Cryptomeria/C2 cipher (4C Entity) as implemented in the DarkCrypt Total Commander plugin: 10-round Feistel network, 56-bit key (of a 64-bit key slot), 64-bit block. Round function combines an S-box lookup with 8-bit and 32-bit rotations. The structure matches the published C2 specification exactly (add-based Feistel, S-box driven key schedule with a 17-bit 56-bit register rotation).
| Property | Value |
|---|---|
| Category | Block Ciphers |
| Sub-category | Block Cipher |
| Security status | 🎓 Educational Only |
| Complexity | Intermediate |
| Inventor | 4C Entity, LLC (Cryptomeria/C2 specification); DarkCrypt port by Alexander Myasnikov |
| Year | 2003 |
| Origin | 🇷🇺 Russia |
| Source | algorithms/block/darkcrypt-c2.js |
| Parameter | Supported values |
|---|---|
| Key sizes | 8 bytes (64 bits) |
| Block sizes | 8 bytes (64 bits) |
Status: 🎓 Educational Only
| Issue | Description | Mitigation |
|---|---|---|
| Proprietary S-box substituted | DarkCrypt uses its own constant table instead of the 4C Entity’s licensed production S-box; the real C2 cipher’s security also depends on that secret S-box remaining unpublished. | Use AES or another vetted cipher. |
| Short effective key | Only 56 bits of the 64-bit key slot are used, making brute-force key search feasible. | Use a cipher with at least 128-bit keys. |
3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — DarkCrypt C2 — zero key/plaintext
| Field | Value |
|---|---|
key |
0000000000000000 |
input |
0000000000000000 |
expected |
afa7ed3f67eecbc0 |
Vector 2 — DarkCrypt C2 — incrementing key/plaintext
| Field | Value |
|---|---|
key |
0001020304050607 |
input |
0001020304050607 |
expected |
78b03362d08db481 |
Vector 3 — DarkCrypt C2 — shifted incrementing key/plaintext
| Field | Value |
|---|---|
key |
0102030405060708 |
input |
1011121314151617 |
expected |
7f6eefe40d2021c9 |