Hawkynt

Py6 (DarkCrypt)

Reduced-state variant of Py by Biham and Seberry: a 64-entry (6-bit) rolling permutation P and a 68-entry rolling word array Y, same round structure and two-word output as Py but far cheaper key/IV setup. Ported from the DarkCrypt Total Commander plugin, which hardcodes a 256-bit key and 256-bit IV.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Rolling-Array Stream Cipher
Security status	❌ Broken
Complexity	Advanced
Inventor	Eli Biham, Jennifer Seberry
Year	2005
Origin	🇮🇱 Israel
Source	algorithms/stream/darkcrypt-py6.js

Parameters

Parameter	Supported values
Key sizes	32 bytes (256 bits)
Nonce sizes	32 bytes (256 bits)

Security

Status: ❌ Broken

Known vulnerabilities

Issue	Description	Mitigation
Distinguishing / key-recovery attacks	Py6 shares Py’s broken IV setup and was superseded by the tweaked TPy6.	Use TPy6 or a vetted modern cipher.

Documentation

• eSTREAM Py Phase 2 page
• Py (cipher) - Wikipedia
• DarkCrypt plugin (Total Commander PlugRing)

References

• Biham, Seberry - C Code of Py6, eSTREAM submission package
• DarkCrypt plugin (Total Commander PlugRing)

Test vectors

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

Vector 1 — DarkCrypt Py6 keystream

Field	Value
iv	0000000000000000000000000000000000000000000000000000000000000000
key	000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f
input	00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
expected	76f4f37ef99618f05f6e37915b5f155b 11baa364135804add08f5993c755c704 b7fdc77ef8f8c05f290c039847874a90 2e043e337ecad27bdee53ecb4a1d9906 f9953c55c6c5847b11e6e8d129d96086 eb78d2980ae6554e3dafff17422681a4 ca95ac40d0fbe93c2263887d87a80d6d 9ff19933f6ca642fa56cbcc42f58269b

Vector 2 — DarkCrypt Py6 — non-zero key and IV, 48-byte message (verified against the DarkCrypt implementation)

Field	Value
key	0b30557a9fc4e90e33587da2c7ec11365b80a5caef14395e83a8cdf2173c6186
iv	073c71a6db10457aafe4194e83b8ed22578cc1f62b6095caff34699ed3083d72
input	03203d5a7794b1ceeb0825425f7c99b6 d3f00d2a4764819ebbd8f5122f4c6986 a3c0ddfa1734516e8ba8c5e2ff1c3956
expected	6c3b779461499366b8845a1f6ddfe9f9 a349f9213ab91354b10c0bfa63330c42 edfcfdd300a47465bac2538464796484

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