- java.lang.Object
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- javax.crypto.KeyAgreementSpi
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public abstract class KeyAgreementSpi extends Object
This class defines the Service Provider Interface (SPI) for theKeyAgreement
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
orKeyGenerator
), aKeyFactory
, 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 thelastPhase
flag set totrue
. If the key exchange is with two other parties,engineDoPhase
needs to be called twice, the first time setting thelastPhase
flag tofalse
, and the second time setting it totrue
. There may be any number of parties involved in a key exchange.- Since:
- 1.4
- See Also:
KeyGenerator
,SecretKey
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Constructor Summary
Constructors Constructor and Description KeyAgreementSpi()
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Method Summary
Methods Modifier and Type Method and Description 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.protected abstract byte[]
engineGenerateSecret()
Generates the shared secret and returns it in a new buffer.protected abstract int
engineGenerateSecret(byte[] sharedSecret, int offset)
Generates the shared secret, and places it into the buffersharedSecret
, beginning atoffset
inclusive.protected abstract SecretKey
engineGenerateSecret(String algorithm)
Creates the shared secret and returns it as a secret key object of the requested algorithm type.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.protected abstract void
engineInit(Key key, SecureRandom random)
Initializes this key agreement with the given key and source of randomness.
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Method Detail
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engineInit
protected abstract void engineInit(Key key, SecureRandom random) throws InvalidKeyException
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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engineInit
protected abstract void engineInit(Key key, AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
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 parametersrandom
- 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.
-
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.IllegalStateException
- if this key agreement has not been initialized.
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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 reinitialized with one of theengineInit
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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engineGenerateSecret
protected abstract int engineGenerateSecret(byte[] sharedSecret, int offset) throws IllegalStateException, ShortBufferException
Generates the shared secret, and places it into the buffersharedSecret
, beginning atoffset
inclusive.If the
sharedSecret
buffer is too small to hold the result, aShortBufferException
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 theengineInit
methods, the same private information and algorithm parameters will be used for subsequent key agreements.- Parameters:
sharedSecret
- the buffer for the shared secretoffset
- the offset insharedSecret
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 yetShortBufferException
- if the given output buffer is too small to hold the secret
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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 reinitialized with one of theengineInit
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 yetNoSuchAlgorithmException
- 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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