Added in API level 1

KeyAgreement

open class KeyAgreement

kotlin.Any
↳	javax.crypto.KeyAgreement

This class provides the functionality of a key agreement (or key exchange) protocol.

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.

For each of the correspondents in the key exchange, doPhase needs to be called. For example, if this key exchange is with one other party, doPhase needs to be called once, with the lastPhase flag set to true. If this key exchange is with two other parties, doPhase 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.

Android provides the following KeyAgreement algorithms:

Algorithm	Supported API Levels
DH	1+
ECDH	11+
XDH	33+

This algorithm is described in the KeyAgreement section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Summary

Protected constructors
KeyAgreement(keyAgreeSpi: KeyAgreementSpi!, provider: Provider!, algorithm: String!) Creates a KeyAgreement object.

Public methods
Key!	doPhase(key: Key!, lastPhase: Boolean) 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.
ByteArray!	generateSecret() Generates the shared secret and returns it in a new buffer.
Int	generateSecret(sharedSecret: ByteArray!, offset: Int) Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset inclusive.
SecretKey!	generateSecret(algorithm: String!) Creates the shared secret and returns it as a SecretKey object of the specified algorithm.
String!	getAlgorithm() Returns the algorithm name of this KeyAgreement object.
static KeyAgreement!	getInstance(algorithm: String!) Returns a KeyAgreement object that implements the specified key agreement algorithm.
static KeyAgreement!	getInstance(algorithm: String!, provider: String!) Returns a KeyAgreement object that implements the specified key agreement algorithm.
static KeyAgreement!	getInstance(algorithm: String!, provider: Provider!) Returns a KeyAgreement object that implements the specified key agreement algorithm.
Provider!	getProvider() Returns the provider of this KeyAgreement object.
Unit	init(key: Key!) Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement.
Unit	init(key: Key!, random: SecureRandom!) Initializes this key agreement with the given key and source of randomness.
Unit	init(key: Key!, params: AlgorithmParameterSpec!) Initializes this key agreement with the given key and set of algorithm parameters.
Unit	init(key: Key!, params: AlgorithmParameterSpec!, random: SecureRandom!) Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness.

Protected constructors

KeyAgreement

Added in API level 1

protected KeyAgreement(
    keyAgreeSpi: KeyAgreementSpi!, 
    provider: Provider!, 
    algorithm: String!)

Creates a KeyAgreement object.

Parameters
keyAgreeSpi	KeyAgreementSpi!: the delegate
provider	Provider!: the provider
algorithm	String!: the algorithm

Public methods

doPhase

Added in API level 1

fun doPhase(
    key: Key!, 
    lastPhase: Boolean
): Key!

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.

Return
Key!	the (intermediate) key resulting from this phase, or null if this phase does not yield a key

Exceptions
java.security.InvalidKeyException	if the given key is inappropriate for this phase.
java.lang.IllegalStateException	if this key agreement has not been initialized.

generateSecret

Added in API level 1

fun generateSecret(): ByteArray!

Generates the shared secret and returns it in a new buffer.

This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

Return
ByteArray!	the new buffer with the shared secret

Exceptions
java.lang.IllegalStateException	if this key agreement has not been completed yet

generateSecret

Added in API level 1

fun generateSecret(
    sharedSecret: ByteArray!, 
    offset: Int
): Int

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 KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

Parameters
sharedSecret	ByteArray!: the buffer for the shared secret
offset	Int: the offset in sharedSecret where the shared secret will be stored

Return
Int	the number of bytes placed into sharedSecret

Exceptions
java.lang.IllegalStateException	if this key agreement has not been completed yet
javax.crypto.ShortBufferException	if the given output buffer is too small to hold the secret

generateSecret

Added in API level 1

fun generateSecret(algorithm: String!): SecretKey!

Creates the shared secret and returns it as a SecretKey object of the specified algorithm.

This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

Parameters
algorithm	String!: the requested secret-key algorithm

Return
SecretKey!	the shared secret key

Exceptions
java.lang.IllegalStateException	if this key agreement has not been completed yet
java.security.NoSuchAlgorithmException	if the specified secret-key algorithm is not available
java.security.InvalidKeyException	if the shared secret-key material cannot be used to generate a secret key of the specified algorithm (e.g., the key material is too short)

getAlgorithm

Added in API level 1

fun getAlgorithm(): String!

Returns the algorithm name of this KeyAgreement object.

This is the same name that was specified in one of the getInstance calls that created this KeyAgreement object.

Return
String!	the algorithm name of this KeyAgreement object.

getInstance

Added in API level 1

static fun getInstance(algorithm: String!): KeyAgreement!

Returns a KeyAgreement object that implements the specified key agreement algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm	String!: the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

Return
KeyAgreement!	the new KeyAgreement object

Exceptions
java.lang.NullPointerException	if the specified algorithm is null.
java.security.NoSuchAlgorithmException	if no Provider supports a KeyAgreementSpi implementation for the specified algorithm.

See Also

• java.security.Provider

getInstance

Added in API level 1

static fun getInstance(
    algorithm: String!, 
    provider: String!
): KeyAgreement!

Returns a KeyAgreement object that implements the specified key agreement algorithm.

A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm	String!: the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider	String!: the name of the provider.

Return
KeyAgreement!	the new KeyAgreement object

Exceptions
java.lang.NullPointerException	if the specified algorithm is null.
java.security.NoSuchAlgorithmException	if a KeyAgreementSpi implementation for the specified algorithm is not available from the specified provider.
java.security.NoSuchProviderException	if the specified provider is not registered in the security provider list.
java.lang.IllegalArgumentException	if the provider is null or empty.

See Also

• java.security.Provider

getInstance

Added in API level 1

static fun getInstance(
    algorithm: String!, 
    provider: Provider!
): KeyAgreement!

Returns a KeyAgreement object that implements the specified key agreement algorithm.

A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

Parameters
algorithm	String!: the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider	Provider!: the provider.

Return
KeyAgreement!	the new KeyAgreement object

Exceptions
java.lang.NullPointerException	if the specified algorithm is null.
java.security.NoSuchAlgorithmException	if a KeyAgreementSpi implementation for the specified algorithm is not available from the specified Provider object.
java.lang.IllegalArgumentException	if the provider is null.

See Also

• java.security.Provider

getProvider

Added in API level 1

fun getProvider(): Provider!

Returns the provider of this KeyAgreement object.

Return
Provider!	the provider of this KeyAgreement object

init

Added in API level 1

fun init(key: Key!): Unit

Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement.

If this key agreement requires any random bytes, it will get them using the java.security.SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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.

Exceptions
java.security.InvalidKeyException	if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.

init

Added in API level 1

fun init(
    key: Key!, 
    random: SecureRandom!
): Unit

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

Exceptions
java.security.InvalidKeyException	if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.

init

Added in API level 1

fun init(
    key: Key!, 
    params: AlgorithmParameterSpec!
): Unit

Initializes this key agreement with the given key and set of algorithm parameters.

If this key agreement requires any random bytes, it will get them using the java.security.SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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

Exceptions
java.security.InvalidKeyException	if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
java.security.InvalidAlgorithmParameterException	if the given parameters are inappropriate for this key agreement.

init

Added in API level 1

fun init(
    key: Key!, 
    params: AlgorithmParameterSpec!, 
    random: SecureRandom!
): Unit

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

Exceptions
java.security.InvalidKeyException	if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
java.security.InvalidAlgorithmParameterException	if the given parameters are inappropriate for this key agreement.