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java.lang.Object | +----javax.crypto.Cipher
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, provider-specific defaults are used for mode and padding). For example, "DES/CBC/PKCS5Padding" represents a valid transformation.
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 Sun JCE provider uses a default of 64 bits.)
Cipher object that implements the specified
transformation, as supplied by the default provider.
Cipher object that implements the specified
transformation, as supplied by the specified provider.
update or
doFinal operation, given the input length
inputLen (in bytes).
Cipher object.
public static final int ENCRYPT_MODE
public static final int DECRYPT_MODE
protected Cipher(CipherSpi cipherSpi,
Provider provider,
String transformation)
public static final Cipher getInstance(String transformation) throws NoSuchAlgorithmException, NoSuchPaddingException
Cipher object that implements the specified
transformation, as supplied by the default provider.
public static final Cipher getInstance(String transformation,
String provider) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException
Cipher object that implements the specified
transformation, as supplied by the specified provider.
public final Provider getProvider()
Cipher object.
Cipher object
public final int getBlockSize()
public final int getOutputSize(int inputLen) throws IllegalStateException
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.
public final byte[] getIV()
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.
public final void init(int opmode,
Key key) throws InvalidKeyException
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.
ENCRYPT_MODE or DECRYPT_MODE)
public final void init(int opmode,
Key key,
SecureRandom random) throws InvalidKeyException
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.
ENCRYPT_MODE or DECRYPT_MODE)
public final void init(int opmode,
Key key,
AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
ENCRYPT_MODE or DECRYPT_MODE)
public final void init(int opmode,
Key key,
AlgorithmParameterSpec params,
SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
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.
ENCRYPT_MODE or DECRYPT_MODE)
public final byte[] update(byte input[]) throws IllegalStateException
The bytes in the input buffer are processed, and the
result is stored in a new buffer.
public final byte[] update(byte input[],
int inputOffset,
int inputLen) throws IllegalStateException
The first inputLen bytes in the input
buffer, starting at inputOffset, are processed, and the
result is stored in a new buffer.
input where the input
starts
public final int update(byte input[],
int inputOffset,
int inputLen,
byte output[]) throws IllegalStateException, ShortBufferException
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.
input where the input
starts
output
public final int update(byte input[],
int inputOffset,
int inputLen,
byte output[],
int outputOffset) throws IllegalStateException, ShortBufferException
The first inputLen bytes in the input
buffer, starting at inputOffset, are processed, and the
result is stored in the output buffer, starting at
outputOffset.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this
call with a larger output buffer. Use
getOutputSize to determine how big the
output buffer should be.
input where the input
starts
output where the result
is stored
output
public final byte[] doFinal() throws IllegalStateException, 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.
public final int doFinal(byte output[],
int outputOffset) throws IllegalStateException, 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.
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.
output where the result
is stored
output
public final byte[] doFinal(byte input[]) throws IllegalStateException, 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.
public final byte[] doFinal(byte input[],
int inputOffset,
int inputLen) throws IllegalStateException, IllegalBlockSizeException, BadPaddingException
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.
input where the input
starts
public final int doFinal(byte input[],
int inputOffset,
int inputLen,
byte output[]) throws IllegalStateException, ShortBufferException, IllegalBlockSizeException, BadPaddingException
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.
input where the input
starts
output
public final int doFinal(byte input[],
int inputOffset,
int inputLen,
byte output[],
int outputOffset) throws IllegalStateException, ShortBufferException, IllegalBlockSizeException, BadPaddingException
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.
input where the input
starts
output where the result
is stored
output
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