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:
- "algorithm/mode/padding" or
- "algorithm"
(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 paddingCipher.algName -
// provider's subclass of "CipherSpi" implements "algName" in the // specified "mode", with pluggable paddingCipher.algName/mode -
// provider's subclass of "CipherSpi" implements "algName" with the // specified "padding", with pluggable modeCipher.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":
-
Check if the provider has registered a subclass of
CipherSpifor 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
NoSuchAlgorithmExceptionexception.
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":
-
Check if the provider has registered a subclass of
CipherSpifor the specified "algorithm/mode/padding" transformation.If the answer is YES, instantiate it.
If the answer is NO, go to the next step.
-
Check if the provider has registered a subclass of
CipherSpifor 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.
-
Check if the provider has registered a subclass of
CipherSpifor 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.
-
Check if the provider has registered a subclass of
CipherSpifor the sub-transformation "algorithm".If the answer is YES, instantiate it, and call
engineSetMode(mode)andengineSetPadding(padding)on the new instance.If the answer is NO, throw a
NoSuchAlgorithmExceptionexception.
- Since:
- 1.4
- See Also:
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprotected 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 intengineDoFinal(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 intengineDoFinal(ByteBuffer input, ByteBuffer output) Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.protected abstract intReturns the block size (in bytes).protected abstract byte[]Returns the initialization vector (IV) in a new buffer.protected intengineGetKeySize(Key key) Returns the key size of the given key object in bits.protected abstract intengineGetOutputSize(int inputLen) Returns the length in bytes that an output buffer would need to be in order to hold the result of the nextupdateordoFinaloperation, given the input lengthinputLen(in bytes).protected abstract AlgorithmParametersReturns the parameters used with this cipher.protected abstract voidengineInit(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 voidengineInit(int opmode, Key key, SecureRandom random) Initializes this cipher with a key and a source of randomness.protected abstract voidengineInit(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 voidengineSetMode(String mode) Sets the mode of this cipher.protected abstract voidengineSetPadding(String padding) Sets the padding mechanism of this cipher.protected KeyengineUnwrap(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 intengineUpdate(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 intengineUpdate(ByteBuffer input, ByteBuffer output) Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.protected voidengineUpdateAAD(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 voidContinues a multi-part update of the Additional Authentication Data (AAD).protected byte[]engineWrap(Key key) Wrap a key.
-
Constructor Details
-
CipherSpi
public CipherSpi()Constructor for subclasses to call.
-
-
Method Details
-
engineSetMode
Sets the mode of this cipher.- Parameters:
mode- the cipher mode- Throws:
NoSuchAlgorithmException- if the requested cipher mode does not exist
-
engineSetPadding
Sets the padding mechanism of this cipher.- Parameters:
padding- the padding mechanism- Throws:
NoSuchPaddingException- if the requested padding mechanism does not exist
-
engineGetBlockSize
protected abstract int engineGetBlockSize()Returns the block size (in bytes).- Returns:
- the block size (in bytes), or 0 if the underlying algorithm is not a block cipher
-
engineGetOutputSize
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 nextupdateordoFinaloperation, given the input lengthinputLen(in bytes).This call takes into account any unprocessed (buffered) data from a previous
updatecall, padding, and AEAD tagging.The actual output length of the next
updateordoFinalcall may be smaller than the length returned by this method.- Parameters:
inputLen- the input length (in bytes)- Returns:
- the required output buffer size (in bytes)
-
engineGetIV
protected abstract byte[] engineGetIV()Returns the initialization vector (IV) in a new buffer.This is useful in the context of password-based encryption or decryption, where the IV is derived from a user-provided passphrase.
- Returns:
- the initialization vector in a new buffer, or null if the underlying algorithm does not use an IV, or if the IV has not yet been set.
-
engineGetParameters
Returns the parameters used with this cipher.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.
- Returns:
- the parameters used with this cipher, or null if this cipher does not use any parameters.
-
engineInit
protected abstract void engineInit(int opmode, Key key, SecureRandom random) throws InvalidKeyException Initializes this cipher with a key and a source of randomness.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 anInvalidKeyExceptionif it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved usingengineGetParametersorengineGetIV(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.
- Parameters:
opmode- the operation mode of this cipher (this is one of the following:ENCRYPT_MODE,DECRYPT_MODE,WRAP_MODEorUNWRAP_MODE)key- the encryption keyrandom- the source of randomness- Throws:
InvalidKeyException- if the given key is inappropriate for initializing this cipher, or requires algorithm parameters that cannot be determined from the given key.UnsupportedOperationException- ifopmodeisWRAP_MODEorUNWRAP_MODEis not implemented by the cipher.
-
engineInit
protected abstract void engineInit(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.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
paramsis 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 anInvalidAlgorithmParameterExceptionif it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved usingengineGetParametersorengineGetIV(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.
- Parameters:
opmode- the operation mode of this cipher (this is one of the following:ENCRYPT_MODE,DECRYPT_MODE,WRAP_MODEorUNWRAP_MODE)key- the encryption keyparams- the algorithm parametersrandom- the source of randomness- Throws:
InvalidKeyException- 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 andparamsis null.UnsupportedOperationException- ifopmodeisWRAP_MODEorUNWRAP_MODEis not implemented by the cipher.
-
engineInit
protected abstract void engineInit(int opmode, Key key, AlgorithmParameters params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.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
paramsis 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 anInvalidAlgorithmParameterExceptionif it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved usingengineGetParametersorengineGetIV(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.
