Hawkynt

ISIN

ISIN (International Securities Identification Number) check digit per ISO 6166. 12-character alphanumeric code (2 country + 9 identifier + 1 check) for global securities. Uses modified Luhn algorithm with letter-to-number conversion (A=10, B=11, …, Z=35).

Properties

Property	Value
Category	Checksums
Sub-category	Securities Identifier
Security status	🎓 Educational Only
Complexity	Intermediate
Inventor	International Organization for Standardization
Year	1989
Origin	Not specified
Source	`algorithms/checksum/isin-checksum.js`

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Notes

Format: CC123456789D (2 country + 9 ID + 1 check)
Country codes: ISO 3166-1 alpha-2 (e.g., US, GB, DE)
Letter conversion: A=10, B=11, …, Z=35
Algorithm: Modified Luhn on converted numeric string
Double every second digit from right to left
Sum individual digits if result > 9
Check digit: (10 - sum mod 10) mod 10
Example: US0378331005 (Apple Inc.)
Used in: Trading, clearing, settlement globally
Detects: All single-digit errors

Documentation

References

python-stdnum ISIN implementation

Test vectors

3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Apple Inc.

Field	Value
`input`	`5553303337383333313030`
`expected`	`05`

Vector 2 — British Airways GB0009753368

Field	Value
`input`	`4742303030393735333336`
`expected`	`08`

Vector 3 — German security

Source: ISIN check

Field	Value
`input`	`4445303030424159303031`
`expected`	`07`

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