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java.lang.Objectjavax.crypto.KeyAgreement
public class 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
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,
Provider provider,
String algorithm)
Creates a KeyAgreement object. |
Method Summary | |
---|---|
Key |
doPhase(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(String algorithm)
Creates the shared secret and returns it as a SecretKey
object of the specified algorithm. |
String |
getAlgorithm()
Returns the algorithm name of this KeyAgreement
object. |
static KeyAgreement |
getInstance(String algorithm)
Generates a KeyAgreement object that implements the
specified key agreement algorithm. |
static KeyAgreement |
getInstance(String algorithm,
Provider provider)
Generates a KeyAgreement object for the specified key
agreement algorithm from the specified provider. |
static KeyAgreement |
getInstance(String algorithm,
String provider)
Generates a KeyAgreement object for the specified key
agreement algorithm from the specified provider. |
Provider |
getProvider()
Returns the provider of this KeyAgreement object. |
void |
init(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(Key key,
AlgorithmParameterSpec params)
Initializes this key agreement with the given key and set of algorithm parameters. |
void |
init(Key key,
AlgorithmParameterSpec params,
SecureRandom random)
Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness. |
void |
init(Key key,
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,
Provider provider,
String algorithm)
keyAgreeSpi
- the delegateprovider
- the provideralgorithm
- the algorithmMethod Detail |
---|
public final 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(String algorithm)
throws 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 Reference Guide for information
about standard algorithm names.
KeyAgreement
object
NullPointerException
- if the specified algorithm is null.
NoSuchAlgorithmException
- if the specified algorithm is not available in the default provider
package or any of the other provider packages that were searched.public static final KeyAgreement getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException,
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 Reference Guide for information
about standard algorithm names.provider
- the name of the
provider
KeyAgreement
object
NullPointerException
- if the specified algorithm is null.
NoSuchAlgorithmException
- if the specified algorithm is not available from the specified
provider.
NoSuchProviderException
- if the specified provider has not been configured.
IllegalArgumentException
- if the provider
is null.public static final KeyAgreement getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
KeyAgreement
object
for the specified key agreement algorithm from the specified provider.
Note: the provider
doesn't have to be
registered.
algorithm
- the standard name
of the requested key agreement algorithm. See Appendix A in the
Java Cryptography Extension Reference Guide for information
about standard algorithm names.provider
- the provider
KeyAgreement
object
NullPointerException
- if the specified algorithm is null.
NoSuchAlgorithmException
- if the specified algorithm is not available from the specified
provider.
IllegalArgumentException
- if the provider
is null.public final Provider getProvider()
KeyAgreement
object.
KeyAgreement
objectpublic final void init(Key key)
throws InvalidKeyException
If this key agreement requires any random bytes, it will
get them using the
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.)
SecureRandom
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.
InvalidKeyException
- if the given key is inappropriate for this key agreement, e.g., is of
the wrong type or has an incompatible algorithm type.public final void init(Key key,
SecureRandom random)
throws 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
randomness
InvalidKeyException
- if the given key is inappropriate for this key agreement, e.g., is of
the wrong type or has an incompatible algorithm type.public final void init(Key key,
AlgorithmParameterSpec params)
throws InvalidKeyException,
InvalidAlgorithmParameterException
If this key agreement requires any random bytes, it will
get them using the
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.)
SecureRandom
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
parameters
InvalidKeyException
- if the given key is inappropriate for this key agreement, e.g., is of
the wrong type or has an incompatible algorithm type.
InvalidAlgorithmParameterException
- if the given parameters are inappropriate for this key agreement.public final void init(Key key,
AlgorithmParameterSpec params,
SecureRandom random)
throws InvalidKeyException,
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
randomness
InvalidKeyException
- if the given key is inappropriate for this key agreement, e.g., is of
the wrong type or has an incompatible algorithm type.
InvalidAlgorithmParameterException
- if the given parameters are inappropriate for this key agreement.public final Key doPhase(Key key,
boolean lastPhase)
throws InvalidKeyException,
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.
InvalidKeyException
- if the given key is inappropriate for this phase.
IllegalStateException
- if this key agreement has not been initialized.public final byte[] generateSecret()
throws 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.
IllegalStateException
- if this key agreement has not been completed yetpublic final int generateSecret(byte[] sharedSecret,
int offset)
throws 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 stored
sharedSecret
IllegalStateException
- if this key agreement has not been completed yet
ShortBufferException
- if the given output buffer is too small to hold the secretpublic final SecretKey generateSecret(String algorithm)
throws IllegalStateException,
NoSuchAlgorithmException,
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
IllegalStateException
- if this key agreement has not been completed yet
NoSuchAlgorithmException
- if the specified secret-key algorithm is not available
InvalidKeyException
- if the shared secret-key material cannot be used to generate a secret
key of the specified algorithm (e.g., the key material is too short)
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