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java.lang.Objectgnu.crypto.mode.BaseMode
gnu.crypto.mode.CTR
public class CTR
The implementation of the Counter Mode.
The algorithm steps are formally described as follows:
CTR Encryption: O[j] = E(K)(T[j]); for j = 1, 2...n; C[j] = P[j] ^ O[j]; for j = 1, 2...n. CTR Decryption: O[j] = E(K)(T[j]); for j = 1, 2...n; P[j] = C[j] ^ O[j]; for j = 1, 2...n.
where P
is the plaintext, C
is the ciphertext,
E(K)
is the underlying block cipher encryption function
parametrised with the session key K
, and T
is the
Counter.
This implementation, uses a standard incrementing function with a step of 1, and an initial value similar to that described in the NIST document.
References:
Field Summary |
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Fields inherited from class gnu.crypto.mode.BaseMode |
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cipher, cipherBlockSize, iv, lock, modeBlockSize, name, state |
Fields inherited from interface gnu.crypto.mode.IMode |
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DECRYPTION, ENCRYPTION, IV, MODE_BLOCK_SIZE, STATE |
Fields inherited from interface gnu.crypto.cipher.IBlockCipher |
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CIPHER_BLOCK_SIZE, KEY_MATERIAL |
Constructor Summary | |
---|---|
CTR(IBlockCipher underlyingCipher,
int cipherBlockSize)
Trivial package-private constructor for use by the Factory class. |
Method Summary | |
---|---|
Iterator |
blockSizes()
Returns an Iterator over the supported block sizes. |
Object |
clone()
Returns a clone of this instance. |
void |
decryptBlock(byte[] in,
int i,
byte[] out,
int o)
Decrypts exactly one block of ciphertext. |
void |
encryptBlock(byte[] in,
int i,
byte[] out,
int o)
Encrypts exactly one block of plaintext. |
void |
setup()
The initialisation phase of the concrete mode implementation. |
void |
teardown()
The termination phase of the concrete mode implementation. |
Methods inherited from class gnu.crypto.mode.BaseMode |
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currentBlockSize, defaultBlockSize, defaultKeySize, init, keySizes, name, reset, selfTest, update |
Methods inherited from class java.lang.Object |
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equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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CTR(IBlockCipher underlyingCipher, int cipherBlockSize)
Trivial package-private constructor for use by the Factory class.
underlyingCipher
- the underlying cipher implementation.cipherBlockSize
- the underlying cipher block size to use.Method Detail |
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public Object clone()
IBlockCipher
Returns a clone of this instance.
clone
in interface IBlockCipher
clone
in class BaseMode
public void setup()
BaseMode
setup
in class BaseMode
public void teardown()
BaseMode
teardown
in class BaseMode
public void encryptBlock(byte[] in, int i, byte[] out, int o)
IBlockCipher
Encrypts exactly one block of plaintext.
encryptBlock
in interface IBlockCipher
encryptBlock
in class BaseMode
in
- the plaintext.i
- index of in
from which to start considering
data.out
- the ciphertext.o
- index of out
from which to store result.public void decryptBlock(byte[] in, int i, byte[] out, int o)
IBlockCipher
Decrypts exactly one block of ciphertext.
decryptBlock
in interface IBlockCipher
decryptBlock
in class BaseMode
in
- the plaintext.i
- index of in
from which to start considering
data.out
- the ciphertext.o
- index of out
from which to store result.public Iterator blockSizes()
BaseMode
Returns an Iterator
over the supported block sizes. Each
element returned by this object is an Integer
.
The default behaviour is to return an iterator with just one value, which is that currently configured for the underlying block cipher. Concrete implementations may override this behaviour to signal their ability to support other values.
blockSizes
in interface IBlockCipher
blockSizes
in class BaseMode
Iterator
over the supported block sizes.
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