public abstract class CipherSpi extends Object
Cipher
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 cipher algorithm.
In order to create an instance of Cipher
, which
encapsulates an instance of this CipherSpi
class, an
application calls one of the
getInstance
factory methods of the
Cipher
engine class and specifies the requested
transformation.
Optionally, the application may also specify the name of a provider.
A transformation is a string that describes the operation (or set of operations) to be performed on the given input, to produce some output. A transformation always includes the name of a cryptographic algorithm (e.g., AES), and may be followed by a feedback mode and padding scheme.
A transformation is of the form:
(in the latter case, provider-specific default values for the mode and padding scheme are used). For example, the following is a valid transformation:
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
A provider may supply a separate class for each combination
of algorithm/mode/padding, or may decide to provide more generic
classes representing sub-transformations corresponding to
algorithm or algorithm/mode or algorithm//padding
(note the double slashes),
in which case the requested mode and/or padding are set automatically by
the getInstance
methods of Cipher
, which invoke
the engineSetMode
and
engineSetPadding
methods of the provider's subclass of CipherSpi
.
A Cipher
property in a provider master class may have one of
the following formats:
// provider's subclass of "CipherSpi" implements "algName" with
// pluggable mode and padding
Cipher.
algName
// provider's subclass of "CipherSpi" implements "algName" in the
// specified "mode", with pluggable padding
Cipher.
algName/mode
// provider's subclass of "CipherSpi" implements "algName" with the
// specified "padding", with pluggable mode
Cipher.
algName//padding
// provider's subclass of "CipherSpi" implements "algName" with the
// specified "mode" and "padding"
Cipher.
algName/mode/padding
For example, a provider may supply a subclass of CipherSpi
that implements AES/ECB/PKCS5Padding, one that implements
AES/CBC/PKCS5Padding, one that implements
AES/CFB/PKCS5Padding, and yet another one that implements
AES/OFB/PKCS5Padding. That provider would have the following
Cipher
properties in its master class:
Cipher.
AES/ECB/PKCS5Padding
Cipher.
AES/CBC/PKCS5Padding
Cipher.
AES/CFB/PKCS5Padding
Cipher.
AES/OFB/PKCS5Padding
Another provider may implement a class for each of the above modes
(i.e., one class for ECB, one for CBC, one for CFB,
and one for OFB), one class for PKCS5Padding,
and a generic AES class that subclasses from CipherSpi
.
That provider would have the following
Cipher
properties in its master class:
Cipher.
AES
The getInstance
factory method of the Cipher
engine class follows these rules in order to instantiate a provider's
implementation of CipherSpi
for a
transformation of the form "algorithm":
CipherSpi
for the specified "algorithm".
If the answer is YES, instantiate this class, for whose mode and padding scheme default values (as supplied by the provider) are used.
If the answer is NO, throw a NoSuchAlgorithmException
exception.
The getInstance
factory method of the Cipher
engine class follows these rules in order to instantiate a provider's
implementation of CipherSpi
for a
transformation of the form "algorithm/mode/padding":
CipherSpi
for the specified "algorithm/mode/padding" transformation.
If the answer is YES, instantiate it.
If the answer is NO, go to the next step.
CipherSpi
for the sub-transformation "algorithm/mode".
If the answer is YES, instantiate it, and call
engineSetPadding(padding)
on the new instance.
If the answer is NO, go to the next step.
CipherSpi
for the sub-transformation "algorithm//padding" (note the double
slashes).
If the answer is YES, instantiate it, and call
engineSetMode(mode)
on the new instance.
If the answer is NO, go to the next step.
CipherSpi
for the sub-transformation "algorithm".
If the answer is YES, instantiate it, and call
engineSetMode(mode)
and
engineSetPadding(padding)
on the new instance.
If the answer is NO, throw a NoSuchAlgorithmException
exception.
