javax.crypto.CipherSpi
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java.lang.Object
public abstract class CipherSpi
This class defines the Service Provider Interface (SPI)
for the 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., DES), 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("DES/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 DES/ECB/PKCS5Padding,
one that implements
DES/CBC/PKCS5Padding, one that implements
DES/CFB/PKCS5Padding, and yet another one that implements
DES/OFB/PKCS5Padding. That provider would have the following
Cipher properties in its master class:
Cipher.DES/ECB/PKCS5Padding
Cipher.DES/CBC/PKCS5Padding
Cipher.DES/CFB/PKCS5Padding
Cipher.DES/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 DES class that subclasses from
CipherSpi.
That provider would have the following
Cipher properties in its master class:
Cipher.DES
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 Summary | |
|---|---|
CipherSpi()
Creates a new CipherSpi object. |
|
| Method Summary | |
|---|---|
private int |
bufferCrypt(ByteBuffer input,
ByteBuffer output,
boolean isUpdate)
Implementation for encryption using ByteBuffers. |
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 byte[] |
engineWrap(Key key)
Wrap a key. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
|---|
public CipherSpi()
| Method Detail |
|---|
protected abstract void engineSetMode(String mode)
throws NoSuchAlgorithmException
mode - The cipher mode.
NoSuchAlgorithmException - if the requested cipher mode
does not exist.
protected abstract void engineSetPadding(String padding)
throws NoSuchPaddingException
padding - the padding mechanism.
NoSuchPaddingException - if the requested padding mechanism
does not exist.protected 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, and padding.
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 (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 either
ENCRYPT_MODE or DECRYPT_MODE).key - The encryption key.random - The source of randomness.
InvalidKeyException - if the given key is inappropriate for
initializing this cipher
InvalidAlgorithmParameterException - if the given algorithm
parameters are inappropriate for this cipher,
or if this cipher is being initialized for decryption and requires
algorithm parameters and params is null.
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 (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 either
ENCRYPT_MODE or DECRYPT_MODE).key - The encryption key.params - The algorithm parameters.random - The source of randomness.
InvalidKeyException - if the given key is inappropriate for
initializing this cipher
InvalidAlgorithmParameterException - if the given algorithm
parameters are inappropriate for this cipher,
InvalidAlgorithmParameterException - if the given algorithm
parameters are inappropriate for this cipher,
or if this cipher is being initialized for decryption and requires
algorithm parameters and params is null.
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 (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 key.params - the algorithm parameters.random - the source of randomness.
InvalidKeyException - if the given key is inappropriate for
initializing this cipher.
InvalidAlgorithmParameterException - if the given algorithm
parameters are inappropriate for this cipher, or if this cipher
is being initialized for decryption and requires algorithm
parameters and params is null.
protected abstract byte[] engineUpdate(byte[] input,
int inputOffset,
int inputLen)
inputLen bytes in the input buffer, starting
at inputOffset inclusive, are processed, and the
result is stored in a new buffer.
input - the input buffer.inputOffset - the offset in input where the input
starts.inputLen - the input length.
protected abstract int engineUpdate(byte[] input,
int inputOffset,
int inputLen,
byte[] output,
int outputOffset)
throws ShortBufferException
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 buffer.inputOffset - the offset in input where the input
starts.inputLen - the input length.output - the buffer for the result.outputOffset - the offset in output where the
result is stored.
output.
ShortBufferException - if the given output buffer is too
small to hold the result
protected 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 ByteByffer
output
ShortBufferException - if there is insufficient space in the
output buffer
BadPaddingException - DOCUMENT ME!
NullPointerException - if either parameter is null
protected abstract byte[] engineDoFinal(byte[] input,
int inputOffset,
int inputLen)
throws IllegalBlockSizeException,
BadPaddingException
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. 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 buffer.inputOffset - the offset in input where the input
starts.inputLen - the input length.
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.
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 bytes.
protected abstract int engineDoFinal(byte[] input,
int inputOffset,
int inputLen,
byte[] output,
int outputOffset)
throws ShortBufferException,
IllegalBlockSizeException,
BadPaddingException
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. The result is stored in a new buffer.
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 buffer.inputOffset - the offset in input where the input
starts.inputLen - the input length.output - the buffer for the result.outputOffset - the offset in output where the
result is stored.
output
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.
ShortBufferException - if the given output buffer is too
small to hold the result.
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 bytes.
protected int engineDoFinal(ByteBuffer input,
ByteBuffer output)
throws ShortBufferException,
IllegalBlockSizeException,
BadPaddingException
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.
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 ByteByffer
output
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 buffer
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 bytes
NullPointerException - if either parameter is null
protected byte[] engineWrap(Key key)
throws IllegalBlockSizeException,
InvalidKeyException
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 - DOCUMENT ME!
protected Key engineUnwrap(byte[] wrappedKey,
String wrappedKeyAlgorithm,
int wrappedKeyType)
throws InvalidKeyException,
NoSuchAlgorithmException
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.
UnsupportedOperationException - DOCUMENT ME!
InvalidKeyException - if wrappedKey does not represent a
wrapped key of type wrappedKeyType for the
wrappedKeyAlgorithm.
protected int engineGetKeySize(Key key)
throws InvalidKeyException
UnsupportedOperationException if it is not overridden
by the provider.
key - the key object.
InvalidKeyException - if key is invalid.
UnsupportedOperationException - DOCUMENT ME!
private int bufferCrypt(ByteBuffer input,
ByteBuffer output,
boolean isUpdate)
throws ShortBufferException,
IllegalBlockSizeException,
BadPaddingException
ShortBufferException
IllegalBlockSizeException
BadPaddingException
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