Find different inputs sharing check values.
Initialising algorithm engine for Checksum Collision Explorer...
How Checksum Collision Explorer Works?
The Checksum Collision Explorer finds different payloads with the same check character. It uses the chosen algorithm for each payload. A collision shows a change that the algorithm cannot detect.
- 1Enter a payload and select the algorithm.
- 2Generate variants: substitutions, swaps, twin errors, or random changes.
- 3Compute the check character of each variant.
- 4Keep variants whose check character equals the original.
- 5Group collisions by error type.
Checksum Collision Explorer Formula
The collision rule is x ≠ y and f(x) = f(y).
Collision(x, y) ⇔ x ≠ y ∧ f(x) = f(y) For a 1-digit check: P(random collision) = 1/10
fis the check algorithm.
f(1090) = 0 f(1900) = 0 Different payloads, same check digit → collision
Checksum Collision Explorer Conversion Table
The Collision Explorer table lists payload pairs and whether each algorithm separates them.
| Algorithm | Payload A | Payload B | Error type | Check A | Check B | Collision |
|---|---|---|---|---|---|---|
| Luhn | 1090 | 1900 | 09 ↔ 90 swap | 0 | 0 | Yes |
| GS1 Mod 10 | 1160 | 1610 | Digits differ by 5 | 0 | 0 | Yes |
| Luhn | 123456 | 123465 | 56 ↔ 65 swap | 6 | 7 | No |
| Simple sum mod 10 | 1234 | 4321 | Any reordering | 0 | 0 | Yes |
| Damm | 1234 | 1243 | 34 ↔ 43 swap | 0 | 6 | No |
| Verhoeff | 1234 | 1243 | 34 ↔ 43 swap | 0 | 1 | No |
What is Checksum Collision Explorer?
A Checksum Collision Explorer is a tool that finds distinct inputs sharing the same check value. Collisions are unavoidable: a single decimal digit splits all payloads into only 10 groups.
The goal of a good algorithm is to keep the most common human errors out of the same group, not to remove collisions entirely.
What are the uses of Checksum Collision Explorer?
There are 3 main uses of the Checksum Collision Explorer, including weakness analysis, fraud review, and teaching.
- Weakness analysis: Engineers list error types a scheme misses.
- Fraud review: Investigators check whether an altered number still passes.
- Teaching: Instructors show the limits of 1-digit checks.