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/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");

Using modes such as `CFB` and `OFB`, block ciphers can encrypt data in units smaller than the cipher's actual block size. When requesting such a mode, you may optionally specify the number of bits to be processed at a time by appending this number to the mode name as shown in the "`DES/CFB8/NoPadding`" and "`DES/OFB32/PKCS5Padding`" transformations. If no such number is specified, a provider-specific default is used. (For example, the SunJCE provider uses a default of 64 bits for DES.) Thus, block ciphers can be turned into byte-oriented stream ciphers by using an 8 bit mode such as CFB8 or OFB8.``

Since:
  1.4
See Also:
  `KeyGenerator`, `SecretKey`

### Field Summary

Fields
`static int` `DECRYPT_MODE` Constant used to initialize cipher to decryption mode.
`static int` `ENCRYPT_MODE` Constant used to initialize cipher to encryption mode.
`static int` `PRIVATE_KEY` Constant used to indicate the to-be-unwrapped key is a "private key".
`static int` `PUBLIC_KEY` Constant used to indicate the to-be-unwrapped key is a "public key".
`static int` `SECRET_KEY` Constant used to indicate the to-be-unwrapped key is a "secret key".
`static int` `UNWRAP_MODE` Constant used to initialize cipher to key-unwrapping mode.
`static int` `WRAP_MODE` Constant used to initialize cipher to key-wrapping mode.

### Constructor Summary

Constructors
`protected` `Cipher(CipherSpi cipherSpi, Provider provider, String transformation)` Creates a Cipher object.

### Method Summary

Methods
`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.
`int` `doFinal(ByteBuffer input, ByteBuffer output)` 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).
`ExemptionMechanism` `getExemptionMechanism()` Returns the exemption mechanism object used with this cipher.
`static Cipher` `getInstance(String transformation)` Returns a `Cipher` object that implements the specified transformation.
`static Cipher` `getInstance(String transformation, Provider provider)` Returns a `Cipher` object that implements the specified transformation.
`static Cipher` `getInstance(String transformation, String provider)` Returns a `Cipher` object that implements the specified transformation.
`byte[]` `getIV()` Returns the initialization vector (IV) in a new buffer.
`static int` `getMaxAllowedKeyLength(String transformation)` Returns the maximum key length for the specified transformation according to the installed JCE jurisdiction policy files.
`static AlgorithmParameterSpec` `getMaxAllowedParameterSpec(String transformation)` Returns an AlgorithmParameterSpec object which contains the maximum cipher parameter value according to the jurisdiction policy file.
`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, Certificate certificate)` Initializes this cipher with the public key from the given certificate.
`void` `init(int opmode, Certificate certificate, SecureRandom random)` Initializes this cipher with the public key from the given certificate and a source of randomness.
`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.
`Key` `unwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType)` Unwrap a previously wrapped key.
`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.
`int` `update(ByteBuffer input, ByteBuffer output)` Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
`byte[]` `wrap(Key key)` Wrap a key.

### 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

Constant used to initialize cipher to encryption mode.

See Also:
  Constant Field Values

#### DECRYPT_MODE

    public static final int DECRYPT_MODE

Constant used to initialize cipher to decryption mode.

See Also:
  Constant Field Values

#### WRAP_MODE

    public static final int WRAP_MODE

Constant used to initialize cipher to key-wrapping mode.

See Also:
  Constant Field Values

#### UNWRAP_MODE

    public static final int UNWRAP_MODE

Constant used to initialize cipher to key-unwrapping mode.

See Also:
  Constant Field Values

#### PUBLIC_KEY

    public static final int PUBLIC_KEY

Constant used to indicate the to-be-unwrapped key is a "public key".

See Also:
  Constant Field Values

#### PRIVATE_KEY

    public static final int PRIVATE_KEY

Constant used to indicate the to-be-unwrapped key is a "private key".

See Also:
  Constant Field Values

#### SECRET_KEY

    public static final int SECRET_KEY

Constant used to indicate the to-be-unwrapped key is a "secret key".

See Also:
  Constant Field Values

### 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

Returns a `Cipher` object that implements the specified transformation.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new Cipher object encapsulating the CipherSpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the `Security.getProviders()` method.