KeyGenerator
,
SecretKey
Constructor and Description |
---|
CipherSpi() |
Modifier and Type | Method and Description |
---|---|
protected abstract byte[] |
engineDoFinal(byte[] input,
int inputOffset,
int inputLen)
Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
|
protected abstract int |
engineDoFinal(byte[] input,
int inputOffset,
int inputLen,
byte[] output,
int outputOffset)
Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
|
protected int |
engineDoFinal(ByteBuffer input,
ByteBuffer output)
Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
|
protected abstract int |
engineGetBlockSize()
Returns the block size (in bytes).
|
protected abstract byte[] |
engineGetIV()
Returns the initialization vector (IV) in a new buffer.
|
protected int |
engineGetKeySize(Key key)
Returns the key size of the given key object in bits.
|
protected abstract int |
engineGetOutputSize(int inputLen)
Returns the length in bytes that an output buffer would
need to be in order to hold the result of the next
update
or doFinal operation, given the input length
inputLen (in bytes). |
protected abstract AlgorithmParameters |
engineGetParameters()
Returns the parameters used with this cipher.
|
protected abstract void |
engineInit(int opmode,
Key key,
AlgorithmParameterSpec params,
SecureRandom random)
Initializes this cipher with a key, a set of
algorithm parameters, and a source of randomness.
|
protected abstract void |
engineInit(int opmode,
Key key,
AlgorithmParameters params,
SecureRandom random)
Initializes this cipher with a key, a set of
algorithm parameters, and a source of randomness.
|
protected abstract void |
engineInit(int opmode,
Key key,
SecureRandom random)
Initializes this cipher with a key and a source
of randomness.
|
protected abstract void |
engineSetMode(String mode)
Sets the mode of this cipher.
|
protected abstract void |
engineSetPadding(String padding)
Sets the padding mechanism of this cipher.
|
protected Key |
engineUnwrap(byte[] wrappedKey,
String wrappedKeyAlgorithm,
int wrappedKeyType)
Unwrap a previously wrapped key.
|
protected abstract byte[] |
engineUpdate(byte[] input,
int inputOffset,
int inputLen)
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
|
protected abstract int |
engineUpdate(byte[] input,
int inputOffset,
int inputLen,
byte[] output,
int outputOffset)
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
|
protected int |
engineUpdate(ByteBuffer input,
ByteBuffer output)
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
|
protected void |
engineUpdateAAD(byte[] src,
int offset,
int len)
Continues a multi-part update of the Additional Authentication
Data (AAD), using a subset of the provided buffer.
|
protected void |
engineUpdateAAD(ByteBuffer src)
Continues a multi-part update of the Additional Authentication
Data (AAD).
|
protected byte[] |
engineWrap(Key key)
Wrap a key.
|
protected abstract void engineSetMode(String mode) throws NoSuchAlgorithmException
mode
- the cipher modeNoSuchAlgorithmException
- if the requested cipher mode does
not existprotected abstract void engineSetPadding(String padding) throws NoSuchPaddingException
padding
- the padding mechanismNoSuchPaddingException
- if the requested padding mechanism
does not existprotected abstract int engineGetBlockSize()
protected abstract int engineGetOutputSize(int inputLen)
update
or doFinal
operation, given the input length
inputLen
(in bytes).
This call takes into account any unprocessed (buffered) data from a
previous update
call, padding, and AEAD tagging.
The actual output length of the next update
or
doFinal
call may be smaller than the length returned by
this method.
inputLen
- the input length (in bytes)protected abstract byte[] engineGetIV()
This is useful in the context of password-based encryption or decryption, where the IV is derived from a user-provided passphrase.
protected abstract AlgorithmParameters engineGetParameters()
The returned parameters may be the same that were used to initialize this cipher, or may contain a combination of default and random parameter values used by the underlying cipher implementation if this cipher requires algorithm parameters but was not initialized with any.
protected abstract void engineInit(int opmode, Key key, SecureRandom random) throws InvalidKeyException
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of opmode
.
If this cipher requires any algorithm parameters that cannot be
derived from the given key
, the underlying cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidKeyException
if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
engineGetParameters
or
engineGetIV
(if the parameter is an IV).
If this cipher requires algorithm parameters that cannot be derived from the input parameters, and there are no reasonable provider-specific default values, initialization will necessarily fail.
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random
.
Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher and initializing it.
opmode
- the operation mode of this cipher (this is one of
the following:
ENCRYPT_MODE
, DECRYPT_MODE
,
WRAP_MODE
or UNWRAP_MODE
)key
- the encryption keyrandom
- the source of randomnessInvalidKeyException
- if the given key is inappropriate for
initializing this cipher, or requires
algorithm parameters that cannot be
determined from the given key.UnsupportedOperationException
- if opmode
is
WRAP_MODE
or UNWRAP_MODE
is not implemented
by the cipher.protected abstract void engineInit(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of opmode
.
If this cipher requires any algorithm parameters and
params
is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException
if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
engineGetParameters
or
engineGetIV
(if the parameter is an IV).
