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ISIN Validator Field Guide: When Three Layers Hide Behind One Luhn Check
Twelve Characters, Three Layers, One Luhn Check A single ISIN travels through three concentric validation…
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XML to JSON Converter Field Guide: Five Toggles, Eight Questions, Zero Silent Loss
Eight pre-flight questions catch silent loss before you commit. Five toggles decide whether your downstream code sees the document you have or a quietly wrong version of it.
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Text Hash Generator Field Guide: When MD5 Collides With Your Build, the SHA-256 Fingerprint Is the One That Saves You
MD5 still ships in production code, but the day it collides with your build, the…
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Mod-11 Checksum Calculator Field Guide: ISBN-10, fodselsnummer, and the X check digit
The Mod-11 check digit is the quiet workhorse behind ISBN-10, ISBT-128 blood bags, Norwegian fødselsnummer,…
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Stop Giving One Person the Recovery Key: A Practical 3-of-5 Shamir Design
A practical guide to splitting a recovery secret with Shamir Secret Sharing, choosing a 3-of-5 threshold, understanding the GF(256) implementation, and adding the integrity checks the scheme does not provide.
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The 32-bit Fingerprint Your Computer Uses a Billion Times a Day: A CRC32 Field Guide
CRC32 is not a hash. It is the cheapest integrity check in computing, and the reason ZIP, PNG, gzip, and Ethernet all know when something went wrong.
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IBAN Validator: The Three Decisions That Decide Whether a Bank Account Number Is Real
Country code, length, mod-97. Three decisions in a strict order — the only structure an IBAN validator needs to catch every typo without rejecting valid numbers.
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The orphaned records hiding in your database will cost you a migration
Your orders table says customer 47,847 placed 312 orders last year. Your customers table says…
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Data Interpolator: The Three Settings That Decide Whether an Interpolated Column Is Honest
You paste a CSV into a tool, leave one field on "auto," and get a…
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The Three Digits Most SSN Validators Get Wrong: Why 666-12-3456 and 900-Series Numbers Slip Through
The Three Digits Most SSN Validators Get Wrong You paste 123-45-6789 into a form, the…