iaik.security.kdf

Class KDF2

java.lang.Object

javax.crypto.KeyGeneratorSpi

iaik.security.kdf.KDF1

iaik.security.kdf.KDF2

Direct Known Subclasses:

KDF3

public class KDF2
extends KDF1

This class implements the Key Derivation Function (KDF) 2, defined in ISO/IEC 18033-2. A KDF is a function which derives keying material of desired length from a shared secret and additional, optional information. The KDF itself is further parameterized with, e.g., a cryptographic hash function.

An application which wants to use KDF2 has to obtain it via the KeyGenerator engine class.

     KeyGenerator kdf2 = KeyGenerator.getInstance("KDF2", "IAIK");
 

A caller has to configure the KDF2 with a cryptographic hash function, like SHA2-256, SHA3-256,.... For that use KDF2ParameterSpec. An example usage may look like this:

A
     AlgorithmID hashAlg = ...;
     int keyLength = ...;
     byte[] secretValue = ...
     KDF2ParameterSpec spec = new KDF2ParameterSpec(hashAlg, keyLength);
     spec.setSecretValue(secretValue);
     kg.init(spec);
     SecretKey key = (SecretKey) kg.generateKey();
 

If an implementation tries to use the KDF2 without a call to KDF1.engineInit(AlgorithmParameterSpec, SecureRandom), the class will throw an exception.

This class extends KDF1, because of the similarity of their workflow.

See Also:

KDF2ParameterSpec

Field Summary

Fields

Modifier and Type	Field and Description
static ObjectID	OID The ASN.1 object identifier (1.3.133.16.840.9.44.1.1) for the KDF2 key derivation function.

Constructor Summary

Constructors

Constructor and Description
KDF2()

Method Summary

Methods

Modifier and Type	Method and Description
protected javax.crypto.SecretKey	engineGenerateKey() Generates a key according to the specification of KDF2 with the provided information.
protected HashBasedGenerationFunction	generateHBGF(KDF1ParameterSpec spec) Intern helper function to create an instance of HashBasedGenerationFunction.
protected java.lang.String	name() Outputs the algorithm name.

Methods inherited from class iaik.security.kdf.KDF1

engineInit, engineInit, engineInit

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

OID

public static final ObjectID OID

The ASN.1 object identifier (1.3.133.16.840.9.44.1.1) for the KDF2 key derivation function.

Constructor Detail

KDF2

public KDF2()

Method Detail

name

protected java.lang.String name()

Outputs the algorithm name. Will always return "KDF2".

Overrides:

name in class KDF1

Returns:

"KDF2"

generateHBGF

protected HashBasedGenerationFunction generateHBGF(KDF1ParameterSpec spec)

Intern helper function to create an instance of HashBasedGenerationFunction. Note: Do not call this on your own.

Overrides:

generateHBGF in class KDF1

engineGenerateKey

protected javax.crypto.SecretKey engineGenerateKey()

Generates a key according to the specification of KDF2 with the provided information. This method returns an instance of SecretKey. To obtain the secret, call SecretKey.getEncoded().

Overrides:

engineGenerateKey in class KDF1

Returns:

an instance of SecretKey holding the derived secret.

Throws:

InternalErrorException - if the caller did not initialize the object accordingly.