at.favre.lib.crypto

Class HFunction.MessageDigestHFunction

java.lang.Object

at.favre.lib.crypto.HFunction.MessageDigestHFunction

All Implemented Interfaces:

HFunction

Enclosing interface:

HFunction

public static final class HFunction.MessageDigestHFunction
extends Object
implements HFunction

Hash implementation of the H function.

Nested Class Summary

Nested classes/interfaces inherited from interface at.favre.lib.crypto.HFunction

HFunction.MacHFunction, HFunction.MessageDigestHFunction

Constructor Summary

Constructors

Constructor and Description
MessageDigestHFunction(MessageDigest digest)

Method Summary

Modifier and Type	Method and Description
byte[]	calculate() After adding the input through HFunction.update(byte[]) calculate the output of the H-function
int	getHFuncOutputBytes() Formally: a positive integer that indicates the length of the output of the auxiliary function, H, that is used to derive blocks of secret keying material.
void	init(byte[] key) Optional keying of the H function.
boolean	requireInit() If the function requires a key to be provided in the HFunction.init(byte[])
void	reset() Resets the function for further use.
void	update(byte[] array) Update the function with a new input that will internally added to the already available input

Methods inherited from class java.lang.Object

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

Constructor Detail

MessageDigestHFunction

public MessageDigestHFunction(MessageDigest digest)

Method Detail

init

public void init(byte[] key)

Description copied from interface: HFunction

Optional keying of the H function. This is not supported with hash type functions and may throw an UnsupportedOperationException. Call this before HFunction.update(byte[])

Specified by:

init in interface HFunction

Parameters:

key - to be used; if null is passed, default_salt is used, which is in the case of HMAC a empty byte array the length of the underyling hash function (e.g. 32 bytes for SHA-256)

requireInit

public boolean requireInit()

Description copied from interface: HFunction

If the function requires a key to be provided in the HFunction.init(byte[])

Specified by:

requireInit in interface HFunction

Returns:

true if user must initialize with init()

getHFuncOutputBytes

public int getHFuncOutputBytes()

Description copied from interface: HFunction

Formally: a positive integer that indicates the length of the output of the auxiliary function, H, that is used to derive blocks of secret keying material.

The spec describes the length in bits, but for practical reasons it will return bytes.

Practically the length of output hash/hmac/kmac function. E.g. SHA-256 or HMAC_SHA-256 will output 32 byte long block.

Specified by:

getHFuncOutputBytes in interface HFunction

Returns:

output length in byte

update

public void update(byte[] array)

Description copied from interface: HFunction

Update the function with a new input that will internally added to the already available input

Specified by:

update in interface HFunction

Parameters:

array - to process

calculate

public byte[] calculate()

Description copied from interface: HFunction

After adding the input through HFunction.update(byte[]) calculate the output of the H-function

Specified by:

calculate in interface HFunction

Returns:

output (usually a hash)

reset

public void reset()

Description copied from interface: HFunction

Resets the function for further use.

Specified by:

reset in interface HFunction