GordianKnot Macs

Overview

MACs are supported via the GordianMacFactory interface.

GordianKnot supports most Macs available from BouncyCastle plus some additional algorithms.

JCA provides a subset of available algorithms as indicated

Macs

A mac is created by specifying a macSpec which comprises the macType plus additional configuration (e.g. digestSpec/symKeySpec) as appropriate. The mac can be used in much the same way as a JCA Mac, allowing init, reset, update and finalise methods.

A keyGenerator for a macSpec can be created, which can be used to generate random keys for the mac

Sample

/* Access factory */
final GordianFactory myBaseFactory = GordianGenerator.createFactory();
final GordianMacFactory myMacFactory = myBaseFactory.getMacFactory();

/* Create mac */
final GordianMacSpec mySpec = GordianMacSpecBuilder.poly1305(GordianSymKeySpec.aes(GordianLength.LEN_256));
final GordianMac myMac = myMacFactory.createMac(mySpec);

/* Create key */
final GordianKeyGenerator<GordianMacSpec> myGenerator = myMacFactory.getKeyGenerator(mySpec);
final GordianKey<GordianMacSpec> myKey = myGenerator.generateKey();

/* Calculate mac */
final byte[] myMessage = ...
final GordianMacParameters myParams = GordianMacParameters.keyWithRandomNonce(myKey);
myMac.init(myParams);
myMac.update(myMessage);
final byte[] myResult = myMac.finish();
                    

Extensible Output functions

Some macs can operate as extensible output functions, although the functionality is not available in JCA.

The **GordianMacSpec** for the mac will indicate whether the mac supports Xof or not via the **isXof()** call. If the mac supports Xof then the mac will present the **GordianXof** interface

Sample

/* Access factory */
final GordianFactory myBaseFactory = GordianGenerator.createFactory();
final GordianMacFactory myMacFactory = myBaseFactory.getMacFactory();

/* Create mac */
final GordianMacSpec mySpec = GordianMacSpecBuilder.blake3Mac(GordianLength.LEN_256);
final GordianMac myMac = myMacFactory.createMac(mySpec);
final GordianXof myXof = (GordianXof) myMac;

/* Create key */
final GordianKeyGenerator<GordianMacSpec> myGenerator = myMacFactory.getKeyGenerator(mySpec);
final GordianKey<GordianMacSpec> myKey = myGenerator.generateKey();

/* Calculate mac */
final byte[] myMessage = ...
final GordianMacParameters myParams = GordianMacParameters.key(myKey);
myMac.init(myParams);
myDigest.update(myMessage);
final byte[] myOutput = new byte[200];
myDigest.output(myOutput, 0, 100);
myDigest.output(myOutput, 100, 100);
                    

Algorithms

The following algorithms are supported, with the JCA subset indicated.