com.google.crypto.tink.prf.internal

Class LegacyFullPrf

java.lang.Object

com.google.crypto.tink.prf.internal.LegacyFullPrf

All Implemented Interfaces:

Prf

@Immutable
public class LegacyFullPrf
extends Object
implements Prf

Takes an arbitrary raw Prf and makes it a full primitive. ("Full" doesn't make much difference in case of PRFs but we keep the name for consistency with the other primitives.) This is a class that helps us transition onto the new Keys and Configurations interface, by bringing potential user-defined primitives to a common denominator with our primitives over which we have control.

Method Summary

Modifier and Type	Method and Description
byte[]	compute(byte[] input, int outputLength) Computes the PRF selected by the underlying key on input and returns the first outputLength bytes.
static Prf	create(LegacyProtoKey key) This method covers the cases where users created their own prf/key classes.

Methods inherited from class java.lang.Object

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

Method Detail

create

public static Prf create(LegacyProtoKey key)
                  throws GeneralSecurityException

This method covers the cases where users created their own prf/key classes.

Throws:

GeneralSecurityException

compute

public byte[] compute(byte[] input,
                      int outputLength)
               throws GeneralSecurityException

Description copied from interface: Prf

Computes the PRF selected by the underlying key on input and returns the first outputLength bytes.

Specified by:

compute in interface Prf

Parameters:

input - the input to compute the PRF on.

outputLength - the desired length of the output in bytes. When choosing this parameter keep the birthday paradox in mind. If you have 2^n different inputs that your system has to handle set the output length to ceil(n/4 + 4) This corresponds to 2*n + 32 bits, meaning a collision will occur with a probability less than 1:2^32. When in doubt, request a security review.

Throws:

GeneralSecurityException - if the algorithm fails or if the output of algorithm is less than outputLength.