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Class javax.crypto.KeyAgreementSpi
java.lang.Object
|
+----javax.crypto.KeyAgreementSpi
- public abstract class KeyAgreementSpi
- extends Object
This class defines the Service Provider Interface (SPI) for the KeyAgreement
class. All the abstract methods in this class must be implemented by each
cryptographic service provider who wishes to supply the implementation of a
particular key agreement algorithm.
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
engineDoPhase).
For each of the correspondents in the key exchange, engineDoPhase needs to
be called. For example, if the key exchange is with one other party,
engineDoPhase needs to be called once, with the lastPhase flag set to true.
If the key exchange is with two other parties, engineDoPhase 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.
- See Also:
- KeyGenerator, SecretKey
-
KeyAgreementSpi()
- Default constructor for KeyAgreementSpi, must be public.
-
engineDoPhase(Key, boolean)
- 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.
-
engineGenerateSecret()
- Generates the shared secret and returns it in a new buffer.
-
engineGenerateSecret(byte[], int)
- Generates the shared secret, and places it into the buffer
sharedSecret, beginning at offset.
-
engineGenerateSecret(String)
- Creates the shared secret and returns it as a secret key object of
the requested algorithm type.
-
engineInit(Key, AlgorithmParameterSpec, SecureRandom)
- Initialises this key agreement with the given key, set of algorithm
parameters, and source of randomness.
-
engineInit(Key, SecureRandom)
- Initialises this key agreement with the given key and source of
randomness.
KeyAgreementSpi
public KeyAgreementSpi()
- Default constructor for KeyAgreementSpi, must be public.
engineInit
protected abstract void engineInit(Key key,
SecureRandom random) throws InvalidKeyException
- Initialises this key agreement with the given key and source of
randomness. The given key is required to contain all the algorithm
parameters required for this key agreement.
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.
- Parameters:
- 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.
- Throws: InvalidKeyException
- if the given key is inappropriate for
this key agreement, e.g., is of the wrong type or has an
incompatible algorithm type.
engineInit
protected abstract void engineInit(Key key,
AlgorithmParameterSpec params,
SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
- Initialises this key agreement with the given key, set of algorithm
parameters, and source of randomness.
- Parameters:
- 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
- random - the source of randomness
- Throws: InvalidKeyException
- if the given key is inappropriate for
this key agreement, e.g., is of the wrong type or has an
incompatible algorithm type.
- Throws: InvalidAlgorithmParameterException
- if the given parameters
are inappropriate for this key agreement.
engineDoPhase
protected abstract Key engineDoPhase(Key key,
boolean lastPhase) throws InvalidKeyException, IllegalStateException
- 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.
- Parameters:
- 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.
- Returns:
- the (intermediate) key resulting from this phase, or null if
this phase does not yield a key
- Throws: InvalidKeyException
- if the given key is inappropriate for
this phase.
- Throws: IllegalStateException
- if this key agreement has not been
initialised.
engineGenerateSecret
protected abstract byte[] engineGenerateSecret() throws IllegalStateException
- Generates the shared secret and returns it in a new buffer.
This method resets this KeyAgreementSpi object, so that it can be
reused for further key agreements. Unless this key agreement is
reinitialised with one of the engineInit methods, the same private
information and algorithm parameters will be used for subsequent key
agreements.
- Returns:
- the new buffer with the shared secret
- Throws: IllegalStateException
- if this key agreement has not been
completed yet
engineGenerateSecret
protected abstract int engineGenerateSecret(byte sharedSecret[],
int offset) throws IllegalStateException, ShortBufferException
- Generates the shared secret, and places it into the buffer
sharedSecret, beginning at offset.
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 KeyAgreementSpi object, so that it can be
reused for further key agreements. Unless this key agreement is
reinitialised with one of the engineInit methods, the same private
information and algorithm parameters will be used for subsequent key
agreements.
- Parameters:
- sharedSecret - the buffer for the shared secret
- offset - the offset in sharedSecret where the shared secret
will be stored
- Returns:
- the number of bytes placed into sharedSecret
- Throws: IllegalStateException
- if this key agreement has not been
completed yet
- Throws: ShortBufferException
- if the given output buffer is too
small to hold the secret
engineGenerateSecret
protected abstract SecretKey engineGenerateSecret(String algorithm) throws IllegalStateException, NoSuchAlgorithmException, InvalidKeyException
- Creates the shared secret and returns it as a secret key object of
the requested algorithm type.
This method resets this KeyAgreementSpi object, so that it can be
reused for further key agreements. Unless this key agreement is
reinitialised with one of the engineInit methods, the same private
information and algorithm parameters will be used for subsequent key
agreements.
- Parameters:
- algorithm - the requested secret key algorithm
- Returns:
- the shared secret key
- Throws: IllegalStateException
- if this key agreement has not been
completed yet
- Throws: NoSuchAlgorithmException
- if the requested secret key
algorithm is not available
- Throws: InvalidKeyException
- if the shared secret key material
cannot be used to generate a secret key of the requested algorithm
type (e.g., the key material is too short)
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