KDF2
KDF2 Key Derivation Function as defined in IEEE 1363 and ISO/IEC 18033-2. Iterative hash-based KDF using a counter to generate cryptographic keys from shared secrets using optional salt.
Properties
| Property |
Value |
| Category |
Key Derivation Functions |
| Sub-category |
Counter-based KDF |
| Security status |
🎓 Educational Only |
| Complexity |
Intermediate |
| Inventor |
IEEE 1363, ISO/IEC 18033 |
| Year |
2000 |
| Origin |
🇺🇸 United States |
| Source |
algorithms/kdf/kdf2.js |
Parameters
| Parameter |
Supported values |
| Output sizes |
1 byte (8 bits) to 2147483647 bytes (17179869176 bits) |
Capabilities
| Flag |
Value |
SaltRequired |
No |
Security
Status: 🎓 Educational Only
Known vulnerabilities
| Issue |
Description |
Mitigation |
| Hash Function Strength |
KDF2 security depends on the chosen hash function. SHA-1 is considered weak; use SHA-256 or stronger. |
— |
| Counter Overflow |
KDF2 uses 32-bit counter; output limited to 2^32 - 1 hash blocks (approx 16GB for SHA-1) |
— |
| Salt Usage |
Unlike HKDF, KDF2 treats salt as optional input rather than domain separation parameter |
— |
Documentation
References
Test vectors
3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — KDF2(SHA-1) Test Vector 1 - 1 byte output
| Field |
Value |
salt |
bf0b2ecd1724a348211d8c0ca7 |
outputSize |
1 |
hashFunction |
SHA-1 |
input |
fd7a43ea8a443c580c0de618ecc013704505eff8b5a4a9 |
expected |
79 |
Vector 2 — KDF2(SHA-1) Test Vector 2 - 2 byte output
| Field |
Value |
salt |
55a4e9dd5f4ca2ef82 |
outputSize |
2 |
hashFunction |
SHA-1 |
input |
701f3480dfe95f57941f804b1b2413ef |
expected |
fbec |
Vector 3 — KDF2(SHA-1) BouncyCastle Test Vector - full block (no salt)
| Field |
Value |
salt |
(empty) |
outputSize |
20 |
hashFunction |
SHA-1 |
input |
ca7c0f8c3ffa87a96e1b74ac8e6af594347bb40a |
expected |
744ab703f5bc082e59185f6d049d2d367db245c2 |
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