public class ECDHKeyAgreement extends KeyAgreementSpi
The value produced by engineGenerateSecret() and its overloads is the raw ECDH shared secret (the X
coordinate of the agreed point). As required by NIST SP 800-56A, this raw value is not uniformly random and
must not be used directly as a symmetric key: callers must derive the actual key material by passing
the shared secret through a key-derivation function (for example HKDF or ANSI X9.63) before using it with a cipher or
a MAC.
| Constructor and Description |
|---|
ECDHKeyAgreement() |
| Modifier and Type | Method and Description |
|---|---|
protected 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 byte[] |
engineGenerateSecret()
Generates the shared secret and returns it in a new buffer.
|
protected int |
engineGenerateSecret(byte[] sharedSecret,
int offset)
Generates the shared secret, and places it into the buffer
sharedSecret, beginning at offset inclusive. |
protected SecretKey |
engineGenerateSecret(String algorithm)
Creates the shared secret and returns it as a secret key object
of the requested algorithm type.
|
protected 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 void |
engineInit(Key key,
SecureRandom random)
Initializes this key agreement with the given key and source of
randomness.
|
public ECDHKeyAgreement()
throws NoSuchAlgorithmException
NoSuchAlgorithmException@Nullable protected Key engineDoPhase(Key key, boolean lastPhase) throws InvalidKeyException, IllegalStateException
KeyAgreementSpiengineDoPhase in class KeyAgreementSpikey - 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.InvalidKeyException - if the given key is inappropriate for
this phase.IllegalStateException - if this key agreement has not been
initialized.protected byte[] engineGenerateSecret()
throws IllegalStateException
KeyAgreementSpiThis 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.
engineGenerateSecret in class KeyAgreementSpiIllegalStateException - if this key agreement has not been
completed yetprotected int engineGenerateSecret(byte[] sharedSecret,
int offset)
throws IllegalStateException,
ShortBufferException
KeyAgreementSpisharedSecret, 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.
engineGenerateSecret in class KeyAgreementSpisharedSecret - the buffer for the shared secretoffset - the offset in sharedSecret where the
shared secret will be storedsharedSecretIllegalStateException - if this key agreement has not been
completed yetShortBufferException - if the given output buffer is too small
to hold the secretprotected SecretKey engineGenerateSecret(String algorithm) throws IllegalStateException, NoSuchAlgorithmException, InvalidKeyException
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.
The returned key wraps the raw ECDH shared secret without any key derivation; see the class documentation for why this value must be run through a KDF before it is used as a symmetric key.
engineGenerateSecret in class KeyAgreementSpialgorithm - the requested secret key algorithmIllegalStateException - 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)protected void engineInit(Key key, @Nullable AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
KeyAgreementSpiengineInit in class KeyAgreementSpikey - 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 void engineInit(Key key, SecureRandom random) throws InvalidKeyException
KeyAgreementSpi 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.
engineInit in class KeyAgreementSpikey - 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.