CheckDigit
Ruby implementation of the Luhn, Damm and Verhoeff check digit algorithms
-
is the latest released version
- For the version under development (master), check version.rb
Installation
Add this line to your application's Gemfile:
gem 'check_digit'
And then execute:
$ bundle
Or install it yourself as:
$ gem install check_digit
Usage
Each implementation provides the same 2 class methods:
- checksum(num) - returns a new number with the checksum digit appended at the end
- valid?(num) - returns true if the number has a valid checksum digit, false if the number has an invalid checksum digit
Code sample:
require 'check_digit'
Damm.checksum(123) # returns 1234
Damm.valid?(1234) # returns true
Damm.valid?(1239) # returns false
Algorithm Comparison - Error Prevention
| Error Type | % of All Errors | Luhn | Damm | Verhoeff |
|---|---|---|---|---|
| single errors: a becomes b | 60% to 95% | 1 | 1 | 1 |
| omitting or adding a digit | 10% to 20% | 1 | 1 | 1 |
| adjacent transpositions: ab becomes ba | 10% to 20% | 2 | 1 | 1 |
| twin errors: aa becomes bb | 0.5% to 1.5% | 3 | 1 | 2 |
| jump transpositions: acb becomes bca | 0.5% to 1.5% | 2 | 1 | 2 |
| jump twin errors: aca becomes bcb | below 1% | 1 | 1 | 2 |
| phonetic errors: a0 becomes 0a | 0.5% to 1.5% | 1* | 1 | 2 |
Source: http://www.augustana.ab.ca/~mohrj/algorithms/checkdigit.html
* Not entirely sure if Luhn catches all phonetic errors, e.g. 13 instead of 30
Legend
- Prevents all errors
- Prevents most errors
- Prevents some errors
- Does not prevent any errors
Algorithm Comparison - Performance
50,000 iterations (time in seconds - lower is better)
| Algorithm | Generate | Validate |
|---|---|---|
| Luhn | 5.163268 | 5.085513 |
| Damm | 1.001179 | 0.996764 |
| Verhoeff | 2.496255 | 2.471240 |
* Test was on Linux 16.04 with 2.80GHz Intel Xeon E5-1603 using Ruby 2.4.1
Contributing
- Fork it ( https://github.com/elitwin/check_digit/fork )
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request
Attributions
The Verhoeff implementation was provided from this repo (https://github.com/bai/verhoeff) and was the inspiration for the interface (checksum, valid?) used by all the implementations