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SFC32

Small Fast Counting (SFC32) is a high-quality PRNG by Chris Doty-Humphrey designed for the PractRand test suite. It combines a chaotic invertible mapping with a counter to guarantee no small cycles and passes rigorous statistical tests.

Properties

Property	Value
Category	Random Number Generators
Sub-category	Pseudo-Random Number Generator
Security status	🎓 Educational Only
Complexity	Intermediate
Inventor	Chris Doty-Humphrey
Year	2010
Origin	🇺🇸 United States
Source	algorithms/random/sfc.js

Parameters

Parameter	Supported values
Seed sizes	1 byte (8 bits) to 16 bytes (128 bits)

Capabilities

Flag	Value
IsDeterministic	Yes
IsCryptographicallySecure	No

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Documentation

• PractRand: Chris Doty-Humphrey’s PRNG Test Suite
• PractRand RNG Engines Documentation
• Apache Commons RNG Implementation
• JavaScript PRNG Implementations (bryc/code)

References

• NumPy SFC64 Implementation
• PractRand Statistical Test Suite
• TestU01 Statistical Testing

Test vectors

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

Vector 1 — Seed (1,2,3,4): First 5 outputs (20 bytes) - verified against SFC32 reference implementation

Field	Value
seed	00000001000000020000000300000004
outputSize	20
input	null
expected	0000000700000022036000600b421d78cc849c75

Vector 2 — Seed (0,0,0,1): First 10 outputs - minimal seed with counter=1

Field	Value
seed	00000000000000000000000000000001
outputSize	40
input	null
expected	00000001000000020000000c0120001f 0360b48399e14d9bd9c4e5de3f6d95a6 59390fb3004b9efb

Vector 3 — Seed (0x9E3779B9, 0x243F6A88, 0xB7E15162, 12): Standard test seed - first 8 outputs

Field	Value
seed	9e3779b9243f6a88b7e151620000000c
outputSize	32
input	null
expected	c276e44d9b1951bcdc0d8dd95fdf01a49ee74639d956e0048959f5a3a65a8e9d

Vector 4 — Seed (12345, 67890, 11111, 1): Common test values - first 12 outputs (discard first 12 per PractRand)

Field	Value
seed	000030390001093200002b670000000001
outputSize	48
input	null
expected	0001396c00029057d3ec8b58733481ed 214324f016ed3820ff9157416940350b db7782ec49733921410d3859a992c3af

Vector 5 — Seed (1,1,1,1): Identical seed values - first 6 outputs

Field	Value
seed	00000001000000010000000100000001
outputSize	24
input	null
expected	000000030000000c012000270480b48b9b0201e26ce50a5b

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