Hawkynt

CUSIP

CUSIP (Committee on Uniform Securities Identification Procedures) check digit calculation. 9-character alphanumeric identifier for North American securities. Uses modified Luhn algorithm with position-based doubling. Standard for stocks, bonds, mutual funds in US and Canada.

Properties

Property	Value
Category	Checksums
Sub-category	Financial Identifier
Security status	🎓 Educational Only
Complexity	Intermediate
Inventor	American Bankers Association
Year	1968
Origin	🇺🇸 United States
Source	`algorithms/checksum/cusip-checksum.js`

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Notes

Format: 6 issuer ID + 2 issue ID + 1 check digit
Character values: 0-9 = numeric, A-Z = 10-35, * = 36, @ = 37, # = 38
Algorithm: Similar to Luhn, but doubles even positions (2,4,6,8)
If doubled value > 9, sum its digits (e.g., 16 → 1+6 = 7)
Check digit: (10 - sum mod 10) mod 10
Used in: US and Canadian financial markets
Mandatory for: SEC filings, trade reporting
Example: 037833100 (Apple Inc.)
Detects: All single-digit errors

Documentation

References

python-stdnum CUSIP implementation

Test vectors

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

Vector 1 — Apple Inc. (037833100)

Field	Value
`input`	`3033373833333130`
`expected`	`00`

Vector 2 — Cisco Systems (17275R102)

Field	Value
`input`	`3137323735523130`
`expected`	`02`

Vector 3 — Google Inc. (38259P508)

Field	Value
`input`	`3338323539503530`
`expected`	`08`

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