Parameters:
  `transformation` - the name of the transformation, e.g., DES/CBC/PKCS5Padding. See Appendix A in the Java Cryptography Architecture Reference Guide for information about standard transformation names.
Returns:
  a cipher that implements the requested transformation.
Throws:
  `NoSuchAlgorithmException` - if `transformation` is null, empty, in an invalid format, or if no Provider supports a CipherSpi implementation for the specified algorithm.
  `NoSuchPaddingException` - if `transformation` contains a padding scheme that is not available.
See Also:
  `Provider`

#### getInstance

    public static final Cipher getInstance(String transformation,
                     String provider)
                                    throws NoSuchAlgorithmException,
                                           NoSuchProviderException,
                                           NoSuchPaddingException

Returns a `Cipher` object that implements the specified transformation.

A new Cipher object encapsulating the CipherSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the `Security.getProviders()` method.

Parameters:
  `transformation` - the name of the transformation, e.g., DES/CBC/PKCS5Padding. See Appendix A in the Java Cryptography Architecture Reference Guide for information about standard transformation names.
  `provider` - the name of the provider.
Returns:
  a cipher that implements the requested transformation.
Throws:
  `NoSuchAlgorithmException` - if `transformation` is null, empty, in an invalid format, or if a CipherSpi implementation for the specified algorithm is not available from the specified provider.
  `NoSuchProviderException` - if the specified provider is not registered in the security provider list.
  `NoSuchPaddingException` - if `transformation` contains a padding scheme that is not available.
  `IllegalArgumentException` - if the `provider` is null or empty.
See Also:
  `Provider`

#### getInstance

    public static final Cipher getInstance(String transformation,
                     Provider provider)
                                    throws NoSuchAlgorithmException,
                                           NoSuchPaddingException

Returns a `Cipher` object that implements the specified transformation.

A new Cipher object encapsulating the CipherSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

Parameters:
  `transformation` - the name of the transformation, e.g., DES/CBC/PKCS5Padding. See Appendix A in the Java Cryptography Architecture Reference Guide for information about standard transformation names.
  `provider` - the provider.
Returns:
  a cipher that implements the requested transformation.
Throws:
  `NoSuchAlgorithmException` - if `transformation` is null, empty, in an invalid format, or if a CipherSpi implementation for the specified algorithm is not available from the specified Provider object.
  `NoSuchPaddingException` - if `transformation` contains a padding scheme that is not available.
  `IllegalArgumentException` - if the `provider` is null.
See Also:
  `Provider`

#### getProvider

    public final Provider getProvider()

Returns the provider of this `Cipher` object.

Returns:
  the provider of this `Cipher` object

#### 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.

#### getBlockSize

    public final int getBlockSize()

Returns the block size (in bytes).

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

#### getOutputSize

    public final 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).

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 final byte[] getIV()

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

This is useful in the case where a random IV was created, or in the context of password-based encryption or decryption, where the IV is derived from a user-supplied password.

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.

#### 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 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.

#### getExemptionMechanism

    public final ExemptionMechanism getExemptionMechanism()

Returns the exemption mechanism object used with this cipher.

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

#### init

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

Initializes this cipher with a key.

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 `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 one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`)
  `key` - the key
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or if this cipher is being initialized for decryption and requires algorithm parameters that cannot be determined from the given key, or if the given key has a keysize that exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).

#### init

    public final 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 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 `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 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_MODE` or `UNWRAP_MODE`)
  `key` - the encryption key
  `random` - the source of randomness
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or if this cipher is being initialized for decryption and requires algorithm parameters that cannot be determined from the given key, or if the given key has a keysize that exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).

#### init

    public final 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 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 `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 one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`)
  `key` - the encryption key
  `params` - the algorithm parameters
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).
  `InvalidAlgorithmParameterException` - if the given algorithm parameters are inappropriate for this cipher, or this cipher is being initialized for decryption and requires algorithm parameters and `params` is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files).

#### init

    public final 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 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 `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 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_MODE` or `UNWRAP_MODE`)
  `key` - the encryption key
  `params` - the algorithm parameters
  `random` - the source of randomness
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).
  `InvalidAlgorithmParameterException` - if the given algorithm parameters are inappropriate for this cipher, or this cipher is being initialized for decryption and requires algorithm parameters and `params` is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files).

#### init

    public final 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 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 `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 one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`)
  `key` - the encryption key
  `params` - the algorithm parameters
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).
  `InvalidAlgorithmParameterException` - if the given algorithm parameters are inappropriate for this cipher, or this cipher is being initialized for decryption and requires algorithm parameters and `params` is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files).

