public
abstract
class
KeyAgreementSpi
extends Object
| java.lang.Object | |
| ↳ | javax.crypto.KeyAgreementSpi |
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:
Public constructors | |
|---|---|
KeyAgreementSpi()
|
|
Protected methods | |
|---|---|
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. |
abstract
byte[]
|
engineGenerateSecret()
Generates the shared secret and returns it in a new buffer. |
abstract
SecretKey
|
engineGenerateSecret(String algorithm)
Creates the shared secret and returns it as a secret key object of the requested algorithm type. |
abstract
int
|
engineGenerateSecret(byte[] sharedSecret, int offset)
Generates the shared secret, and places it into the buffer
|
abstract
void
|
engineInit(Key key, SecureRandom random)
Initializes this key agreement with the given key and source of randomness. |
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. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
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 |
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 |
boolean:
flag which indicates whether or not this is the last
phase of this key agreement. |
| Returns | |
|---|---|
Key |
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. |
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 | |
|---|---|
byte[] |
the new buffer with the shared secret |
| Throws | |
|---|---|
IllegalStateException |
if this key agreement has not been completed yet |
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 |
String:
the requested secret key algorithm |
| Returns | |
|---|---|
SecretKey |
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) |
Developers
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 |
byte:
the buffer for the shared secret |
offset |
int:
the offset in sharedSecret where the
shared secret will be stored |
| Returns | |
|---|---|
int |
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 |
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 |
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 |
SecureRandom:
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. |
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 |
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 |
AlgorithmParameterSpec:
the key agreement parameters |
random |
SecureRandom:
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. |
InvalidAlgorithmParameterException |
if the given parameters are inappropriate for this key agreement. |