Hawkynt

BJ-256 (DarkCrypt)

Homegrown ARX block cipher from the DarkCrypt Total Commander plugin with no public specification: an 8x32-bit-word (256-bit) block cipher whose key schedule is a raw identity copy of the 512-bit key into 16 round-key words, sandwiching a fully-unrolled keyless ARX mixing network between leading/trailing key whitening.

Properties

Property Value
Category Block Ciphers
Sub-category Block Cipher
Security status 🎓 Educational Only
Complexity Advanced
Inventor Alexander Myasnikov (“Zarya” project) — DarkCrypt original design, no public specification
Year 2009
Origin 🇷🇺 Russia
Source algorithms/block/darkcrypt-bj256.js

Parameters

Parameter Supported values
Key sizes 64 bytes (512 bits)
Block sizes 32 bytes (256 bits)

Security

Status: 🎓 Educational Only

Known vulnerabilities

Issue Description Mitigation
Encrypting half the key reveals the other half The key schedule is an identity copy and the mixing network is keyless, so the cipher is Even-Mansour over a public permutation and E_K(K[0..31]) = K[32..63] for every key. Anyone who can get that one block encrypted learns half the key outright, and knowing the permutation reduces the rest to a generic Even-Mansour attack. Use AES or another vetted cipher.
All-zero weak key The mixing network carries no round constants, so it fixes the all-zero state, and with an all-zero key the whitening XORs do nothing either. The all-zero block is returned unencrypted. Never use an all-zero key.
Unanalyzed proprietary design No public specification, cryptanalysis or design rationale exists for BJ-256; the key schedule performs no mixing at all (round keys are the raw key words). Not recommended for any real use. Use AES or another vetted cipher.

Documentation

Test vectors

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

Vector 1 — DarkCrypt Bj256 — shifted incrementing key/plaintext

Field Value
key 0102030405060708090a0b0c0d0e0f10 1112131415161718191a1b1c1d1e1f20 2122232425262728292a2b2c2d2e2f30 3132333435363738393a3b3c3d3e3f40
input 101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f
expected 4647490ce33a0ebb7707574d415cc6e9929ce981a37728826b815378b6ae7606

Vector 2 — DarkCrypt Bj256 — incrementing key, zero plaintext

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input 0000000000000000000000000000000000000000000000000000000000000000
expected 3b18c79b66ca26134f0e9c1d2fa880dfde6b57ae7a9247fd36de33e9ee684f5e

Vector 3 — DarkCrypt Bj256 — incrementing key, all-ones plaintext

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
expected fd4831071386b5408c17fd132c040cd43b7e94443ca66f871a2ff446795ae46c

Vector 4 — DarkCrypt Bj256 — all-zero key, repeated-nibble plaintext

Field Value
key 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
input aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
expected b8b262199b4bea042ab05a5b21f19042d67554de0cddbcf49405211c8f2ec810

Vector 5 — DarkCrypt Bj256 — all-ones key, zero plaintext

Field Value
key ffffffffffffffffffffffffffffffff ffffffffffffffffffffffffffffffff ffffffffffffffffffffffffffffffff ffffffffffffffffffffffffffffffff
input 0000000000000000000000000000000000000000000000000000000000000000
expected f1eb30d7e16b4331953e62a13244b0f10bf39499fb759de1aef5c6751c68fc16

Vector 6 — DarkCrypt Bj256 — encrypting the key’s first half returns its second half

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input 000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f
expected 202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f

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