Class KDF

java.lang.Object
javax.crypto.KDF
public final class KDF extends Object
KDF is a preview API of the Java platform.
Programs can only use KDF when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
This class provides the functionality of a Key Derivation Function (KDF), which is a cryptographic algorithm for deriving additional keys from input keying material (IKM) and (optionally) other data.

KDF objects are instantiated with the getInstance family of methods.

The class has two derive methods, deriveKey and deriveData. The deriveKey method accepts an algorithm name and returns a SecretKey object with the specified algorithm. The deriveData method returns a byte array of raw data.

API Usage Example: 

    KDF kdfHkdf = KDF.getInstance("HKDF-SHA256");

    AlgorithmParameterSpec derivationSpec =
             HKDFParameterSpec.ofExtract()
                              .addIKM(ikm)
                              .addSalt(salt).thenExpand(info, 32);

    SecretKey sKey = kdfHkdf.deriveKey("AES", derivationSpec);

Concurrent Access

Unless otherwise documented by an implementation, the methods defined in this class are not thread-safe. Multiple threads that need to access a single object concurrently should synchronize amongst themselves and provide the necessary locking. Multiple threads each manipulating separate objects need not synchronize.

Delayed Provider Selection

If a provider is not specified when calling one of the getInstance methods, the implementation delays the selection of the provider until the deriveKey or deriveData method is called. This is called delayed provider selection. The primary reason this is done is to ensure that the selected provider can handle the key material that is passed to those methods - for example, the key material may reside on a hardware device that only a specific KDF provider can utilize. The getInstance method returns a KDF object as long as there exists at least one registered security provider that implements the algorithm and supports the optional parameters. The delayed provider selection process traverses the list of registered security providers, starting with the most preferred Provider. The first provider that supports the specified algorithm, optional parameters, and key material is selected.

If the getProviderName or getParameters method is called before the deriveKey or deriveData methods, the first provider supporting the KDF algorithm and optional KDFParameters is chosen. This provider may not support the key material that is subsequently passed to the deriveKey or deriveData methods. Therefore, it is recommended not to call the getProviderName or getParameters methods until after a key derivation operation. Once a provider is selected, it cannot be changed.

Since:
24
See Also: