	Translate a PIN block from a source key (often DUKPT-derived) to a destination ZPK.
MAC	Compute an AS 2805.4 MAC over arbitrary message data.
OWF	One-Way Function transforms used in AS 2805 key handling.

Generate Terminal Key Set Walk-through

Open the AS2805 Calculator.
Switch to the Generate Terminal Key Set tab.
Enter the master keys provided by the acquirer (typically a TMK-equivalent and randomness sources).
Click Generate. The tool returns each working key and its KCV.
Use the resulting MAK in the MAC tab to test message integrity, or use the PEK in the Translate PIN Block tab.

Tip

AS 2805 PIN translation pairs naturally with the DUKPT ISO 9797 tool: derive the source DUKPT PEK there, then plug the result into the AS 2805 PIN translation tab.

Tips

The Bitmap Calculator is the fastest sanity check when an ISO 8583 host complains "field not present" — toggle the bit you expect and confirm the hex matches what you sent on the wire.
Combine the Bitmap Calculator with the Host Simulator: copy the hex bitmap into the simulator’s message inspector to isolate parsing issues.
The activity logs in each tool persist until you clear them — useful for capturing a sequence of intermediate values to share with a vendor support ticket.