hardguard25 1.3.1

HardGuard25: A human-friendly unique ID alphabet. 25 unambiguous characters.

hardguard25

Python reference implementation of HardGuard25 — an open standard for human-safe identifiers.

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HardGuard25 is a 25-character alphabet designed so every symbol is visually distinct in any typeface, at any size, for any reader — including those with dyslexia. It removes 11 letters that cause real-world errors (I L O B S Z E T V X Q) so IDs survive handwriting, phone calls, OCR, and support tickets without corrections. When a letter and a digit compete for the same visual slot, the digit always wins.

Install

pip install hardguard25

Requires Python 3.9+.

Quickstart

from hardguard25 import generate, validate, normalize, check_digit, verify_check_digit

generate(8)                       # e.g. "AC3H7PUW"
generate(8, check_digit=True)     # e.g. "AC3H7PUWR"  (length+1)

validate("ac3h-7puw")             # True  (case and separators tolerated)
normalize("ac3h-7puw")            # "AC3H7PUW"

check_digit("AC3H7PUW")           # "R"
verify_check_digit("AC3H7PUWR")   # True

API

Function	Purpose
generate(length, *, check_digit=False)	Cryptographically secure random ID using rejection sampling for uniform distribution
validate(s)	True if s normalizes to a valid HardGuard25 ID; never raises
normalize(s)	Trim, uppercase, strip - _ . and spaces; raises ValueError on invalid chars
check_digit(code)	Mod-25 weighted check digit (ISO 7064 style)
verify_check_digit(code)	Strip last char, recompute, compare
ALPHABET	"0123456789ACDFGHJKMNPRUWY"

Type hints and py.typed marker included.

Sizing

Each character carries log2(25) = 4.64 bits of entropy.

Length	Bits	Unique IDs	Typical Use
4	18.6	390,625	Small inventory, tickets
5	23.2	9,765,625	Small business
6	27.9	244,140,625	Medium businesses
7	32.5	6.1 billion	Large catalogs
8	37.2	152.6 billion	Large systems
12	55.7	5.96 × 10¹⁶	Internal tokens
16	74.2	3.55 × 10²²	Cross-system IDs
20	92.8	2.11 × 10²⁷	Public tokens
22	102.1	1.32 × 10³⁰	Internet-scale

Recommended defaults:

• 16 for internal systems up to millions of IDs
• 20 for public tokens or cross-org use
• 22 for long-lived, internet-scale identifiers

See the spec for collision-bound tables.

When NOT to Use HardGuard25

• Cryptographic keys (use proper key derivation)
• Blockchain consensus (use domain-specific formats)
• Systems requiring global UUID guarantees (use UUIDv7 or ULID)
• Machine-only contexts where no human ever sees the ID

Reference

• Spec: https://github.com/snapsynapse/hardguard25/blob/main/SPEC.md
• Homepage: https://hardguard25.com/
• Source: https://github.com/snapsynapse/hardguard25
• Other languages: JavaScript, Go (same repo)

License

MIT