- Enclosing class:
KEM
KEM.newDecapsulator(java.security.PrivateKey)
on the KEM
receiver side.
This class represents the key decapsulation function of a KEM.
An invocation of the decapsulate
method recovers the
secret key from the key encapsulation message.
- Since:
- 21
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Method Summary
Modifier and TypeMethodDescriptiondecapsulate
(byte[] encapsulation) The key decapsulation function.decapsulate
(byte[] encapsulation, int from, int to, String algorithm) The key decapsulation function.int
Returns the size of the key encapsulation message.Returns the name of the provider.int
Returns the size of the shared secret.
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Method Details
-
providerName
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decapsulate
The key decapsulation function.This method is equivalent to
decapsulate(encapsulation, 0, secretSize(), "Generic")
. This combination of arguments must be supported by every implementation.The generated secret key is usually passed to a key derivation function (KDF) as the input keying material.
- Parameters:
encapsulation
- the key encapsulation message from the sender. The size must be equal to the value returned byencapsulationSize()
, or aDecapsulateException
will be thrown.- Returns:
- the shared secret as a
SecretKey
with an algorithm name of "Generic" - Throws:
DecapsulateException
- if an error occurs during the decapsulation processNullPointerException
- ifencapsulation
isnull
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decapsulate
public SecretKey decapsulate(byte[] encapsulation, int from, int to, String algorithm) throws DecapsulateException The key decapsulation function.An invocation of this method recovers the secret key from the key encapsulation message.
An implementation may choose to not support arbitrary combinations of
from
,to
, andalgorithm
.- Parameters:
encapsulation
- the key encapsulation message from the sender. The size must be equal to the value returned byencapsulationSize()
, or aDecapsulateException
will be thrown.from
- the initial index of the shared secret byte array to be returned, inclusiveto
- the final index of the shared secret byte array to be returned, exclusivealgorithm
- the algorithm name for the secret key that is returned- Returns:
- a portion of the shared secret as a
SecretKey
containing the bytes of the secret ranging fromfrom
toto
, exclusive, and an algorithm name as specified. For example,decapsulate(encapsulation, secretSize() - 16, secretSize(), "AES")
uses the last 16 bytes of the shared secret as a 128-bit AES key. - Throws:
DecapsulateException
- if an error occurs during the decapsulation processIndexOutOfBoundsException
- iffrom < 0
,from > to
, orto > secretSize()
NullPointerException
- ifencapsulation
oralgorithm
isnull
UnsupportedOperationException
- if the combination offrom
,to
, andalgorithm
is not supported by the decapsulator
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secretSize
public int secretSize()Returns the size of the shared secret.This method can be called to find out the length of the shared secret before
decapsulate
is called or if the obtainedSecretKey
is not extractable.- Returns:
- the size of the shared secret
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encapsulationSize
public int encapsulationSize()Returns the size of the key encapsulation message.This method can be used to extract the encapsulation message from a longer byte array if no length information is provided by a higher level protocol.
- Returns:
- the size of the key encapsulation message
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