--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ch/ethz/ssh2/DHGexParameters.java	Fri Jul 18 11:21:46 2014 -0700
@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.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
+ * @version 2.50, 03/15/10
+ */
+
+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;
+	}
+}