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java.lang.Object | +--javax.crypto.KeyAgreement
This class provides the functionality of a key agreement (or key
exchange) protocol.
The keys involved in establishing a shared secret are created by one of the
key generators (KeyPairGenerator
or
KeyGenerator
), a KeyFactory
, or as a result from
an intermediate phase of the key agreement protocol
(see doPhase).
For each of the correspondents in the key exchange, doPhase
needs to be called. For example, if this key exchange is with one other
party, doPhase
needs to be called once, with the
lastPhase
flag set to true
.
If this key exchange is
with two other parties, doPhase
needs to be called twice,
the first time setting the lastPhase
flag to
false
, and the second time setting it to true
.
There may be any number of parties involved in a key exchange.
KeyGenerator
,
SecretKey
Constructor Summary | |
protected |
KeyAgreement(KeyAgreementSpi keyAgreeSpi,
java.security.Provider provider,
java.lang.String algorithm)
Creates a KeyAgreement object. |
Method Summary | |
java.security.Key |
doPhase(java.security.Key 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 in a new buffer. |
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)
Creates the shared secret and returns it as a SecretKey
object of the specified algorithm. |
java.lang.String |
getAlgorithm()
Returns the algorithm name of this KeyAgreement object. |
static KeyAgreement |
getInstance(java.lang.String algorithm)
Generates a KeyAgreement object that implements the
specified key agreement algorithm. |
static KeyAgreement |
getInstance(java.lang.String algorithm,
java.lang.String provider)
Generates a KeyAgreement object for the specified key
agreement algorithm from the specified provider. |
java.security.Provider |
getProvider()
Returns the provider of this KeyAgreement object. |
void |
init(java.security.Key key)
Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement. |
void |
init(java.security.Key key,
java.security.spec.AlgorithmParameterSpec params)
Initializes this key agreement with the given key and set of algorithm parameters. |
void |
init(java.security.Key key,
java.security.spec.AlgorithmParameterSpec params,
java.security.SecureRandom random)
Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness. |
void |
init(java.security.Key key,
java.security.SecureRandom random)
Initializes this key agreement with the given key and source of randomness. |
Methods inherited from class java.lang.Object |
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait |
Constructor Detail |
protected KeyAgreement(KeyAgreementSpi keyAgreeSpi, java.security.Provider provider, java.lang.String algorithm)
keyAgreeSpi
- the delegateprovider
- the provideralgorithm
- the algorithmMethod Detail |
public final java.lang.String getAlgorithm()
KeyAgreement
object.
This is the same name that was specified in one of the
getInstance
calls that created this
KeyAgreement
object.
KeyAgreement
object.public static final KeyAgreement getInstance(java.lang.String algorithm) throws java.security.NoSuchAlgorithmException
KeyAgreement
object that implements the
specified key agreement algorithm.
If the default provider package provides an implementation of the
requested key agreement algorithm, an instance of
KeyAgreement
containing that implementation is returned.
If the algorithm is not available in the default provider package,
other provider packages are searched.algorithm
- the standard name of the requested key agreement
algorithm.
See Appendix A in the
Java Cryptography Extension API Specification & Reference
for information about standard algorithm names.KeyAgreement
objectpublic static final KeyAgreement getInstance(java.lang.String algorithm, java.lang.String provider) throws java.security.NoSuchAlgorithmException, java.security.NoSuchProviderException
KeyAgreement
object for the specified key
agreement algorithm from the specified provider.algorithm
- the standard name of the requested key agreement
algorithm.
See Appendix A in the
Java Cryptography Extension API Specification & Reference
for information about standard algorithm names.provider
- the name of the providerKeyAgreement
objectpublic final java.security.Provider getProvider()
KeyAgreement
object.KeyAgreement
objectpublic final void init(java.security.Key key) throws java.security.InvalidKeyException
If this key agreement requires any random bytes, it will get
them using the
SecureRandom
implementation of the highest-priority
installed provider as the source of randomness.
(If none of the installed providers supply an implementation of
SecureRandom, a system-provided source of randomness will be used.)
key
- the party's private information. For example, in the case
of the Diffie-Hellman key agreement, this would be the party's own
Diffie-Hellman private key.public final void init(java.security.Key key, java.security.SecureRandom random) throws java.security.InvalidKeyException
If the key agreement algorithm requires random bytes, it gets them
from the given source of randomness, random
.
However, if the underlying
algorithm implementation does not require any random bytes,
random
is ignored.
key
- the party's private information. For example, in the case
of the Diffie-Hellman key agreement, this would be the party's own
Diffie-Hellman private key.random
- the source of randomnesspublic final void init(java.security.Key key, java.security.spec.AlgorithmParameterSpec params) throws java.security.InvalidKeyException, java.security.InvalidAlgorithmParameterException
If this key agreement requires any random bytes, it will get
them using the
SecureRandom
implementation of the highest-priority
installed provider as the source of randomness.
(If none of the installed providers supply an implementation of
SecureRandom, a system-provided source of randomness will be used.)
key
- the party's private information. For example, in the case
of the Diffie-Hellman key agreement, this would be the party's own
Diffie-Hellman private key.params
- the key agreement parameterspublic final void init(java.security.Key key, java.security.spec.AlgorithmParameterSpec params, java.security.SecureRandom random) throws java.security.InvalidKeyException, java.security.InvalidAlgorithmParameterException
key
- the party's private information. For example, in the case
of the Diffie-Hellman key agreement, this would be the party's own
Diffie-Hellman private key.params
- the key agreement parametersrandom
- the source of randomnesspublic final java.security.Key doPhase(java.security.Key key, boolean lastPhase) throws java.security.InvalidKeyException, java.lang.IllegalStateException
key
- the key for this phase. For example, in the case of
Diffie-Hellman between 2 parties, this would be the other party's
Diffie-Hellman public key.lastPhase
- flag which indicates whether or not this is the last
phase of this key agreement.public final byte[] generateSecret() throws java.lang.IllegalStateException
This method resets this KeyAgreement
object, so that it
can be reused for further key agreements. Unless this key agreement is
reinitialized with one of the init
methods, the same
private information and algorithm parameters will be used for
subsequent key agreements.
public final int generateSecret(byte[] sharedSecret, int offset) throws java.lang.IllegalStateException, ShortBufferException
sharedSecret
, beginning at offset
inclusive.
If the sharedSecret
buffer is too small to hold the
result, a ShortBufferException
is thrown.
In this case, this call should be repeated with a larger output buffer.
This method resets this KeyAgreement
object, so that it
can be reused for further key agreements. Unless this key agreement is
reinitialized with one of the init
methods, the same
private information and algorithm parameters will be used for
subsequent key agreements.
sharedSecret
- the buffer for the shared secretoffset
- the offset in sharedSecret
where the
shared secret will be storedsharedSecret
public final SecretKey generateSecret(java.lang.String algorithm) throws java.lang.IllegalStateException, java.security.NoSuchAlgorithmException, java.security.InvalidKeyException
SecretKey
object of the specified algorithm.
This method resets this KeyAgreement
object, so that it
can be reused for further key agreements. Unless this key agreement is
reinitialized with one of the init
methods, the same
private information and algorithm parameters will be used for
subsequent key agreements.
algorithm
- the requested secret-key algorithm
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