If this cipher requires algorithm parameters that cannot be derived from the input parameters, and there are no reasonable provider-specific default values, initialization will necessarily fail.
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random
.
Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher and initializing it.
opmode
- the operation mode of this cipher (this is one of
the following:
ENCRYPT_MODE
, DECRYPT_MODE
,
WRAP_MODE
or UNWRAP_MODE
)key
- the encryption keyparams
- the algorithm parametersrandom
- the source of randomnessInvalidKeyException
- if the given key is inappropriate for
initializing this cipherInvalidAlgorithmParameterException
- if the given algorithm
parameters are inappropriate for this cipher,
or if this cipher requires
algorithm parameters and params
is null.UnsupportedOperationException
- if opmode
is
WRAP_MODE
or UNWRAP_MODE
is not implemented
by the cipher.protected abstract void engineInit(int opmode, Key key, AlgorithmParameters params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of opmode
.
If this cipher requires any algorithm parameters and
params
is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException
if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
engineGetParameters
or
engineGetIV
(if the parameter is an IV).
If this cipher requires algorithm parameters that cannot be derived from the input parameters, and there are no reasonable provider-specific default values, initialization will necessarily fail.
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random
.
Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher and initializing it.
opmode
- the operation mode of this cipher (this is one of
the following:
ENCRYPT_MODE
, DECRYPT_MODE
,
WRAP_MODE
or UNWRAP_MODE
)key
- the encryption keyparams
- the algorithm parametersrandom
- the source of randomnessInvalidKeyException
- if the given key is inappropriate for
initializing this cipherInvalidAlgorithmParameterException
- if the given algorithm
parameters are inappropriate for this cipher,
or if this cipher requires
algorithm parameters and params
is null.UnsupportedOperationException
- if opmode
is
WRAP_MODE
or UNWRAP_MODE
is not implemented
by the cipher.protected abstract byte[] engineUpdate(byte[] input, int inputOffset, int inputLen)
The first inputLen
bytes in the input
buffer, starting at inputOffset
inclusive, are processed,
and the result is stored in a new buffer.
input
- the input bufferinputOffset
- the offset in input
where the input
startsinputLen
- the input lengthprotected abstract int engineUpdate(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException
The first inputLen
bytes in the input
buffer, starting at inputOffset
inclusive, are processed,
and the result is stored in the output
buffer, starting at
outputOffset
inclusive.
If the output
buffer is too small to hold the result,
a ShortBufferException
is thrown.
input
- the input bufferinputOffset
- the offset in input
where the input
startsinputLen
- the input lengthoutput
- the buffer for the resultoutputOffset
- the offset in output
where the result
is storedoutput
ShortBufferException
- if the given output buffer is too small
to hold the resultprotected int engineUpdate(ByteBuffer input, ByteBuffer output) throws ShortBufferException
All input.remaining()
bytes starting at
input.position()
are processed. The result is stored
in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.
If output.remaining()
bytes are insufficient to
hold the result, a ShortBufferException
is thrown.
Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.
input
- the input ByteBufferoutput
- the output ByteByfferoutput
ShortBufferException
- if there is insufficient space in the
output bufferNullPointerException
- if either parameter is null
protected abstract byte[] engineDoFinal(byte[] input, int inputOffset, int inputLen) throws IllegalBlockSizeException, BadPaddingException
The first inputLen
bytes in the input
buffer, starting at inputOffset
inclusive, and any input
bytes that may have been buffered during a previous update
operation, are processed, with padding (if requested) being applied.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in a new buffer.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
engineInit
.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
engineInit
) more data.
Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.
input
- the input bufferinputOffset
- the offset in input
where the input
startsinputLen
- the input lengthIllegalBlockSizeException
- if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.BadPaddingException
- if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytesAEADBadTagException
- if this cipher is decrypting in an
AEAD mode (such as GCM/CCM), and the received authentication tag
does not match the calculated valueprotected abstract int engineDoFinal(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException
The first inputLen
bytes in the input
buffer, starting at inputOffset
inclusive, and any input
bytes that may have been buffered during a previous update
operation, are processed, with padding (if requested) being applied.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in the output
buffer, starting at
outputOffset
inclusive.
If the output
buffer is too small to hold the result,
a ShortBufferException
is thrown.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
engineInit
.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
engineInit
) more data.
Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.
input
- the input bufferinputOffset
- the offset in input
where the input
startsinputLen
- the input lengthoutput
- the buffer for the resultoutputOffset
- the offset in output
where the result
is storedoutput
IllegalBlockSizeException
- if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.ShortBufferException
- if the given output buffer is too small
to hold the resultBadPaddingException
- if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytesAEADBadTagException
- if this cipher is decrypting in an
AEAD mode (such as GCM/CCM), and the received authentication tag
does not match the calculated valueprotected int engineDoFinal(ByteBuffer input, ByteBuffer output) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException
All input.remaining()
bytes starting at
input.position()
are processed.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.
If output.remaining()
bytes are insufficient to
hold the result, a ShortBufferException
is thrown.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
engineInit
.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
engineInit
) more data.
Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.
Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.
input
- the input ByteBufferoutput
- the output ByteByfferoutput
IllegalBlockSizeException
- if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.ShortBufferException
- if there is insufficient space in the
output bufferBadPaddingException
- if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytesAEADBadTagException
- if this cipher is decrypting in an
AEAD mode (such as GCM/CCM), and the received authentication tag
does not match the calculated valueNullPointerException
- if either parameter is null
protected byte[] engineWrap(Key key) throws IllegalBlockSizeException, InvalidKeyException
This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.) It may be overridden by a provider to wrap a key. Such an override is expected to throw an IllegalBlockSizeException or InvalidKeyException (under the specified circumstances), if the given key cannot be wrapped. If this method is not overridden, it always throws an UnsupportedOperationException.
key
- the key to be wrapped.IllegalBlockSizeException
- if this cipher is a block cipher,
no padding has been requested, and the length of the encoding of the
key to be wrapped is not a multiple of the block size.InvalidKeyException
- if it is impossible or unsafe to
wrap the key with this cipher (e.g., a hardware protected key is
being passed to a software-only cipher).UnsupportedOperationException
- if this method is not supported.protected Key engineUnwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType) throws InvalidKeyException, NoSuchAlgorithmException
This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.) It may be overridden by a provider to unwrap a previously wrapped key. Such an override is expected to throw an InvalidKeyException if the given wrapped key cannot be unwrapped. If this method is not overridden, it always throws an UnsupportedOperationException.
wrappedKey
- the key to be unwrapped.wrappedKeyAlgorithm
- the algorithm associated with the wrapped
key.wrappedKeyType
- the type of the wrapped key. This is one of
SECRET_KEY
, PRIVATE_KEY
, or
PUBLIC_KEY
.NoSuchAlgorithmException
- if no installed providers
can create keys of type wrappedKeyType
for the
wrappedKeyAlgorithm
.InvalidKeyException
- if wrappedKey
does not
represent a wrapped key of type wrappedKeyType
for
the wrappedKeyAlgorithm
.UnsupportedOperationException
- if this method is not supported.protected int engineGetKeySize(Key key) throws InvalidKeyException
This concrete method has been added to this previously-defined
abstract class. It throws an UnsupportedOperationException
if it is not overridden by the provider.
key
- the key object.InvalidKeyException
- if key
is invalid.protected void engineUpdateAAD(byte[] src, int offset, int len)
Calls to this method provide AAD to the cipher when operating in
modes such as AEAD (GCM/CCM). If this cipher is operating in
either GCM or CCM mode, all AAD must be supplied before beginning
operations on the ciphertext (via the update
and doFinal
methods).
src
- the buffer containing the AADoffset
- the offset in src
where the AAD input startslen
- the number of AAD bytesIllegalStateException
- if this cipher is in a wrong state
(e.g., has not been initialized), does not accept AAD, or if
operating in either GCM or CCM mode and one of the update
methods has already been called for the active
encryption/decryption operationUnsupportedOperationException
- if this method
has not been overridden by an implementationprotected void engineUpdateAAD(ByteBuffer src)
Calls to this method provide AAD to the cipher when operating in
modes such as AEAD (GCM/CCM). If this cipher is operating in
either GCM or CCM mode, all AAD must be supplied before beginning
operations on the ciphertext (via the update
and doFinal
methods).
All src.remaining()
bytes starting at
src.position()
are processed.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed.
src
- the buffer containing the AADIllegalStateException
- if this cipher is in a wrong state
(e.g., has not been initialized), does not accept AAD, or if
operating in either GCM or CCM mode and one of the update
methods has already been called for the active
encryption/decryption operationUnsupportedOperationException
- if this method
has not been overridden by an implementation Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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