Hawkynt

Letsief3 (DarkCrypt)

Letsief3 block cipher from the DarkCrypt Total Commander plugin. 6-round Feistel-like network over two 32-bit big-endian halves; the round function multiplies each half (modular multiply over 16-bit limbs) by two key-dependent 256-entry S-boxes and XORs a round subkey. 64-bit block, 512-bit key.

Properties

Property Value
Category Block Ciphers
Sub-category Block Cipher
Security status 🎓 Educational Only
Complexity Intermediate
Inventor Alexander Myasnikov (DarkCrypt / Zarya project)
Year 2013
Origin 🇷🇺 Russia
Source algorithms/block/darkcrypt-letsief3.js

Parameters

Parameter Supported values
Key sizes 64 bytes (512 bits)
Block sizes 8 bytes (64 bits)

Security

Status: 🎓 Educational Only

Known vulnerabilities

Issue Description Mitigation
Uniform keys are fixed points of the key schedule A key of 64 equal bytes 0x00, 0x33, 0x66, 0x99, 0xCC or 0xFF produces sixteen identical subkeys and two-valued S-boxes, leaving the all-zero block unencrypted. The all-zero key is worse still: roughly one block in seven is returned unchanged. Never use a key of repeated bytes; prefer a vetted cipher such as AES.
Non-standard / unanalyzed variant Proprietary DarkCrypt cipher with no public cryptanalysis; the small round count and reliance on key-dependent multiplicative S-boxes are unvetted. Not recommended for 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 Letsief — incrementing key/plaintext

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input 0001020304050607
expected 985e38bc074b9e16

Vector 2 — DarkCrypt Letsief — shifted incrementing key/plaintext

Field Value
key 0102030405060708090a0b0c0d0e0f10 1112131415161718191a1b1c1d1e1f20 2122232425262728292a2b2c2d2e2f30 3132333435363738393a3b3c3d3e3f40
input 1011121314151617
expected 2140ee72033560a9

Vector 3 — DarkCrypt Letsief — incrementing key, zero plaintext

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input 0000000000000000
expected f08a59fb6cac4051

Vector 4 — DarkCrypt Letsief — incrementing key, all-ones plaintext

Field Value
key 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
input ffffffffffffffff
expected de08d6dacc84f8df

Vector 5 — DarkCrypt Letsief — all-zero key leaves a repeated-nibble block unencrypted

Field Value
key 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
input aaaaaaaaaaaaaaaa
expected aaaaaaaaaaaaaaaa

Vector 6 — DarkCrypt Letsief — all-zero key, incrementing plaintext

Field Value
key 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
input 0001020304050607
expected 8e5a7ff704050607

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