| java.lang.Object | |
| ↳ | javax.crypto.KeyAgreementSpi |
 Known Direct Subclasses
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Class Overview
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
(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
Summary
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| Protected Methods | |||||||||||
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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.
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Generates the shared secret, and places it into the buffer
sharedSecret, beginning at offset inclusive. | |||||||||||
Generates the shared secret and returns it in a new buffer.
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Creates the shared secret and returns it as a secret key object
of the requested algorithm type.
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Initializes this key agreement with the given key and source of
randomness.
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Initializes this key agreement with the given key, set of
algorithm parameters, and source of randomness.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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Public Constructors
public KeyAgreementSpi ()
Protected Methods
protected abstract Key engineDoPhase (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.
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. |
|---|---|
| IllegalStateException | if this key agreement has not been initialized. |
protected abstract int engineGenerateSecret (byte[] sharedSecret, int offset)
Generates the shared secret, and places it into the buffer
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 KeyAgreementSpi object,
so that it
can be reused for further key agreements. Unless this key agreement is
reinitialized 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 |
|---|---|
| ShortBufferException | if the given output buffer is too small to hold the secret |
protected abstract byte[] engineGenerateSecret ()
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
reinitialized 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 |
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protected abstract SecretKey engineGenerateSecret (String algorithm)
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
reinitialized 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 |
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Returns
- the shared secret key
Throws
| IllegalStateException | if this key agreement has not been completed yet |
|---|---|
| NoSuchAlgorithmException | if the requested secret key algorithm is not available |
| 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) |
protected abstract void engineInit (Key key, SecureRandom random)
Initializes 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. |
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protected abstract void engineInit (Key key, AlgorithmParameterSpec params, SecureRandom random)
Initializes 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. |
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| InvalidAlgorithmParameterException | if the given parameters are inappropriate for this key agreement. |