Index: ssharcf.c
===================================================================
--- ssharcf.c	(revision 0)
+++ ssharcf.c	(revision 0)
@@ -0,0 +1,125 @@
+/*
+ * Arcfour (RC4) implementation for PuTTY.
+ *
+ * Coded from Schneier.
+ */
+
+#include <assert.h>
+#include "ssh.h"
+
+typedef struct {
+    unsigned char i, j, s[256];
+} ArcfourContext;
+
+static void arcfour_block(void *handle, unsigned char *blk, int len)
+{
+    ArcfourContext *ctx = (ArcfourContext *)handle;
+    unsigned k;
+    unsigned char tmp, i, j, *s;
+
+    s = ctx->s;
+    i = ctx->i; j = ctx->j;
+    for (k = 0; k < len; k++) {
+	i  = (i + 1) & 0xff;
+	j  = (j + s[i]) & 0xff;
+	tmp = s[i]; s[i] = s[j]; s[j] = tmp;
+	blk[k] ^= s[(s[i]+s[j]) & 0xff];
+    }
+    ctx->i = i; ctx->j = j;
+}
+
+static void arcfour_setkey(ArcfourContext *ctx, unsigned char const *key,
+			   unsigned keybytes)
+{
+    unsigned char tmp, k[256], *s;
+    unsigned i, j;
+
+    s = ctx->s;
+    assert(keybytes <= 256);
+    ctx->i = ctx->j = 0;
+    for (i = 0; i < 256; i++) {
+	s[i] = i;
+	k[i] = key[i % keybytes];
+    }
+    j = 0;
+    for (i = 0; i < 256; i++) {
+	j = (j + s[i] + k[i]) & 0xff;
+	tmp = s[i]; s[i] = s[j]; s[j] = tmp;
+    }
+}
+
+/* -- Interface with PuTTY -- */
+
+static void *arcfour_make_context(void)
+{
+    return snew(ArcfourContext);
+}
+
+static void arcfour_free_context(void *handle)
+{
+    sfree(handle);
+}
+
+static void arcfour_key(void *handle, unsigned char *key)
+{
+    ArcfourContext *ctx = (ArcfourContext *)handle;
+    arcfour_setkey(ctx, key, 16);
+}
+
+static void arcfour_stir(ArcfourContext *ctx)
+{
+    unsigned char *junk = snewn(1536, unsigned char);
+    memset(junk, 0, 1536);
+    arcfour_block(ctx, junk, 1536);
+}
+
+static void arcfour128_key(void *handle, unsigned char *key)
+{
+    ArcfourContext *ctx = (ArcfourContext *)handle;
+    arcfour_setkey(ctx, key, 16);
+    arcfour_stir(ctx);
+}
+
+static void arcfour256_key(void *handle, unsigned char *key)
+{
+    ArcfourContext *ctx = (ArcfourContext *)handle;
+    arcfour_setkey(ctx, key, 32);
+    arcfour_stir(ctx);
+}
+
+static void arcfour_iv(void *handle, unsigned char *key)
+{
+
+}
+
+const struct ssh2_cipher ssh_arcfour_ssh2 = {
+    arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour_key,
+    arcfour_block, arcfour_block,
+    "arcfour",
+    1, 128, "Arcfour"
+};
+
+const struct ssh2_cipher ssh_arcfour128_ssh2 = {
+    arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour128_key,
+    arcfour_block, arcfour_block,
+    "arcfour128-draft-00@putty.projects.tartarus.org",
+    1, 128, "Arcfour"
+};
+
+const struct ssh2_cipher ssh_arcfour256_ssh2 = {
+    arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour256_key,
+    arcfour_block, arcfour_block,
+    "arcfour256-draft-00@putty.projects.tartarus.org",
+    1, 256, "Arcfour"
+};
+
+static const struct ssh2_cipher *const arcfour_list[] = {
+    &ssh_arcfour256_ssh2,
+    &ssh_arcfour128_ssh2,
+    &ssh_arcfour_ssh2
+};
+
+const struct ssh2_ciphers ssh2_arcfour = {
+    sizeof(arcfour_list) / sizeof(*arcfour_list),
+    arcfour_list
+};
Index: config.c
===================================================================
--- config.c	(revision 5584)
+++ config.c	(working copy)
@@ -120,6 +120,7 @@
 	    { "Blowfish",		CIPHER_BLOWFISH },
 	    { "DES",			CIPHER_DES },
 	    { "AES (SSH-2 only)",	CIPHER_AES },
+	    { "Arcfour (SSH-2 only)",	CIPHER_ARCFOUR },
 	    { "-- warn below here --",	CIPHER_WARN }
 	};
 
Index: settings.c
===================================================================
--- settings.c	(revision 5584)
+++ settings.c	(working copy)
@@ -17,6 +17,7 @@
     { "aes",	    CIPHER_AES },
     { "blowfish",   CIPHER_BLOWFISH },
     { "3des",	    CIPHER_3DES },
     { "WARN",	    CIPHER_WARN },
+    { "arcfour",    CIPHER_ARCFOUR },
     { "des",	    CIPHER_DES }
 };
Index: ssh.c
===================================================================
--- ssh.c	(revision 5584)
+++ ssh.c	(working copy)
@@ -4927,6 +4927,9 @@
 	      case CIPHER_AES:
 		s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_aes;
 		break;
+	      case CIPHER_ARCFOUR:
+		s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_arcfour;
+		break;
 	      case CIPHER_WARN:
 		/* Flag for later. Don't bother if it's the last in
 		 * the list. */
Index: ssh.h
===================================================================
--- ssh.h	(revision 5584)
+++ ssh.h	(working copy)
@@ -233,6 +233,7 @@
 extern const struct ssh2_ciphers ssh2_des;
 extern const struct ssh2_ciphers ssh2_aes;
 extern const struct ssh2_ciphers ssh2_blowfish;
+extern const struct ssh2_ciphers ssh2_arcfour;
 extern const struct ssh_kex ssh_diffiehellman_group1;
 extern const struct ssh_kex ssh_diffiehellman_group14;
 extern const struct ssh_kex ssh_diffiehellman_gex;
Index: putty.h
===================================================================
--- putty.h	(revision 5584)
+++ putty.h	(working copy)
@@ -261,6 +261,7 @@
     CIPHER_BLOWFISH,
     CIPHER_AES,			       /* (SSH-2 only) */
     CIPHER_DES,
+    CIPHER_ARCFOUR,
     CIPHER_MAX			       /* no. ciphers (inc warn) */
 };
 
Index: Recipe
===================================================================
--- Recipe	(revision 5584)
+++ Recipe	(working copy)
@@ -205,7 +205,7 @@
 # SSH back end (putty, plink, pscp, psftp).
 SSH      = ssh sshcrc sshdes sshmd5 sshrsa sshrand sshsha sshblowf
          + sshdh sshcrcda sshpubk sshzlib sshdss x11fwd portfwd
-         + sshaes sshsh512 sshbn wildcard pinger
+         + sshaes sshsh512 sshbn wildcard pinger ssharcf
 WINSSH   = SSH winnoise winpgntc
 UXSSH    = SSH uxnoise uxagentc
 MACSSH   = SSH macnoise