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java.lang.Object | +--javax.crypto.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 the getInstance method of Cipher 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: algorithm or algorithm/mode/padding (in the former case, defaults are used for mode and padding). For example, DES/CBC/PKCS5Padding represents a valid transformation.
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, whose mode and/or padding schemes can be set using engineSetMode and engineSetPadding, respectively.
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.
A different 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.
The algorithm for instantiating a Cipher object (using one of the getInstance methods) when a transformation of the form algorithm is given is as follows:
The algorithm for instantiating a CipherSpi object when a transformation of the form algorithm/mode/padding is given is as follows:
KeyGenerator
,
SecretKey
,
java.security.KeyPairGenerator
,
PublicKey
,
PrivateKey
,
AlgorithmParameters
,
AlgorithmParameterSpec
Field Summary | |
protected int |
state
|
Constructor Summary | |
CipherSpi()
|
Method Summary | |
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 abstract int |
engineGetBlockSize()
Returns the block size (in bytes). |
protected abstract byte[] |
engineGetIV()
Returns the initialization vector (IV) in a new buffer. |
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 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. |
Methods inherited from class java.lang.Object |
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait |
Field Detail |
protected int state
Constructor Detail |
public CipherSpi()
Method Detail |
protected abstract void engineSetMode(String mode) throws NoSuchAlgorithmException
mode
- the cipher modeprotected abstract void engineSetPadding(String padding) throws NoSuchPaddingException
padding
- the padding mechanismprotected abstract int engineGetBlockSize()
Returns the block size (in bytes).
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).
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()
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.
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 encryption or decryption, depending on the value of opmode.
If this cipher requires an initialization vector (IV), it will get it from random. The random IV can be retrieved using getIV. This behaviour should only be used in encryption mode, however. When initializing a cipher that requires an IV for decryption, the IV (same IV that was used for encryption) must be provided explicitly as a parameter, in order to get the correct result. 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 keyrandom
- the source of randomnessprotected 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 encryption or decryption, depending on the value of opmode. If this cipher (including its underlying feedback or padding scheme) requires any random bytes, 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 keyparams
- the algorithm parametersrandom
- the source of randomnessprotected 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 encryption or decryption, depending on the value of opmode.
f 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, and raise an InvalidAlgorithmParameterException if it is being initialized for decryption. The generated parameters can be retrieved using engineGetParameters or engineGetIV (if the parameter is an IV).
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 keyparams
- the algorithm parametersrandom
- the source of randomnessprotected 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 inputLen bytes in the input buffer, starting at inputOffset, 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
Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
The first inputLen bytes in the input buffer, starting at inputOffset, are processed, and the result is stored in the output buffer, starting at outputOffset.
If the output buffer is too small to hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be.
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 storedprotected 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 inputLen bytes in the input buffer, starting at inputOffset, 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.
A call to this method resets this cipher object to the state it was in when previously initialized via a call to init. That is, the object is reset and available to encrypt or decrypt (depending on the operation mode that was specified in the call to init) more data.
input
- the input bufferinputOffset
- the offset in input where the input startsinputLen
- the input lengthprotected 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 inputLen bytes in the input buffer, starting at inputOffset, 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 the output buffer, starting at outputOffset.
If the output buffer is too small to hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be.
A call to this method resets this cipher object to the state it was in when previously initialized via a call to init. That is, the object is reset and available to encrypt or decrypt (depending on the operation mode that was specified in the call to init) more data.
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 isprotected abstract AlgorithmParameters engineGetParameters()
The returned parameters may be the same that were used to initialize this cipher, or may contain the default set of parameters or a set of randomly generated parameters used by the underlying cipher implementation (provided that the underlying cipher implementation uses a default set of parameters or creates new parameters if it needs parameters but was not initialized with any).
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