javax.crypto
Class Cipher

java.lang.Object
  |
  +--javax.crypto.Cipher
Direct Known Subclasses:
NullCipher

public class Cipher
extends Object

This class provides the functionality of a cryptographic cipher for encryption and decryption. It forms the core of the Java Cryptographic Extension (JCE) framework.

In order to create a Cipher object, the application calls the Cipher's getInstance method, and passes the name of the requested transformation to it. Optionally, the name of a provider may be specified.

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.

See Also:
KeyGenerator, SecretKey, java.security.KeyPairGenerator, PublicKey, PrivateKey, AlgorithmParameters, AlgorithmParameterSpec

Field Summary
static int DECRYPT_MODE
           
static int ENCRYPT_MODE
           
 
Constructor Summary
protected Cipher(CipherSpi cipherSpi, Provider provider, String transformation)
          Creates a Cipher object.
 
Method Summary
 byte[] doFinal()
          Finishes a multiple-part encryption or decryption operation, depending on how this cipher was initialized.
 byte[] doFinal(byte[] input)
          Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
 int doFinal(byte[] output, int outputOffset)
          Finishes a multiple-part encryption or decryption operation, depending on how this cipher was initialized.
 byte[] doFinal(byte[] input, int inputOffset, int inputLen)
          Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
 int doFinal(byte[] input, int inputOffset, int inputLen, byte[] output)
          Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
 int doFinal(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.
 String getAlgorithm()
          Returns the algorithm name of this Cipher object.
 int getBlockSize()
          Returns the block size (in bytes).
static Cipher getInstance(String transformation)
          Creates a Cipher object that implements the specified algorithm, as supplied by the default provider.
static Cipher getInstance(String transformation, String provider)
          Creates a Cipher object that implements the specified transformation, as supplied by the specified provider.
 byte[] getIV()
          Returns the initialization vector (IV) in a new buffer.
 int getOutputSize(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).
 AlgorithmParameters getParameters()
          Returns the parameters used with this cipher.
 Provider getProvider()
          Returns the provider of this Cipher object.
 void init(int opmode, Key key)
          Initializes this cipher with a key.
 void init(int opmode, Key key, AlgorithmParameters params)
          Initializes this cipher with a key and a set of algorithm parameters.
 void init(int opmode, Key key, AlgorithmParameterSpec params)
          Initializes this cipher with a key and a set of algorithm parameters.
 void init(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random)
          Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.
 void init(int opmode, Key key, AlgorithmParameters params, SecureRandom random)
          Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.
 void init(int opmode, Key key, SecureRandom random)
          Initializes this cipher with a key and a source of randomness.
 byte[] update(byte[] input)
          Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
 byte[] update(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.
 int update(byte[] input, int inputOffset, int inputLen, byte[] output)
          Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
 int update(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

ENCRYPT_MODE

public static final int ENCRYPT_MODE

DECRYPT_MODE

public static final int DECRYPT_MODE
Constructor Detail

Cipher

protected Cipher(CipherSpi cipherSpi,
                 Provider provider,
                 String transformation)
Creates a Cipher object.
Parameters:
cipherSpi - the delegate
provider - the provider
transformation - the transformation
Method Detail

getInstance

public static final Cipher getInstance(String transformation)
                                throws NoSuchAlgorithmException,
                                       NoSuchPaddingException
Creates a Cipher object that implements the specified algorithm, as supplied by the default provider.
Parameters:
transformation - the string representation of the requested transformation, e.g., DES/CBC/PKCS5Padding
Returns:
a cipher that implements the requested transformation
Throws:
NoSuchAlgorithmException - if the transformation is not available in the caller's environment.
NoSuchPaddingException - if the requested padding is not available

getInstance

public static final Cipher getInstance(String transformation,
                                       String provider)
                                throws NoSuchAlgorithmException,
                                       NoSuchProviderException,
                                       NoSuchPaddingException
Creates a Cipher object that implements the specified transformation, as supplied by the specified provider.
Parameters:
transformation - the string representation of the requested transformation, e.g., DES/CBC/PKCS5Padding
provider - the name of the cipher provider
Returns:
a cipher that implements the requested transformation
Throws:
NoSuchAlgorithmException - if the transformation is not available in the package supplied by the requested provider.
NoSuchProviderException - if the provider is not available in the environment.
NoSuchPaddingException - if the requested padding is not available
See Also:
Provider

getAlgorithm

public final String getAlgorithm()

Returns the algorithm name of this Cipher object.

This is the same name that was specified in one of the getInstance calls that created this Cipher object.

Returns:
the algorithm name of this Cipher object.

getProvider

public final Provider getProvider()
Returns the provider of this Cipher object.
Returns:
the provider of this Cipher object

init

public void init(int opmode,
                 Key key)
          throws InvalidKeyException

Initializes this cipher with a key. 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 a system-provided source of randomness. 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.

