Hawkynt

TPypy (DarkCrypt)

Tweaked-IV-setup variant of Pypy by Biham and Seberry (2007), the strongest published member of the Py family: Pypy’s single-word-per-round output function combined with the fixed equivalent-IV setup. As implemented in the DarkCrypt Total Commander plugin, which hardcodes a 512-bit key and 512-bit IV.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Rolling-Array Stream Cipher
Security status	Not classified
Complexity	Advanced
Inventor	Eli Biham, Jennifer Seberry
Year	2007
Origin	🇮🇱 Israel
Source	algorithms/stream/darkcrypt-tpypy.js

Parameters

Parameter	Supported values
Key sizes	64 bytes (512 bits)
Nonce sizes	64 bytes (512 bits)

Security

Status: not classified — treat as unverified.

Known vulnerabilities

Issue	Description	Mitigation
Distinguishing attacks	Sekar, Paul and Preneel, and Rose/Crowley/Paul, published distinguishing attacks on TPypy’s pseudorandom bit generation.	Use a vetted modern cipher.

Documentation

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

References

• Biham, Seberry - “Tweaking the IV Setup of the Py Family of Stream Ciphers”
• DarkCrypt plugin (Total Commander PlugRing)

Test vectors

1 vector ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — DarkCrypt TPypy keystream

Field	Value
iv	00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
key	000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input	00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
expected	e1f7caf9269f05a530dd0cd86eea4ec2 5d10deb2e90b6aeb7273d965a72f08e7 15bccad5f79cfdec61dc21b02a6d09b6 2f942987ee09124fdce0d1669ac9c09c 0ad3dabdef6d7d7d3cf36d89b001d20b 1e263b4221934ed48776bf856a3f8440 47b78623e31c6c4c5812379f14307ea7 95d379a005c91c24ddb1eff4a3135bd1

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