org.spongycastle.crypto.generators

Class KDFCounterBytesGenerator

java.lang.Object

org.spongycastle.crypto.generators.KDFCounterBytesGenerator

All Implemented Interfaces:

DerivationFunction, MacDerivationFunction

public class KDFCounterBytesGenerator
extends java.lang.Object
implements MacDerivationFunction

This KDF has been defined by the publicly available NIST SP 800-108 specification. NIST SP800-108 allows for alternative orderings of the input fields, meaning that the input can be formated in multiple ways. There are 3 supported formats: - Below [i]_2 is a counter of r-bits length concatenated to the fixedInputData.

• 1: K(i) := PRF( KI, [i]_2 || Label || 0x00 || Context || [L]_2 ) with the counter at the very beginning of the fixedInputData (The default implementation has this format)
• 2: K(i) := PRF( KI, Label || 0x00 || Context || [L]_2 || [i]_2 ) with the counter at the very end of the fixedInputData
• 3a: K(i) := PRF( KI, Label || 0x00 || [i]_2 || Context || [L]_2 ) OR:
• 3b: K(i) := PRF( KI, Label || 0x00 || [i]_2 || [L]_2 || Context ) OR:
• 3c: K(i) := PRF( KI, Label || [i]_2 || 0x00 || Context || [L]_2 ) etc... with the counter somewhere in the 'middle' of the fixedInputData.

This function must be called with the following KDFCounterParameters(): - KI
- The part of the fixedInputData that comes BEFORE the counter OR null
- the part of the fixedInputData that comes AFTER the counter OR null
- the length of the counter in bits (not bytes)

Resulting function calls assuming an 8 bit counter.

• 1. KDFCounterParameters(ki, null, "Label || 0x00 || Context || [L]_2]", 8);
• 2. KDFCounterParameters(ki, "Label || 0x00 || Context || [L]_2]", null, 8);
• 3a. KDFCounterParameters(ki, "Label || 0x00", "Context || [L]_2]", 8);
• 3b. KDFCounterParameters(ki, "Label || 0x00", "[L]_2] || Context", 8);
• 3c. KDFCounterParameters(ki, "Label", "0x00 || Context || [L]_2]", 8);

Constructor Summary

Constructors

Constructor and Description
KDFCounterBytesGenerator(Mac prf)

Method Summary

Modifier and Type	Method and Description
int	generateBytes(byte[] out, int outOff, int len)
Mac	getMac() return the MAC used as the basis for the function
void	init(DerivationParameters param)

Methods inherited from class java.lang.Object

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

Constructor Detail

KDFCounterBytesGenerator

public KDFCounterBytesGenerator(Mac prf)

Method Detail

init

public void init(DerivationParameters param)

Specified by:

init in interface DerivationFunction

getMac

public Mac getMac()

Description copied from interface: MacDerivationFunction

return the MAC used as the basis for the function

Specified by:

getMac in interface MacDerivationFunction

generateBytes

public int generateBytes(byte[] out,
                         int outOff,
                         int len)
                  throws DataLengthException,
                         java.lang.IllegalArgumentException

Specified by:

generateBytes in interface DerivationFunction

Throws:

DataLengthException

java.lang.IllegalArgumentException