Rabbit流密码是由Cryptico公司（http://www.cryptico.com）设计的，密钥长度128位，
最大加密消息长度为264 Bytes，即16 TB，若消息超过该长度，则需要更换密钥对剩下的消息进行处理。它是目前安全性较高，加/解密速度比较高效的流密码之一，在各种处理器平台上都有不凡的表现。
详细资料：
1.http://www.cryptico.com/Files/filer/rabbit_fse.pdf
2.http://www.ietf.org/rfc/rfc4503.txt
本文实现了该算法的java语言实现，仅供参考。
2. 实现源码
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/**
* The Java Implementation of Rabbit Stream Cipher
* @author cnbragon
* @email cnbragon_dot_163_dot_com
* @date 2009/09/25
* @note Not implemented IV scheme
* @Reference:
* 1.http://www.cryptico.com/Files/filer/rabbit_fse.pdf * 2.http://www.ietf.org/rfc/rfc4503.txt
*/
class Rabbit
{
private int[] x = new int[8];
private int[] c = new int[8];
private int carry;
public void Rabbit()
{
for(int i = 0; i < 8; i++)
{
x[i] = c[i] = 0;
}
carry = 0;
}
private int g_func(int x)
{
int a = x & 0xffff;
int b = x >>> 16;
int h =( ( ( ( a * a ) >>> 17 ) + ( a * b ) ) >>> 15 ) + b * b;
int l = x * x;
return h ^ l;
}
/**
* @declaration 比较两个无符号整数的十六进制的大小，即作为无符号整数进行比较
* @param x
* @param y
* @return 若(unsigned x) < (unsigned y)，则返回1，否则返回0
*/
private int compare(int x, int y)
{
long a = x;
long b = y;
a &= 0x00000000ffffffffl;
b &= 0x00000000ffffffffl;
return (a < b) ? 1 : 0;
}
private int rotL(int x, int y)
{
return ( x << y ) | ( x >>> (32 - y) );
}
private void next_state()
{
int[] g = new int[8];
int[] c_old = new int[8];
int i = 0;
for( i = 0; i < 8; i++)
{
c_old[i] = c[i];
}
c[0] += 0x4d34d34d + carry;
c[1] += 0xd34d34d3 + compare(c[0], c_old[0]); c[2] += 0x34d34d34 + compare(c[1], c_old[1]); c[3] += 0x4d34d34d + compare(c[2], c_old[2]); c[4] += 0xd34d34d3 + compare(c[3], c_old[3]); c[5] += 0x34d34d34 + compare(c[4], c_old[4]); c[6] += 0x4d34d34d + compare(c[5], c_old[5]); c[7] += 0xd34d34d3 + compare(c[6], c_old[6]); carry = compare(c[7], c_old[7]);
for( i = 0; i < 8; i++)
{
g[i] = g_func(x[i] + c[i]);
}
x[0] = g[0] + rotL(g[7], 16) + rotL(g[6], 16); x[1] = g[1] + rotL(g[0], 8 ) + g[7]; x[2] = g[2] + rotL(g[1], 16) + rotL(g[0], 16); x[3] = g[3] + rotL(g[2], 8 ) + g[1]; x[4] = g[4] + rotL(g[3], 16) + rotL(g[2], 16); x[5] = g[5] + rotL(g[4], 8 ) + g[3]; x[6] = g[6] + rotL(g[5], 16) + rotL(g[4], 16); x[7] = g[7] + rotL(g[6], 8 ) + g[5];
}
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