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CipherSpi

public abstract class CipherSpi
extends Object

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 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:

  • "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("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":

  1. Check if the provider has registered a subclass of 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":

  1. Check if the provider has registered a subclass of 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.

  2. Check if the provider has registered a subclass of 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.

  3. Check if the provider has registered a subclass of 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.

  4. Check if the provider has registered a subclass of 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.

See also:

Summary

Public constructors

CipherSpi()

Protected methods

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.

int engineDoFinal(ByteBuffer input, ByteBuffer output)

Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.

abstract byte[] engineDoFinal(byte[] input, int inputOffset, int inputLen)

Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.

abstract int engineGetBlockSize()

Returns the block size (in bytes).

abstract byte[] engineGetIV()

Returns the initialization vector (IV) in a new buffer.

int engineGetKeySize(Key key)

Returns the key size of the given key object in bits.

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).

abstract AlgorithmParameters engineGetParameters()

Returns the parameters used with this cipher.

abstract void engineInit(int opmode, Key key, SecureRandom random)

Initializes this cipher with a key and a source of randomness.

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.

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.

abstract void engineSetMode(String mode)

Sets the mode of this cipher.

abstract void engineSetPadding(String padding)

Sets the padding mechanism of this cipher.

Key engineUnwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType)

Unwrap a previously wrapped key.

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.

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.

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.

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.

void engineUpdateAAD(ByteBuffer src)

Continues a multi-part update of the Additional Authentication Data (AAD).

byte[] engineWrap(Key key)

Wrap a key.

Inherited methods

From class java.lang.Object

Public constructors

CipherSpi

Added in API level 1
CipherSpi ()

Protected methods

engineDoFinal

Added in API level 1
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. The data is encrypted or decrypted, depending on how this cipher was initialized.

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.

Parameters
input byte: the input buffer
inputOffset int: the offset in input where the input starts
inputLen int: the input length
output byte: the buffer for the result
outputOffset int: the offset in output where the result is stored
Returns
int 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 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
AEADBadTagException 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

Added in API level 1
int engineDoFinal (ByteBuffer input, 
                ByteBuffer output)

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 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.

Parameters
input ByteBuffer: the input ByteBuffer
output ByteBuffer: the output ByteByffer
Returns
int 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 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
AEADBadTagException if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value
NullPointerException if either parameter is null

engineDoFinal

Added in API level 1
byte[] engineDoFinal (byte[] input, 
                int inputOffset, 
                int inputLen)

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 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.

Parameters
input byte: the input buffer
inputOffset int: the offset in input where the input starts
inputLen int: the input length
Returns
byte[] 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 bytes
AEADBadTagException if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value

engineGetBlockSize

Added in API level 1
int engineGetBlockSize ()

Returns the block size (in bytes).

Returns
int the block size (in bytes), or 0 if the underlying algorithm is not a block cipher

engineGetIV

Added in API level 1
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
byte[] 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.

engineGetKeySize

Added in API level 1
int engineGetKeySize (Key key)

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 UnsupportedOperationException if it is not overridden by the provider.

Parameters
key Key: the key object.
Returns
int the key size of the given key object.
Throws
InvalidKeyException if key is invalid.

engineGetOutputSize

Added in API level 1
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, 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.

Parameters
inputLen int: the input length (in bytes)
Returns
int the required output buffer size (in bytes)

engineGetParameters

Added in API level 1
AlgorithmParameters 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
AlgorithmParameters the parameters used with this cipher, or null if this cipher does not use any parameters.

engineInit

Added in API level 1
void engineInit (int opmode, 
                Key key, 
                SecureRandom random)

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 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.

Parameters
opmode int: the operation mode of this cipher (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key Key: the encryption key
random SecureRandom: 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.

engineInit

Added in API level 1
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.

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.

Parameters
opmode int: the operation mode of this cipher (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key Key: the encryption key
params AlgorithmParameterSpec: the algorithm parameters
random SecureRandom: the source of randomness
Throws
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 requires algorithm parameters and params is null.

engineInit

Added in API level 1
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.

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.

Parameters
opmode int: the operation mode of this cipher (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key Key: the encryption key
params AlgorithmParameters: the algorithm parameters
random SecureRandom: the source of randomness
Throws
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 requires algorithm parameters and params is null.

engineSetMode

Added in API level 1
void engineSetMode (String mode)

Sets the mode of this cipher.

Parameters
mode String: the cipher mode
Throws
NoSuchAlgorithmException if the requested cipher mode does not exist

engineSetPadding

Added in API level 1
void engineSetPadding (String padding)

Sets the padding mechanism of this cipher.

Parameters
padding String: the padding mechanism
Throws
NoSuchPaddingException if the requested padding mechanism does not exist

engineUnwrap

Added in API level 1
Key engineUnwrap (byte[] wrappedKey, 
                String wrappedKeyAlgorithm, 
                int wrappedKeyType)

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 byte: the key to be unwrapped.
wrappedKeyAlgorithm String: the algorithm associated with the wrapped key.
wrappedKeyType int: the type of the wrapped key. This is one of SECRET_KEY, PRIVATE_KEY, or PUBLIC_KEY.
Returns
Key the unwrapped key.
Throws
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.

engineUpdate

Added in API level 1
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 inclusive, are processed, and the result is stored in a new buffer.

Parameters
input byte: the input buffer
inputOffset int: the offset in input where the input starts
inputLen int: the input length
Returns
byte[] 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

Added in API level 1
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.

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.

Parameters
input byte: the input buffer
inputOffset int: the offset in input where the input starts
inputLen int: the input length
output byte: the buffer for the result
outputOffset int: the offset in output where the result is stored
Returns
int the number of bytes stored in output
Throws
ShortBufferException if the given output buffer is too small to hold the result

engineUpdate

Added in API level 1
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.

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.

Parameters
input ByteBuffer: the input ByteBuffer
output ByteBuffer: the output ByteByffer
Returns
int the number of bytes stored in output
Throws
ShortBufferException if there is insufficient space in the output buffer
NullPointerException if either parameter is null

engineUpdateAAD

Added in API level 19
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 update and doFinal methods).

Parameters
src byte: the buffer containing the AAD
offset int: the offset in src where the AAD input starts
len int: 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 the update methods has already been called for the active encryption/decryption operation
UnsupportedOperationException if this method has not been overridden by an implementation

engineUpdateAAD

Added in API level 19
void engineUpdateAAD (ByteBuffer src)

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 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.

Parameters
src ByteBuffer: 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 the update methods has already been called for the active encryption/decryption operation
UnsupportedOperationException if this method has not been overridden by an implementation

engineWrap

Added in API level 1
byte[] engineWrap (Key key)

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 Key: the key to be wrapped.
Returns
byte[] 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).
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