IBAN ↔ KNR / BLZ Calculator

Choose between Validator or Generator mode!

Convert between a valid german IBAN and its underlying German banking identifiers BLZ and KNR.

You may use your german debit card to validate it via IBAN → KNR + BLZ.
To generate a valid IBAN, please use the KNR + BLZ → IBAN.

Sensitive identifiers are masked before persistence for the conversion history database.

IBAN (22 digits) BLZ (8 digits)

Continuous Integration

        test_iban_to_knr_blz ... PASSED
        test_knr_blz_to_iban ... PASSED
        test_invalid_iban ... PASSED
        test_invalid_knr_blz ... PASSED
        test_validateChecksum ... PASSED

        ✔ All MIPS tests passed via GitHub CI.
        ✔ All Python frontend tests passed via GitHub CI.
        ✔ All Python backend tests passed via GitHub CI.

About This Tool

A verified implementation of a German IBAN validator and generator, built on deterministic MIPS execution. Now extended and exposed via a modern web API.

Implementation

Initial MIPS assembly implementation 2023

Written in MIPS assembly language
Executed via MARS simulator
Verified via local test suite

Extension Phase 1 2025

FastAPI backend as a thin execution and validation layer
Dockerized MIPS environment for reproducible execution
Automated test suite executed in GitHub CI

Extension Phase 2 2025

MIPS core IBAN extended, validation in IBAN to KNRBLZ mode
Implemented persistent conversion history backed by SQLite
Added structured logging alongside backend input validation
Deployed to AWS

German IBAN format

An IBAN (International Bank Account Number) uniquely identifies a bank account and embeds a checksum to detect input errors.

DE AA BBBBBBBB CCCCCCCCCC

DE — country code
AA — checksum digits
BBBBBBBB — BLZ (bank code)
CCCCCCCCCC — KNR (account number)

Conversion modes

Validator Mode: IBAN → KNR + BLZ

Parses a German IBAN, validates it via verify_iban and then extracts the embedded BLZ and KNR. It uses validate_checksum.

verify_iban, validate_checksum, iban2knr.asm

Generator Mode: KNR + BLZ → IBAN

Validates the inputs, computes the checksum using string-based modulo arithmetic, and outputs a fully valid German IBAN.

knr2iban.asm, moduloStr.asm, validateChecksum.asm