java.lang.Object javax.crypto.Cipher
public class Cipher
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:
(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.
When requesting a block cipher in stream cipher mode (e.g., DES in CFB or OFB mode), the user 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.)
Field Summary | |
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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 | |
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protected |
Cipher
(
CipherSpi
cipherSpi,
Provider
provider,
String
transformation) Creates a Cipher object. |
Method Summary | |
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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
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 |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Field Detail |
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public static final int ENCRYPT_MODE
public static final int DECRYPT_MODE
public static final int WRAP_MODE
public static final int UNWRAP_MODE
public static final int PUBLIC_KEY
public static final int PRIVATE_KEY
public static final int SECRET_KEY
Constructor Detail |
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protected Cipher(CipherSpi cipherSpi, Provider provider, String transformation)
Method Detail |
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public static final Cipher getInstance(String transformation) throws NoSuchAlgorithmException, NoSuchPaddingException
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.
public static final Cipher getInstance(String transformation, String provider) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException
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.
public static final Cipher getInstance(String transformation, Provider provider) throws NoSuchAlgorithmException, NoSuchPaddingException
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.
public final Provider getProvider()
public final String getAlgorithm()
This is the same name that was specified in one of the getInstance calls that created this Cipher object..
public final int getBlockSize()
public final int getOutputSize(int inputLen)
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.
public final byte[] getIV()
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.
public final AlgorithmParameters getParameters()
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.
public final ExemptionMechanism getExemptionMechanism()
public final void init(int opmode, Key key) throws InvalidKeyException
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.
public final void init(int opmode, Key key, SecureRandom random) throws InvalidKeyException
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.
public final void init(int opmode, Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
public final void init(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
public final void init(int opmode, Key key, AlgorithmParameters params) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
public final void init(int opmode, Key key, AlgorithmParameters params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
public final void init(int opmode, Certificate certificate) throws InvalidKeyException
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.
public final void init(int opmode, Certificate certificate, SecureRandom random) throws InvalidKeyException
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.
public final byte[] update(byte[] input)
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.
public final byte[] update(byte[] input, int inputOffset, int inputLen)
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.
public final int update(byte[] input, int inputOffset, int inputLen, byte[] output) throws ShortBufferException
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.
public final int update(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException
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.
public final int update(ByteBuffer input, ByteBuffer output) throws ShortBufferException
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.
public final byte[] doFinal() throws IllegalBlockSizeException, BadPaddingException
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.
public final int doFinal(byte[] output, int outputOffset) throws IllegalBlockSizeException, ShortBufferException, BadPaddingException
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.
public final byte[] doFinal(byte[] input) throws IllegalBlockSizeException, BadPaddingException
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.
public final byte[] doFinal(byte[] input, int inputOffset, int inputLen) throws IllegalBlockSizeException, BadPaddingException
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.
public final int doFinal(byte[] input, int inputOffset, int inputLen, byte[] output) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException
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.
public final int doFinal(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException
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.
public final int doFinal(ByteBuffer input, ByteBuffer output) throws ShortBufferException, IllegalBlockSizeException, BadPaddingException
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.
public final byte[] wrap(Key key) throws IllegalBlockSizeException, InvalidKeyException
public final Key unwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType) throws InvalidKeyException, NoSuchAlgorithmException
public static final int getMaxAllowedKeyLength(String transformation) throws NoSuchAlgorithmException
public static final AlgorithmParameterSpec getMaxAllowedParameterSpec(String transformation) throws NoSuchAlgorithmException