--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/trilead/ssh2/DHGexParameters.java	Thu May 22 10:41:19 2014 -0700
@@ -0,0 +1,114 @@
+
+package com.trilead.ssh2;
+
+/**
+ * A <code>DHGexParameters</code> object can be used to specify parameters for
+ * the diffie-hellman group exchange.
+ * <p>
+ * Depending on which constructor is used, either the use of a
+ * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> or <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code>
+ * can be forced.
+ *
+ * @see Connection#setDHGexParameters(DHGexParameters)
+ * @author Christian Plattner, plattner@trilead.com
+ * @version $Id: DHGexParameters.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $
+ */
+
+public class DHGexParameters {
+    private final int min_group_len;
+    private final int pref_group_len;
+    private final int max_group_len;
+
+    private static final int MIN_ALLOWED = 1024;
+    private static final int MAX_ALLOWED = 8192;
+
+    /**
+     * Same as calling {@link #DHGexParameters(int, int, int) DHGexParameters(1024, 1024, 4096)}.
+     * This is also the default used by the Connection class.
+     *
+     */
+    public DHGexParameters() {
+        this(1024, 1024, 4096);
+    }
+
+    /**
+     * This constructor can be used to force the sending of a
+     * <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code> request.
+     * Internally, the minimum and maximum group lengths will
+     * be set to zero.
+     *
+     * @param pref_group_len has to be &gt= 1024 and &lt;= 8192
+     */
+    public DHGexParameters(int pref_group_len) {
+        if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED))
+            throw new IllegalArgumentException("pref_group_len out of range!");
+
+        this.pref_group_len = pref_group_len;
+        this.min_group_len = 0;
+        this.max_group_len = 0;
+    }
+
+    /**
+     * This constructor can be used to force the sending of a
+     * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> request.
+     * <p>
+     * Note: older OpenSSH servers don't understand this request, in which
+     * case you should use the {@link #DHGexParameters(int)} constructor.
+     * <p>
+     * All values have to be &gt= 1024 and &lt;= 8192. Furthermore,
+     * min_group_len &lt;= pref_group_len &lt;= max_group_len.
+     *
+     * @param min_group_len
+     * @param pref_group_len
+     * @param max_group_len
+     */
+    public DHGexParameters(int min_group_len, int pref_group_len, int max_group_len) {
+        if ((min_group_len < MIN_ALLOWED) || (min_group_len > MAX_ALLOWED))
+            throw new IllegalArgumentException("min_group_len out of range!");
+
+        if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED))
+            throw new IllegalArgumentException("pref_group_len out of range!");
+
+        if ((max_group_len < MIN_ALLOWED) || (max_group_len > MAX_ALLOWED))
+            throw new IllegalArgumentException("max_group_len out of range!");
+
+        if ((pref_group_len < min_group_len) || (pref_group_len > max_group_len))
+            throw new IllegalArgumentException("pref_group_len is incompatible with min and max!");
+
+        if (max_group_len < min_group_len)
+            throw new IllegalArgumentException("max_group_len must not be smaller than min_group_len!");
+
+        this.min_group_len = min_group_len;
+        this.pref_group_len = pref_group_len;
+        this.max_group_len = max_group_len;
+    }
+
+    /**
+     * Get the maximum group length.
+     *
+     * @return the maximum group length, may be <code>zero</code> if
+     *         SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested
+     */
+    public int getMax_group_len() {
+        return max_group_len;
+    }
+
+    /**
+     * Get the minimum group length.
+     *
+     * @return minimum group length, may be <code>zero</code> if
+     *         SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested
+     */
+    public int getMin_group_len() {
+        return min_group_len;
+    }
+
+    /**
+     * Get the preferred group length.
+     *
+     * @return the preferred group length
+     */
+    public int getPref_group_len() {
+        return pref_group_len;
+    }
+}