package ch.ethz.ssh2.crypto;
import ch.ethz.ssh2.crypto.digest.HashForSSH2Types;
import java.math.BigInteger;
/**
* Establishes key material for iv/key/mac (both directions).
*
* @author Christian Plattner, plattner@inf.ethz.ch
* @version $Id: KeyMaterial.java,v 1.2 2005/12/05 17:13:27 cplattne Exp $
*/
public class KeyMaterial
{
public byte[] initial_iv_client_to_server;
public byte[] initial_iv_server_to_client;
public byte[] enc_key_client_to_server;
public byte[] enc_key_server_to_client;
public byte[] integrity_key_client_to_server;
public byte[] integrity_key_server_to_client;
private static byte[] calculateKey(HashForSSH2Types sh, BigInteger K, byte[] H, byte type, byte[] SessionID,
int keyLength)
{
byte[] res = new byte[keyLength];
int dglen = sh.getDigestLength();
int numRounds = (keyLength + dglen - 1) / dglen;
byte[][] tmp = new byte[numRounds][];
sh.reset();
sh.updateBigInt(K);
sh.updateBytes(H);
sh.updateByte(type);
sh.updateBytes(SessionID);
tmp[0] = sh.getDigest();
int off = 0;
int produced = Math.min(dglen, keyLength);
System.arraycopy(tmp[0], 0, res, off, produced);
keyLength -= produced;
off += produced;
for (int i = 1; i < numRounds; i++)
{
sh.updateBigInt(K);
sh.updateBytes(H);
for (int j = 0; j < i; j++)
sh.updateBytes(tmp[j]);
tmp[i] = sh.getDigest();
produced = Math.min(dglen, keyLength);
System.arraycopy(tmp[i], 0, res, off, produced);
keyLength -= produced;
off += produced;
}
return res;
}
public static KeyMaterial create(String hashType, byte[] H, BigInteger K, byte[] SessionID, int keyLengthCS,
int blockSizeCS, int macLengthCS, int keyLengthSC, int blockSizeSC, int macLengthSC)
throws IllegalArgumentException
{
KeyMaterial km = new KeyMaterial();
HashForSSH2Types sh = new HashForSSH2Types(hashType);
km.initial_iv_client_to_server = calculateKey(sh, K, H, (byte) 'A', SessionID, blockSizeCS);
km.initial_iv_server_to_client = calculateKey(sh, K, H, (byte) 'B', SessionID, blockSizeSC);
km.enc_key_client_to_server = calculateKey(sh, K, H, (byte) 'C', SessionID, keyLengthCS);
km.enc_key_server_to_client = calculateKey(sh, K, H, (byte) 'D', SessionID, keyLengthSC);
km.integrity_key_client_to_server = calculateKey(sh, K, H, (byte) 'E', SessionID, macLengthCS);
km.integrity_key_server_to_client = calculateKey(sh, K, H, (byte) 'F', SessionID, macLengthSC);
return km;
}
}