Hawkynt

Tyche

Fast cryptographic PRNG based on 20-round ChaCha cipher designed by Samuel Neves and Filipe Araujo (2011). Tyche passes PractRand and TestU01 BigCrush statistical test suites. Uses ChaCha quarter-round function with different initialization than standard ChaCha20.

Properties

Property	Value
Category	Random Number Generators
Sub-category	Pseudorandom Number Generator
Variant	Tyche
Security status	🧪 Experimental
Complexity	Advanced
Inventor	Samuel Neves, Filipe Araujo
Year	2011
Origin	Not specified
Source	algorithms/random/chacha.js

Parameters

Parameter	Supported values
Seed sizes	32 bytes (256 bits)

Capabilities

Flag	Value
IsDeterministic	Yes
IsCryptographicallySecure	Yes

Security

Status: 🧪 Experimental

No vulnerabilities are recorded for this implementation.

Documentation

• Tyche: Fast and Small Nonlinear Pseudorandom Number Generators (PPAM 2011)
• ChaCha: A variant of Salsa20
• Cryptography StackExchange: Tyche vs ChaCha

References

• Go runtime PRNG source code (ChaCha8)
• Rust rand_chacha crate

Test vectors

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

Vector 1 — Tyche with seed 0, stream 0: First 16 bytes

Field	Value
seed	0000000000000000
streamIndex	00000000
outputSize	16
input	null
expected	dbdcae836fde31bf714be8aba4b974ff

Vector 2 — Tyche with seed 1, stream 0: First 16 bytes

Field	Value
seed	0100000000000000
streamIndex	00000000
outputSize	16
input	null
expected	abbf5598b056862844653ebd5aa86b9c

Vector 3 — Tyche with seed 12345, stream 0: First 16 bytes

Field	Value
seed	3930000000000000
streamIndex	00000000
outputSize	16
input	null
expected	d7d0722e34863050d14334a5877d014c

Vector 4 — Tyche with seed 0xDEADBEEF, stream 1: First 16 bytes

Field	Value
seed	efbeadde00000000
streamIndex	01000000
outputSize	16
input	null
expected	8e24dfdb18a1d74d5bdf1e9d5b5585fc

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