com.google.crypto.tink

Class Key

java.lang.Object

com.google.crypto.tink.Key

Direct Known Subclasses:

AeadKey, LegacyProtoKey, MacKey, PrfKey, SignaturePrivateKey, SignaturePublicKey

@Immutable
 @Alpha
public abstract class Key
extends Object

Represents a cryptographic object.

In Tink, Key objects are objects which represent some cryptographic functions. For example, a MacKey represents the two functions computeMac and verifyMac. The function computeMac maps a byte sequence (possibly with additional randomness) to another byte sequence, called the tag. The function verifyMac verifies the tag. A subclass HmacKey then contains all the information one needs to properly compute an HMAC (including e.g. the hash function and tag length used).

Key objects are light weight, i.e., they should have almost no dependencies, except what is needed to represent the function. This allows key objects to be used in contexts where dependencies need to be kept at a minimum.

Constructor Summary

Constructors

Constructor and Description
Key()

Method Summary

Modifier and Type	Method and Description
abstract boolean	equalsKey(Key other) Returns true if the key is equal to the passed in key.
abstract Integer	getIdRequirementOrNull() Returns null if this key has no id requirement, otherwise the required id.
abstract Parameters	getParameters() Returns a Parameters object containing all the information about the key which is not randomly chosen.

Methods inherited from class java.lang.Object

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

Constructor Detail

Key

public Key()

Method Detail

getParameters

public abstract Parameters getParameters()

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.

getIdRequirementOrNull

@Nullable
public abstract Integer getIdRequirementOrNull()

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.

equalsKey

public abstract boolean equalsKey(Key other)

Returns true if the key is equal to the passed in key.

Implementations are required to do this in constant time.

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