shs.java

JAVA的加密源程序

/*
Christoforos Pirillos @ Villanova University - May 1999
based on code from the book "Java Network Programming" by Hughes
*/

package encryption;

/** Provides integrity checking on any streams-based communications
channel*/

public class SHS extends Hash {

/**Returns a digest of the specified byte array. The digest is computed
from len bytes of the array, starting from index off*/

public byte[] digest (byte[] text, int off, int len) {
	byte[] message = pad (text, off, len);
	int[] data = new int[80];
	int[] digest = { h0,h1,h2,h3,h4};

	for (int i=0; i<message.length; i +=64) {
	 Crypt.bytesToInts (message, i, data, 0, 16) ;
	 transform (digest, data);
	}

	byte[] result = new byte[20];
	Crypt.intsToBytes (digest, 0, 5, result, 0);
	return result;
}

protected static final int h0 = 0x67452301;
protected static final int h1 = 0xEFCDAB89;
protected static final int h2 = 0x98BADCFE;
protected static final int h3 = 0x10325476;
protected static final int h4 = 0xC3D2E1F0;

/**Pads the specified text to be a multiple of the hash block size*/

protected byte[] pad (byte[] text, int off, int len) {

	int padLen = (len + 9 + 63) & ~63;
	byte[] paddedText = new byte[padLen];
	System.arraycopy (text, off, paddedText, 0, len);	
	paddedText[len] = (byte) 0x80;
	Crypt.longToBytes ((long) len << 3, paddedText, padLen -8);
	return paddedText;
}

/**Performs the body of the SHA digest. Expands the 16 int values in the
data array into 80 by applying various XOR and shift operations.
NOTE: this class contains some corrections and it provides different
results than the original implementation, so the original test cases do
apply here.*/

protected final void transform (int[] digest, int[] data) {

	int a = digest[0];
	int b = digest[1];
	int c = digest[2];
	int d = digest[3];
	int e = digest[4];

for (int i=16; i<80; ++i) {
	int tmp = data[i-3]^data[i-8]^data[i-14]^data[i-16];
	data[i] = (tmp<<1) | (tmp >>>31);
}

for (int i=0;i<80;++i) {
	int temp = ((a<<5) | (a>>>27)) + e +data[i];
	if (i<20)
		temp += ((b&c) | (~b & d))+k1;
	else if (i<40)
		temp+=(b^c^d)+k2;
	else if (i<60)
		temp+=((b&c) | (b&d) | (c&d))+k3;
	else 
		temp+=(b^c^d)+k4;
	e=d;
	d=c;
	c=((b<<30) | (b>>>2));
	b=a;
	a=temp;
}

digest[0]+=a;
digest[1]+=b;
digest[2]+=c;
digest[3]+=d;
digest[4]+=e;

}

protected static final int k1=0x5A827999;
protected static final int k2=0x6ED9EBA1;
protected static final int k3=0x8F1BBCDC;
protected static final int k4=0xCA62C1D6;

/**This algorithm produces a 160-bit digest or 20 bytes. This returns the
number of bytes used*/

public int digestSize () {
 return 20;
}


} /*end of class SHS */