Concat KDF (Hash)
NIST SP 800-56A/C Concatenation Key Derivation Function using hash functions. Official NIST-recommended KDF for key agreement protocols like ECDH. Single-step KDF that concatenates counter, shared secret, and context information.
Properties
| Property |
Value |
| Category |
Key Derivation Functions |
| Sub-category |
Single-Step KDF |
| Security status |
🛡️ Secure |
| Complexity |
Intermediate |
| Inventor |
NIST |
| Year |
2007 |
| Origin |
🇺🇸 United States |
| Source |
algorithms/kdf/concat-kdf.js |
Parameters
| Parameter |
Supported values |
| Output sizes |
1 byte (8 bits) to 65535 bytes (524280 bits) |
Capabilities
| Flag |
Value |
SaltRequired |
No |
Security
Status: 🛡️ Secure
Known vulnerabilities
| Issue |
Description |
Mitigation |
| Weak Hash Function |
Use SHA-256 or SHA-512 instead of SHA-1 for modern security requirements |
— |
| Insufficient Shared Secret Entropy |
Ensure shared secret from key agreement has sufficient entropy for cryptographic security |
— |
| Missing Context Information |
Include appropriate context in otherinfo parameter to bind derived key to specific usage |
— |
Documentation
References
Test vectors
3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — ConcatKDFHash SHA-256 Test Vector
| Field |
Value |
otherinfo |
a1b2c3d4e53728157e634612c12d6d52 23e204aeea4341565369647bd184bcd2 46f72971f292badaa2fe4124612cba |
outputSize |
16 |
hashFunction |
SHA-256 |
input |
52169af5c485dcc2321eb8d26d5efa21fb9b93c98e38412ee2484cf14f0d0d23 |
expected |
1c3bc9e7c4547c5191c0d478cccaed55 |
Vector 2 — NIST SP 800-56A single-step KDF, SHA-256, 33 byte output
| Field |
Value |
otherinfo |
ea0e5d80a76bb5063148cc997b76da2d895bc3e4dff37c48579cc4e580f1fda3 |
outputSize |
33 |
hashFunction |
SHA-256 |
input |
7ce80e8b0480cde01fec587fe7045a8e |
expected |
9e04ddba94c2c36f8e9b1b6f9b0f4d70 a20cf1122dd94ab5724d192ed1939d92 4d |
Vector 3 — NIST SP 800-56A single-step KDF, SHA-256, 48 byte output
| Field |
Value |
otherinfo |
2d14c1c1989469a6676196410b62af1a98d05de226b22213fa731a814ade2f5c |
outputSize |
48 |
hashFunction |
SHA-256 |
input |
8d1c9b4d7cc7f6122cb68e43b146bd32 de9f5e09143118b29db51705f25d6c81 890132f81df3dc53a7950d0803107306 289fa88e907c2e53ec13eca20f972b38 b84c5c1847f0bcb2ee4a9b64eb48348b 73256e61ce2a2cfcdb71f7db70bffcc1 01f8a7f1fee5f9d377e81ff9ec79b7fb 25c849d7b9dd125107717ec8fd931057 62b1ac629ff6df99 |
expected |
95352c138eb9b23735bd68cb24288997 0846dccbd9775bcad068528e8008a3ba f1ed2047525eaa29c99cd6e0e634eb30 |
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