- Parameters:
opmode- the operation mode of this cipher (this is one of the following:ENCRYPT_MODE,DECRYPT_MODE,WRAP_MODEorUNWRAP_MODE)key- the encryption keyparams- the algorithm parametersrandom- the source of randomness- Throws:
InvalidKeyException- 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 andparamsis null.UnsupportedOperationException- ifopmodeisWRAP_MODEorUNWRAP_MODEis not implemented by the cipher.
-
engineUpdate
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.The first
inputLenbytes in theinputbuffer, starting atinputOffsetinclusive, are processed, and the result is stored in a new buffer.- Parameters:
input- the input bufferinputOffset- the offset ininputwhere the input startsinputLen- the input length- Returns:
- the new buffer with the result, or null if the underlying cipher is a block cipher and the input data is too short to result in a new block.
-
engineUpdate
protected abstract int engineUpdate(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.The first
inputLenbytes in theinputbuffer, starting atinputOffsetinclusive, are processed, and the result is stored in theoutputbuffer, starting atoutputOffsetinclusive.If the
outputbuffer is too small to hold the result, aShortBufferExceptionis thrown.- Parameters:
input- the input bufferinputOffset- the offset ininputwhere the input startsinputLen- the input lengthoutput- the buffer for the resultoutputOffset- the offset inoutputwhere the result is stored- Returns:
- the number of bytes stored in
output - Throws:
ShortBufferException- if the given output buffer is too small to hold the result
-
engineUpdate
Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.All
input.remaining()bytes starting atinput.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, aShortBufferExceptionis thrown.Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.
- Parameters:
input- the input ByteBufferoutput- the output ByteByffer- Returns:
- the number of bytes stored in
output - Throws:
ShortBufferException- if there is insufficient space in the output bufferNullPointerException- if either parameter isnull- Since:
- 1.5
-
engineDoFinal
protected abstract byte[] engineDoFinal(byte[] input, int inputOffset, int inputLen) throws IllegalBlockSizeException, BadPaddingException Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.The first
inputLenbytes in theinputbuffer, starting atinputOffsetinclusive, and any input bytes that may have been buffered during a previousupdateoperation, 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 toengineInit) more data.Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.
- Parameters:
input- the input bufferinputOffset- the offset ininputwhere the input startsinputLen- the input length- Returns:
- the new buffer with the result
- Throws:
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.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 value
-
engineDoFinal
protected abstract int engineDoFinal(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.The first
inputLenbytes in theinputbuffer, starting atinputOffsetinclusive, and any input bytes that may have been buffered during a previousupdateoperation, 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 theoutputbuffer, starting atoutputOffsetinclusive.If the
outputbuffer is too small to hold the result, aShortBufferExceptionis 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 toengineInit) more data.Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.
- Parameters:
input- the input bufferinputOffset- the offset ininputwhere the input startsinputLen- the input lengthoutput- the buffer for the resultoutputOffset- the offset inoutputwhere the result is stored- Returns:
- the number of bytes stored in
output - Throws:
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 value
-
engineDoFinal
protected int engineDoFinal(ByteBuffer input, ByteBuffer output) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.All
input.remaining()bytes starting atinput.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, aShortBufferExceptionis 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 toengineInit) 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.
- Parameters:
input- the input ByteBufferoutput- the output ByteByffer- Returns:
- the number of bytes stored in
output - Throws:
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 isnull- Since:
- 1.5
-
engineWrap
Wrap a key.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.
- Parameters:
key- the key to be wrapped.- Returns:
- the wrapped key.
- Throws:
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.
-
engineUnwrap
protected Key engineUnwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType) throws InvalidKeyException, NoSuchAlgorithmException Unwrap a previously wrapped key.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.
- Parameters:
wrappedKey- the key to be unwrapped.wrappedKeyAlgorithm- the algorithm associated with the wrapped key.wrappedKeyType- the type of the wrapped key. This is one ofSECRET_KEY,PRIVATE_KEY, orPUBLIC_KEY.- Returns:
- the unwrapped key.
- Throws:
NoSuchAlgorithmException- if no installed providers can create keys of typewrappedKeyTypefor thewrappedKeyAlgorithm.InvalidKeyException- ifwrappedKeydoes not represent a wrapped key of typewrappedKeyTypefor thewrappedKeyAlgorithm.UnsupportedOperationException- if this method is not supported.
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engineGetKeySize
Returns the key size of the given key object in bits.This concrete method has been added to this previously-defined abstract class. It throws an
UnsupportedOperationExceptionif it is not overridden by the provider.- Parameters:
key- the key object.- Returns:
- the key size of the given key object.
- Throws:
InvalidKeyException- ifkeyis invalid.
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engineUpdateAAD
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.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
updateanddoFinalmethods).- Parameters:
src- the buffer containing the AADoffset- the offset insrcwhere the AAD input startslen- the number of AAD bytes- Throws:
IllegalStateException- 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 theupdatemethods has already been called for the active encryption/decryption operationUnsupportedOperationException- if this method has not been overridden by an implementation- Since:
- 1.7
-
engineUpdateAAD
Continues a multi-part update of the Additional Authentication Data (AAD).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
updateanddoFinalmethods).All
src.remaining()bytes starting atsrc.position()are processed. Upon return, the input buffer's position will be equal to its limit; its limit will not have changed.- Parameters:
src- the buffer containing the AAD- Throws:
IllegalStateException- 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 theupdatemethods has already been called for the active encryption/decryption operationUnsupportedOperationException- if this method has not been overridden by an implementation- Since:
- 1.7
-