#### init

    public final 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 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 `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 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_MODE` or `UNWRAP_MODE`)
  `key` - the encryption key
  `params` - the algorithm parameters
  `random` - the source of randomness
Throws:
  `InvalidKeyException` - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).
  `InvalidAlgorithmParameterException` - if the given algorithm parameters are inappropriate for this cipher, or this cipher is being initialized for decryption and requires algorithm parameters and `params` is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files).

#### init

    public final void init(int opmode,
            Certificate certificate)
                    throws InvalidKeyException

Initializes this cipher with the public key from the given certificate.

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 the certificate is of type X.509 and has a key usage extension field marked as critical, and the value of the key usage extension field implies that the public key in the certificate and its corresponding private key are not supposed to be used for the operation represented by the value of `opmode`, an `InvalidKeyException` is thrown.

If this cipher requires any algorithm parameters that cannot be derived from the public key in the given certificate, the underlying cipher implementation is supposed to generate the required parameters itself (using provider-specific default or ramdom 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 `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 one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`)
  `certificate` - the certificate
Throws:
  `InvalidKeyException` - if the public key in the given certificate is inappropriate for initializing this cipher, or this cipher is being initialized for decryption or unwrapping keys and requires algorithm parameters that cannot be determined from the public key in the given certificate, or the keysize of the public key in the given certificate has a keysize that exceeds the maximum allowable keysize (as determined by the configured jurisdiction policy files).

#### init

    public final void init(int opmode,
            Certificate certificate,
            SecureRandom random)
                    throws InvalidKeyException

Initializes this cipher with the public key from the given certificate 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 the certificate is of type X.509 and has a key usage extension field marked as critical, and the value of the key usage extension field implies that the public key in the certificate and its corresponding private key are not supposed to be used for the operation represented by the value of `opmode`, an `InvalidKeyException` is thrown.

If this cipher requires any algorithm parameters that cannot be derived from the public key in the given `certificate`, 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 `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 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_MODE` or `UNWRAP_MODE`)
  `certificate` - the certificate
  `random` - the source of randomness
Throws:
  `InvalidKeyException` - if the public key in the given certificate is inappropriate for initializing this cipher, or this cipher is being initialized for decryption or unwrapping keys and requires algorithm parameters that cannot be determined from the public key in the given certificate, or the keysize of the public key in the given certificate has a keysize that exceeds the maximum allowable keysize (as determined by the configured jurisdiction policy files).

#### update

    public final byte[] update(byte[] input)

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.

If `input` has a length of zero, this method returns `null`.

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

#### update

    public final 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.

The first `inputLen` bytes in the `input` buffer, starting at `inputOffset` inclusive, are processed, and the result is stored in a new buffer.

If `inputLen` is zero, this method returns `null`.

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, or null if the underlying cipher is a block cipher and the input data is too short to result in a new block.
Throws:
  `IllegalStateException` - if this cipher is in a wrong state (e.g., has not been initialized)

#### update

    public final int update(byte[] input,
             int inputOffset,
             int inputLen,
             byte[] output)
                     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` inclusive, 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.

If `inputLen` is zero, this method returns a length of zero.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same byte array and no unprocessed input data is overwritten when the result is copied into the output buffer.

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 final int update(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` 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. In this case, repeat this call with a larger output buffer. Use `getOutputSize` to determine how big the output buffer should be.

If `inputLen` is zero, this method returns a length of zero.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same byte array and no unprocessed input data is overwritten when the result is copied into the output buffer.

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

#### update

    public final int update(ByteBuffer input,
             ByteBuffer output)
                     throws ShortBufferException

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. In this case, repeat this call with a larger output buffer. Use `getOutputSize` to determine how big the output buffer should be.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same block of memory and no unprocessed input data is overwritten when the result is copied into the output buffer.

Parameters:
  `input` - the input ByteBuffer
  `output` - the output ByteByffer
Returns:
  the number of bytes stored in `output`
Throws:
  `IllegalStateException` - if this cipher is in a wrong state (e.g., has not been initialized)
  `IllegalArgumentException` - if input and output are the same object
  `ReadOnlyBufferException` - if the output buffer is read-only
  `ShortBufferException` - if there is insufficient space in the output buffer
Since:
  1.5

#### doFinal

    public final byte[] doFinal()
                         throws 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.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

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; 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

#### doFinal

    public final int doFinal(byte[] output,
              int outputOffset)
                      throws 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 the `output` buffer, starting at `outputOffset` inclusive.

