gnu.crypto.prng
public class ICMGenerator extends BasePRNG implements Cloneable
Counter Mode is a way to define a pseudorandom keystream generator using a block cipher. The keystream can be used for additive encryption, key derivation, or any other application requiring pseudorandom data.
In ICM, the keystream is logically broken into segments. Each segment is identified with a segment index, and the segments have equal lengths. This segmentation makes ICM especially appropriate for securing packet-based protocols.
This implementation adheres to the definition of the ICM keystream
generation function that allows for any symetric key block cipher algorithm
(initialisation parameter gnu.crypto.prng.icm.cipher.name
taken
to be an instance of java.lang.String) to be used. If such a
parameter is not defined/included in the initialisation Map
,
then the "Rijndael" algorithm is used. Furthermore, if the initialisation
parameter gnu.crypto.cipher.block.size
(taken to be a instance
of java.lang.Integer) is missing or undefined in the initialisation
Map
, then the cipher's default block size is used.
The practical limits and constraints of such generator are:
256 ** BLOCK_INDEX_LENGTH
. The number of segments MUST NOT
exceed 256 ** SEGMENT_INDEX_LENGTH
. These restrictions ensure
the uniqueness of each block cipher input.SEGMENT_LENGTH
octets; this value
MUST NOT exceed the value (256 ** BLOCK_INDEX_LENGTH) *
BLOCK_LENGTH
.SEGMENT_INDEX_LENGTH
and
BLOCK_INDEX_LENGTH
MUST NOT exceed BLOCK_LENGTH
/ 2
. This requirement protects the ICM keystream generator from
potentially failing to be pseudorandom.NOTE: Rijndael is used as the default symmetric key block cipher algorithm because, with its default block and key sizes, it is the AES. Yet being Rijndael, the algorithm offers more versatile block and key sizes which may prove to be useful for generating longer key streams.
References:
Version: $Revision: 1.13 $
Field Summary | |
---|---|
static String | BLOCK_INDEX_LENGTH Property name of ICM's block index length. |
static String | CIPHER Property name of underlying block cipher for this ICM generator. |
static String | OFFSET Property name of ICM's offset. |
static String | SEGMENT_INDEX Property name of ICM's segment index. |
static String | SEGMENT_INDEX_LENGTH Property name of ICM's segment index length. |
Constructor Summary | |
---|---|
ICMGenerator() Trivial 0-arguments constructor. |
Method Summary | |
---|---|
void | fillBlock() |
void | setup(Map attributes) |