Parameters:
opmode - the operation mode of this cipher (this is either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher

init

public void init(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.

Parameters:
opmode - the operation mode of this cipher (this is either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
random - the source of randomness
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher

init

public void init(int opmode,
                 Key key,
                 AlgorithmParameterSpec params)
          throws InvalidKeyException,
                 InvalidAlgorithmParameterException

Initializes this cipher with a key and a set of algorithm parameters.

The cipher is initialized for encryption or decryption, depending on the value of opmode.

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 either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
params - the algorithm parameters
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher

init

public void init(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.

Parameters:
opmode - the operation mode of this cipher (this is either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
params - the algorithm parameters
random - 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

init

public void init(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.

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, and raise an InvalidAlgorithmParameterException if it is being initialized for decryption. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV).

If this cipher (including its underlying feedback or padding scheme) requires any random bytes (eg. 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 either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
params - the algorithm parameters
random - 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 is being initialized for decryption and requires algorithm parameters and params is null.

init

public void init(int opmode,
                 Key key,
                 AlgorithmParameters params)
          throws InvalidKeyException,
                 InvalidAlgorithmParameterException

Initializes this cipher with a key and a set of algorithm parameters.

The cipher is initialized for encryption or decryption, 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, and raise an InvalidAlgorithmParameterException if it is being initialized for decryption. The generated parameters can be retrieved using getParameters or getIV (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 using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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 either ENCRYPT_MODE or DECRYPT_MODE)
key - the key
params - the algorithm parameters
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 is being initialized for decryption and requires algorithm parameters and params is null.

getBlockSize

public int getBlockSize()
Returns the block size (in bytes).
Returns:
the block size (in bytes)

getOutputSize

public int getOutputSize(int inputLen)
                  throws IllegalStateException

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.

Parameters:
inputLen - - the input length (in bytes)
Returns:
the required output buffer size (in bytes)
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not yet been initialized)

getIV

public byte[] getIV()

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

This is useful in the case where a random IV has been created (see init), or 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.

update

public byte[] update(byte[] input)
              throws IllegalStateException

Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.

The bytes in the input buffer are processed, and the result is stored in a new buffer.

Parameters:
input - - the input buffer
Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)

update

public byte[] update(byte[] input,
                     int inputOffset,
                     int inputLen)
              throws IllegalStateException

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.

Parameters:
input - the input buffer
inputOffset - the offset in input where the input starts
inputLen - the input length
Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)

update

public int update(byte[] input,
                  int inputOffset,
                  int inputLen,
                  byte[] output)
           throws IllegalStateException,
                  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.

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.

Parameters:
input - the input buffer
inputOffset - the offset in input where the input starts
inputLen - the input length
output - the buffer for the result
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
ShortBufferException - if the given output buffer is too small to hold the result

update

public int update(byte[] input,
                  int inputOffset,
                  int inputLen,
                  byte[] output,
                  int outputOffset)
           throws IllegalStateException,
                  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.

Parameters:
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
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
ShortBufferException - if the given output buffer is too small to hold the result

doFinal

public byte[] doFinal()
               throws IllegalStateException,
                      IllegalBlockSizeException,
                      BadPaddingException

Finishes a multiple-part encryption or decryption operation, depending on how this cipher was initialized.

Input data that may have been buffered during a previous update operation is 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.

Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

doFinal

public byte[] doFinal(byte[] input)
               throws IllegalStateException,
                      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 bytes in the input buffer, 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.

Parameters:
input - the input buffer
Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

doFinal

public int doFinal(byte[] output,
                   int outputOffset)
            throws IllegalStateException,
                   IllegalBlockSizeException,
                   ShortBufferException,
                   BadPaddingException

Finishes a multiple-part encryption or decryption operation, depending on how this cipher was initialized.

Input data that may have been buffered during a previous update operation is 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. 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.

Parameters:
input - the input buffer
outputOffset - the offset in output where the result is stored
Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

doFinal

public byte[] doFinal(byte[] input,
                      int inputOffset,
                      int inputLen)
               throws IllegalStateException,
                      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.

Parameters:
input - the input buffer
inputOffset - the offset in input where the input starts
inputLen - the input length
Returns:
the new buffer with the result
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

doFinal

public int doFinal(byte[] input,
                   int inputOffset,
                   int inputLen,
                   byte[] output)
            throws IllegalStateException,
                   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.

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.

Parameters:
input - the input buffer
inputOffset - the offset in input where the input starts
inputLen - the input length
output - the buffer for the result
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

doFinal

public int doFinal(byte[] input,
                   int inputOffset,
                   int inputLen,
                   byte[] output,
                   int outputOffset)
            throws IllegalStateException,
                   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.

Parameters:
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
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this cipher is in a wrong state (e.g., has not been initialized)
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

getParameters

public final AlgorithmParameters getParameters()
Returns the parameters used with this cipher.

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).

Returns:
the parameters used with this cipher, or null if this cipher does not use any parameters.