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.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Parameters:
  `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; 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

#### doFinal

    public final byte[] doFinal(byte[] input)
                         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 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.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

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; 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

#### doFinal

    public final byte[] doFinal(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` inclusive, and any input bytes that may have been buffered during a previous `update` operation, are processed, with padding (if requested) being applied. The result is stored in a new buffer.

Upon finishing, this method resets this cipher object to the state it was in when previously initialized via a call to `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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

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; 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

#### doFinal

    public final int doFinal(byte[] input,
              int inputOffset,
              int inputLen,
              byte[] 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.

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. 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.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same byte array and no unprocessed input data is overwritten when the result is copied into the output buffer.

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; 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

#### doFinal

    public final int doFinal(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` inclusive, and any input bytes that may have been buffered during a previous `update` operation, are processed, with padding (if requested) being applied. The result is stored in the `output` buffer, starting at `outputOffset` inclusive.

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.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same byte array and no unprocessed input data is overwritten when the result is copied into the output buffer.

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; 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

#### doFinal

    public final int doFinal(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 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. In this case, repeat this call with a larger output buffer. Use `getOutputSize` to determine how big the output buffer should be.

Upon finishing, 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.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Note: this method should be copy-safe, which means the `input` and `output` buffers can reference the same byte array and no unprocessed input data is overwritten when the result is copied into the output buffer.

Parameters:
  `input` - the input ByteBuffer
  `output` - the output ByteBuffer
Returns:
  the number of bytes stored in `output`
Throws:
  `IllegalStateException` - if this cipher is in a wrong state (e.g., has not been initialized)
  `IllegalArgumentException` - if input and output are the same object
  `ReadOnlyBufferException` - if the output buffer is read-only
  `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
Since:
  1.5

#### wrap

    public final byte[] wrap(Key key)
                      throws IllegalBlockSizeException,
                             InvalidKeyException

Wrap a key.

Parameters:
  `key` - the key to be wrapped.
Returns:
  the wrapped key.
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, 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).

#### unwrap

    public final Key unwrap(byte[] wrappedKey,
             String wrappedKeyAlgorithm,
             int wrappedKeyType)
                     throws InvalidKeyException,
                            NoSuchAlgorithmException

Unwrap a previously wrapped key.

Parameters:
  `wrappedKey` - the key to be unwrapped.
  `wrappedKeyAlgorithm` - the algorithm associated with the wrapped key.
  `wrappedKeyType` - the type of the wrapped key. This must be one of `SECRET_KEY`, `PRIVATE_KEY`, or `PUBLIC_KEY`.
Returns:
  the unwrapped key.
Throws:
  `IllegalStateException` - if this cipher is in a wrong state (e.g., has not been initialized).
  `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`.

#### getMaxAllowedKeyLength

    public static final int getMaxAllowedKeyLength(String transformation)
                                            throws NoSuchAlgorithmException

Returns the maximum key length for the specified transformation according to the installed JCE jurisdiction policy files. If JCE unlimited strength jurisdiction policy files are installed, Integer.MAX_VALUE will be returned. For more information on default key size in JCE jurisdiction policy files, please see Appendix E in the Java Cryptography Architecture Reference Guide.

Parameters:
  `transformation` - the cipher transformation.
Returns:
  the maximum key length in bits or Integer.MAX_VALUE.
Throws:
  `NullPointerException` - if `transformation` is null.
  `NoSuchAlgorithmException` - if `transformation` is not a valid transformation, i.e. in the form of "algorithm" or "algorithm/mode/padding".
Since:
  1.5

#### getMaxAllowedParameterSpec

    public static final AlgorithmParameterSpec getMaxAllowedParameterSpec(String transformation)
                                                                   throws NoSuchAlgorithmException

Returns an AlgorithmParameterSpec object which contains the maximum cipher parameter value according to the jurisdiction policy file. If JCE unlimited strength jurisdiction policy files are installed or there is no maximum limit on the parameters for the specified transformation in the policy file, null will be returned.

Parameters:
  `transformation` - the cipher transformation.
Returns:
  an AlgorithmParameterSpec which holds the maximum value or null.
Throws:
  `NullPointerException` - if `transformation` is null.
  `NoSuchAlgorithmException` - if `transformation` is not a valid transformation, i.e. in the form of "algorithm" or "algorithm/mode/padding".
Since:
  1.5

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