package ch.ethz.ssh2.crypto.dh;
import java.math.BigInteger;
import java.security.SecureRandom;
import ch.ethz.ssh2.crypto.digest.HashForSSH2Types;
import ch.ethz.ssh2.log.Logger;
/**
* DhExchange.
*
* @author Christian Plattner, plattner@inf.ethz.ch
* @version $Id: DhExchange.java,v 1.5 2006/02/14 19:43:15 cplattne Exp $
*/
public class DhExchange
{
private static final Logger log = Logger.getLogger(DhExchange.class);
/* Given by the standard */
static final BigInteger p1, p14;
static final BigInteger g;
BigInteger p;
/* Client public and private */
BigInteger e;
BigInteger x;
/* Server public */
BigInteger f;
/* Shared secret */
BigInteger k;
static
{
final String p1_string = "17976931348623159077083915679378745319786029604875"
+ "60117064444236841971802161585193689478337958649255415021805654859805036464"
+ "40548199239100050792877003355816639229553136239076508735759914822574862575"
+ "00742530207744771258955095793777842444242661733472762929938766870920560605"
+ "0270810842907692932019128194467627007";
final String p14_string = "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129"
+ "024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0"
+ "A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB"
+ "6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A"
+ "163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208"
+ "552BB9ED529077096966D670C354E4ABC9804F1746C08CA18217C32905E462E36C"
+ "E3BE39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF69558171"
+ "83995497CEA956AE515D2261898FA051015728E5A8AACAA68FFFFFFFFFFFFFFFF";
p1 = new BigInteger(p1_string);
p14 = new BigInteger(p14_string, 16);
g = new BigInteger("2");
}
public DhExchange()
{
}
public void init(int group, SecureRandom rnd)
{
k = null;
if (group == 1)
p = p1;
else if (group == 14)
p = p14;
else
throw new IllegalArgumentException("Unknown DH group " + group);
x = new BigInteger(p.bitLength() - 1, rnd);
e = g.modPow(x, p);
}
/**
* @return Returns the e.
* @throws IllegalStateException
*/
public BigInteger getE()
{
if (e == null)
throw new IllegalStateException("DhDsaExchange not initialized!");
return e;
}
/**
* @return Returns the shared secret k.
* @throws IllegalStateException
*/
public BigInteger getK()
{
if (k == null)
throw new IllegalStateException("Shared secret not yet known, need f first!");
return k;
}
/**
* @param f
*/
public void setF(BigInteger f)
{
if (e == null)
throw new IllegalStateException("DhDsaExchange not initialized!");
BigInteger zero = BigInteger.valueOf(0);
if (zero.compareTo(f) >= 0 || p.compareTo(f) <= 0)
throw new IllegalArgumentException("Invalid f specified!");
this.f = f;
this.k = f.modPow(x, p);
}
public byte[] calculateH(byte[] clientversion, byte[] serverversion, byte[] clientKexPayload,
byte[] serverKexPayload, byte[] hostKey)
{
HashForSSH2Types hash = new HashForSSH2Types("SHA1");
if (log.isEnabled())
{
log.log(90, "Client: '" + new String(clientversion) + "'");
log.log(90, "Server: '" + new String(serverversion) + "'");
}
hash.updateByteString(clientversion);
hash.updateByteString(serverversion);
hash.updateByteString(clientKexPayload);
hash.updateByteString(serverKexPayload);
hash.updateByteString(hostKey);
hash.updateBigInt(e);
hash.updateBigInt(f);
hash.updateBigInt(k);
return hash.getDigest();
}
}