public abstract class KeyAgreementSpi extends Object
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.
Constructor | Description |
---|---|
KeyAgreementSpi() |
Constructor for subclasses to call. |
Modifier and Type | Method | Description |
---|---|---|
protected abstract Key |
engineDoPhase |
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. |
protected abstract byte[] |
engineGenerateSecret() |
Generates the shared secret and returns it in a new buffer. |
protected abstract int |
engineGenerateSecret |
Generates the shared secret, and places it into the buffer sharedSecret , beginning at offset inclusive. |
protected abstract SecretKey |
engineGenerateSecret |
Creates the shared secret and returns it as a secret key object of the requested algorithm type. |
protected abstract void |
engineInit |
Initializes this key agreement with the given key and source of randomness. |
protected abstract void |
engineInit |
Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness. |
public KeyAgreementSpi()
protected abstract void engineInit(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 randomnessInvalidKeyException
- if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.protected abstract void engineInit(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 randomnessInvalidKeyException
- 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.protected abstract Key engineDoPhase(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 this is the last phase of this key agreement.null
if this phase does not yield a keyInvalidKeyException
- if the given key is inappropriate for this phase.IllegalStateException
- if this key agreement has not been initialized.protected abstract byte[] engineGenerateSecret() throws IllegalStateException
This method resets this KeyAgreementSpi
object to the state that it was in after the most recent call to one of the init
methods. After a call to generateSecret
, the object can be reused for further key agreement operations by calling doPhase
to supply new keys, and then calling generateSecret
to produce a new secret. In this case, the private information and algorithm parameters supplied to init
will be used for multiple key agreement operations. The init
method can be called after generateSecret
to change the private information used in subsequent operations.
IllegalStateException
- if this key agreement has not been initialized or if doPhase
has not been called to supply the keys for all parties in the agreementprotected abstract int engineGenerateSecret(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 KeyAgreementSpi
object to the state that it was in after the most recent call to one of the init
methods. After a call to generateSecret
, the object can be reused for further key agreement operations by calling doPhase
to supply new keys, and then calling generateSecret
to produce a new secret. In this case, the private information and algorithm parameters supplied to init
will be used for multiple key agreement operations. The init
method can be called after generateSecret
to change the private information used in subsequent operations.
sharedSecret
- the buffer for the shared secretoffset
- the offset in sharedSecret
where the shared secret will be storedsharedSecret
IllegalStateException
- if this key agreement has not been initialized or if doPhase
has not been called to supply the keys for all parties in the agreementShortBufferException
- if the given output buffer is too small to hold the secretprotected abstract SecretKey engineGenerateSecret(String algorithm) throws IllegalStateException, NoSuchAlgorithmException, InvalidKeyException
This method resets this KeyAgreementSpi
object to the state that it was in after the most recent call to one of the init
methods. After a call to generateSecret
, the object can be reused for further key agreement operations by calling doPhase
to supply new keys, and then calling generateSecret
to produce a new secret. In this case, the private information and algorithm parameters supplied to init
will be used for multiple key agreement operations. The init
method can be called after generateSecret
to change the private information used in subsequent operations.
algorithm
- the requested secret key algorithmIllegalStateException
- if this key agreement has not been initialized or if doPhase
has not been called to supply the keys for all parties in the agreementNoSuchAlgorithmException
- if the requested secret key algorithm is not availableInvalidKeyException
- 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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