--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ch/ethz/ssh2/crypto/dh/DhExchange.java	Fri Jul 18 11:21:46 2014 -0700
@@ -0,0 +1,196 @@
+/*
+ * Copyright (c) 2006-2013 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.ssh2.crypto.dh;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.SecureRandom;
+
+import ch.ethz.ssh2.crypto.digest.HashForSSH2Types;
+import ch.ethz.ssh2.log.Logger;
+import ch.ethz.ssh2.util.StringEncoder;
+
+/**
+ * @author Christian Plattner
+ * @version $Id: DhExchange.java 152 2014-04-28 11:02:23Z dkocher@sudo.ch $
+ */
+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 and private */
+
+    BigInteger f;
+    BigInteger y;
+
+	/* 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 clientInit(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);
+        }
+
+        while(true) {
+            x = new BigInteger(p.bitLength() - 1, rnd);
+            if(x.compareTo(BigInteger.ONE) > 0) {
+                break;
+            }
+        }
+
+        e = g.modPow(x, p);
+    }
+
+    public void serverInit(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);
+        }
+
+        y = new BigInteger(p.bitLength() - 1, rnd);
+
+        f = g.modPow(y, p);
+    }
+
+    /**
+     * @return Returns the e.
+     * @throws IllegalStateException
+     */
+    public BigInteger getE() {
+        if(e == null) {
+            throw new IllegalStateException("DhDsaExchange not initialized!");
+        }
+
+        return e;
+    }
+
+    /**
+     * @return Returns the f.
+     * @throws IllegalStateException
+     */
+    public BigInteger getF() {
+        if(f == null) {
+            throw new IllegalStateException("DhDsaExchange not initialized!");
+        }
+
+        return f;
+    }
+
+    /**
+     * @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!");
+        }
+
+        if(BigInteger.ZERO.compareTo(f) >= 0 || p.compareTo(f) <= 0) {
+            throw new IllegalArgumentException("Invalid f specified!");
+        }
+
+        this.f = f;
+        this.k = f.modPow(x, p);
+    }
+
+    /**
+     * @param e
+     */
+    public void setE(BigInteger e) {
+        if(f == null) {
+            throw new IllegalStateException("DhDsaExchange not initialized!");
+        }
+
+        if(BigInteger.ZERO.compareTo(e) >= 0 || p.compareTo(e) <= 0) {
+            throw new IllegalArgumentException("Invalid e specified!");
+        }
+
+        this.e = e;
+        this.k = e.modPow(y, p);
+    }
+
+    public byte[] calculateH(byte[] clientversion, byte[] serverversion, byte[] clientKexPayload,
+                             byte[] serverKexPayload, byte[] hostKey) throws IOException {
+        HashForSSH2Types hash = new HashForSSH2Types("SHA1");
+
+        if(log.isInfoEnabled()) {
+            log.info("Client: '" + StringEncoder.GetString(clientversion) + "'");
+            log.info("Server: '" + StringEncoder.GetString(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();
+    }
+}