de.flexiprovider.ec
Class ECSVDPDHC

java.lang.Object
  |
  +--javax.crypto.KeyAgreementSpi
        |
        +--de.flexiprovider.api.KeyAgreement
              |
              +--de.flexiprovider.ec.ECSVDPDHC

Direct Known Subclasses:

ECSVDPDH

public class ECSVDPDHC

extends KeyAgreement

ECSVDPDHC provides the implementation for key exchange with the Diffie Hellman algorithm on elliptic curves GP(p), where p is an odd prime number.

This class implements the ECSVDP-DHC primitive from IEEE 1363, i.e. the Diffie Hellman algorithm with co-factor multiplication.

Usage:

kagA and kagB represent the parties trying to establish a shared secret key, each with a private and public key. The following steps have to be performed:

 KeyAgreement kagA = KeyAgreement.getInstance("ECDH", "FlexiEC");
 kagA.init(ecprivA, params, random);
 KeyAgreement kagB = KeyAgreement.getInstance("ECDH", "FlexiEC");
 kagB.init(ecprivB, random);
 ECSecretKey secrA = (ECSecretKey) kagA.doPhase(ecpubB, true);
 ECSecretKey secrB = (ECSecretKey) kagB.doPhase(ecpubA, true);
 

Author:

Jochen Hechler, Marcus Stögbauer, Martin Döring

See Also:

ECPrivateKey, ECPublicKey, ECSecretKey

Field Summary

protected boolean

withCoFactor flag indicating whether cofactor multiplication shall be used

Constructor Summary

ECSVDPDHC()

Method Summary

Key	doPhase(PublicKey key, boolean lastPhase) Executes the next phase of this key agreement with the given key that was received from one of the other parties involved in this key agreement.
byte[]	generateSecret() Generates the shared Secret and returns it as an byte-array.
int	generateSecret(byte[] sharedSecret, int offset) Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset inclusive.
SecretKey	generateSecret(java.lang.String algorithm) Generate the shared secret via the algorithm specified in algorithm.
void	init(PrivateKey key, AlgorithmParameterSpec params, SecureRandom random) Initializes this ECSVDPDHC with a key, the curve parameters and some random information which is not being used here.
void	init(PrivateKey key, SecureRandom random) Initializes this ECSVDPDHC with a key and some random information which is not being used here.

Methods inherited from class de.flexiprovider.api.KeyAgreement

engineDoPhase, engineGenerateSecret, engineGenerateSecret, engineGenerateSecret, engineInit, engineInit

Methods inherited from class java.lang.Object

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

Field Detail

withCoFactor

protected boolean withCoFactor

flag indicating whether cofactor multiplication shall be used

Constructor Detail

ECSVDPDHC

public ECSVDPDHC()

Method Detail

init

public void init(PrivateKey key,
                 AlgorithmParameterSpec params,
                 SecureRandom random)
          throws InvalidKeyException

Initializes this ECSVDPDHC with a key, the curve parameters and some random information which is not being used here.

Overrides:

init in class KeyAgreement

Parameters:

key - is the private key of the party initializing ECSVDPDHC

params - are the curve parameters

random - contains some random information that are randomly ignored

Throws:

InvalidKeyException - if key is no instance of ECPrivateKey.

init

public void init(PrivateKey key,
                 SecureRandom random)
          throws InvalidKeyException

Initializes this ECSVDPDHC with a key and some random information which is not being used here.

Parameters:

key - is the secret key of the party initializing ECSVDPDHC

random - contains some random information that are randomly ignored

Throws:

InvalidKeyException - if key is no instance of ECPrivateKey

generateSecret

public SecretKey generateSecret(java.lang.String algorithm)
                         throws NoSuchAlgorithmException

Generate the shared secret via the algorithm specified in algorithm. Only ECDH is valid for algorithm. This is only a wrapper function, the whole work is done in secretGenerator.

Overrides:

generateSecret in class KeyAgreement

Parameters:

algorithm - is the desired algorithm for the generation of the secret

Returns:

the shared secret as an SecretKey

Throws:

NoSuchAlgorithmException - if algorithm isn't ECDH

generateSecret

public int generateSecret(byte[] sharedSecret,
                          int offset)
                   throws ShortBufferException

Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset inclusive. This is only a wrapper function, the whole work is done in secretGenerator.

Overrides:

generateSecret in class KeyAgreement

Parameters:

sharedSecret - is the buffer for the shared secret

offset - is the offset in sharedSecret where the shared secret will be stored

Returns:

the number of bytes written in sharedSecret

Throws:

ShortBufferException - if sharedSecret is too small to to hold the shared secret

generateSecret

public byte[] generateSecret()

Generates the shared Secret and returns it as an byte-array. This is only a wrapper function, the whole work is done in secretGenerator.

Overrides:

generateSecret in class KeyAgreement

Returns:

the shared SecretValue as an byte-array, and null if the object is not in DoPhase

doPhase

public Key doPhase(PublicKey key,
                   boolean lastPhase)
            throws InvalidKeyException

Executes the next phase of this key agreement with the given key that was received from one of the other parties involved in this key agreement.

Overrides:

doPhase in class KeyAgreement

Parameters:

key - the public key of the other party

lastPhase - true, if this is the last phase of the key agreement. After the last phase only generateSecret should be called.

Returns:

the shared secret as a java.security.Key

Throws:

InvalidKeyException - if key is no interface of an ECPublicKey or if key is an invalid ECPublicKey