com.google.crypto.tink.keyderivation

Class PrfBasedKeyDerivationKey

java.lang.Object

com.google.crypto.tink.Key

com.google.crypto.tink.keyderivation.KeyDerivationKey

com.google.crypto.tink.keyderivation.PrfBasedKeyDerivationKey

public final class PrfBasedKeyDerivationKey
extends KeyDerivationKey

Represents a Derivation key which is based on a PRF.

An object of this class represents the map which 1) uses the given PRF (as specified by getPrfKey()) to get sufficient key material from the salt, then 2) creates a key for the parameters as specified in getParameters().getDerivedKeyParameters().

Method Summary

Modifier and Type	Method and Description
static PrfBasedKeyDerivationKey	create(PrfBasedKeyDerivationParameters parameters, PrfKey prfKey, Integer idRequirement)
boolean	equalsKey(Key other) Returns true if the key is guaranteed to be equal to other.
Integer	getIdRequirementOrNull() Returns null if this key has no id requirement, otherwise the required id.
PrfBasedKeyDerivationParameters	getParameters() Returns a Parameters object containing all the information about the key which is not randomly chosen.
PrfKey	getPrfKey()

Methods inherited from class java.lang.Object

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

Method Detail

create

public static PrfBasedKeyDerivationKey create(PrfBasedKeyDerivationParameters parameters,
                                              PrfKey prfKey,
                                              @Nullable
                                              Integer idRequirement)
                                       throws GeneralSecurityException

Throws:

GeneralSecurityException

getPrfKey

public PrfKey getPrfKey()

getParameters

public PrfBasedKeyDerivationParameters getParameters()

Description copied from class: Key

Returns a Parameters object containing all the information about the key which is not randomly chosen.

Implementations need to ensure that getParameters().hasIdRequirement() returns true if and only if getIdRequirementOrNull is non-null.

Specified by:

getParameters in class KeyDerivationKey

getIdRequirementOrNull

@Nullable
public Integer getIdRequirementOrNull()

Description copied from class: Key

Returns null if this key has no id requirement, otherwise the required id.

Some keys, when they are in a keyset, are required to have a certain ID to work properly. This comes from the fact that Tink in some cases prefixes ciphertexts or signatures with the string 0x01<id>, where the ID is encoded in big endian (see the documentation of the key type for details), in which case the key requires a certain ID.

Specified by:

getIdRequirementOrNull in class Key

equalsKey

public boolean equalsKey(Key other)

Description copied from class: Key

Returns true if the key is guaranteed to be equal to other.

Implementations are required to do this in constant time.

Note: this is allowed to return false even if two keys are guaranteed to represent the same function, but are represented differently. For example, a key is allowed to internally store the number of zero-bytes used as padding when a large number is represented as a byte array, and use this in the comparison.

Note: Tink Key objects should typically not override hashCode (because it could risk leaking key material). Hence, they typically also should not override equals.

Specified by:

equalsKey in class Key