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SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object | +--gnu.crypto.mode.BaseMode | +--gnu.crypto.mode.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:
Fields inherited from class gnu.crypto.mode.BaseMode |
cipher, cipherBlockSize, iv, lock, modeBlockSize, name, state |
Fields inherited from interface gnu.crypto.mode.IMode |
DECRYPTION, ENCRYPTION, IV, MODE_BLOCK_SIZE, STATE |
Fields inherited from interface gnu.crypto.cipher.IBlockCipher |
CIPHER_BLOCK_SIZE, KEY_MATERIAL |
Constructor Summary | |
(package private) |
CTR(IBlockCipher underlyingCipher,
int cipherBlockSize)
Trivial package-private constructor for use by the Factory class. |
Method Summary | |
java.lang.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 |
blockSizes, currentBlockSize, defaultBlockSize, defaultKeySize, init, keySizes, name, reset, selfTest, update |
Methods inherited from class java.lang.Object |
|
Constructor Detail |
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 |
public java.lang.Object clone()
IBlockCipher
Returns a clone of this instance.
clone
in class BaseMode
gnu.crypto.cipher.IBlockCipher
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 class BaseMode
gnu.crypto.cipher.IBlockCipher
in
- the plaintext.inOffset
- index of in
from which to start considering
data.out
- the ciphertext.outOffset
- index of out
from which to store result.java.lang.IllegalStateException
- if the instance is not initialised.public void decryptBlock(byte[] in, int i, byte[] out, int o)
IBlockCipher
Decrypts exactly one block of ciphertext.
decryptBlock
in class BaseMode
gnu.crypto.cipher.IBlockCipher
in
- the plaintext.inOffset
- index of in
from which to start considering
data.out
- the ciphertext.outOffset
- index of out
from which to store result.java.lang.IllegalStateException
- if the instance is not initialised.
|
For the latest news and information visit The GNU Crypto project |
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