Declassified NSA block cipher from 1998, originally designed for the Clipper chip. Uses unbalanced Feistel network with 32 rounds, 64-bit blocks, and 80-bit keys. Historical significance only.
| Property | Value |
|---|---|
| Category | Block Ciphers |
| Sub-category | Block Cipher |
| Security status | ❌ Broken |
| Complexity | Intermediate |
| Inventor | NSA (National Security Agency) |
| Year | 1987 |
| Origin | 🇺🇸 United States |
| Source | algorithms/block/skipjack.js |
| Parameter | Supported values |
|---|---|
| Key sizes | 10 bytes (80 bits) |
| Block sizes | 8 bytes (64 bits) |
Status: ❌ Broken
| Issue | Description | Mitigation |
|---|---|---|
| NIST Withdrawal | NIST approval withdrawn in 2015. Not approved for new cryptographic protection | Use modern standardized ciphers like AES |
| Differential Cryptanalysis | Vulnerable to differential attacks with reduced complexity | Algorithm is deprecated - do not use for any security applications |
| Related-key attacks | Weak key schedule allows related-key attacks | Historical and educational interest only |
5 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — DarkCrypt Skipjack vector 1/zero
| Field | Value |
|---|---|
key |
00000000000000000000 |
input |
0000000000000000 |
expected |
aaae8ede6764143d |
Vector 2 — DarkCrypt Skipjack vector 2/incr
| Field | Value |
|---|---|
key |
00010203040506070809 |
input |
0001020304050607 |
expected |
f62e83484fe30190 |
Vector 3 — DarkCrypt Skipjack vector 3/incr2
| Field | Value |
|---|---|
key |
0102030405060708090a |
input |
1011121314151617 |
expected |
20ab989c85456b03 |
Vector 4 — Bouncy Castle SkipjackTest reference vector
| Field | Value |
|---|---|
key |
00998877665544332211 |
input |
33221100ddccbbaa |
expected |
2587cae27a12d300 |
Vector 5 — LibTomCrypt skipjack.c reference vector (two identical blocks)
| Field | Value |
|---|---|
key |
00998877665544332211 |
input |
33221100ddccbbaa33221100ddccbbaa |
expected |
2587cae27a12d3002587cae27a12d300 |