diff --git a/cipher-ctr.c b/cipher-ctr.c
new file mode 100644
index 0000000..04975b4
--- /dev/null
+++ b/cipher-ctr.c
@@ -0,0 +1,146 @@
+/* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
+/*
+ * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include "includes.h"
+
+#include <sys/types.h>
+
+#include <stdarg.h>
+#include <string.h>
+
+#include <openssl/evp.h>
+
+#include "xmalloc.h"
+#include "log.h"
+
+/* compatibility with old or broken OpenSSL versions */
+#include "openbsd-compat/openssl-compat.h"
+
+#ifndef USE_BUILTIN_RIJNDAEL
+#include <openssl/aes.h>
+#endif
+
+const EVP_CIPHER *evp_aes_128_ctr(void);
+void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, size_t);
+
+struct ssh_aes_ctr_ctx
+{
+	AES_KEY		aes_ctx;
+	u_char		aes_counter[AES_BLOCK_SIZE];
+};
+
+/*
+ * increment counter 'ctr',
+ * the counter is of size 'len' bytes and stored in network-byte-order.
+ * (LSB at ctr[len-1], MSB at ctr[0])
+ */
+static void
+ssh_ctr_inc(u_char *ctr, size_t len)
+{
+	int i;
+
+	for (i = len - 1; i >= 0; i--)
+		if (++ctr[i])	/* continue on overflow */
+			return;
+}
+
+static int
+ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
+    LIBCRYPTO_EVP_INL_TYPE len)
+{
+	struct ssh_aes_ctr_ctx *c;
+	size_t n = 0;
+	u_char buf[AES_BLOCK_SIZE];
+
+	if (len == 0)
+		return (1);
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
+		return (0);
+
+	while ((len--) > 0) {
+		if (n == 0) {
+			AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
+			ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
+		}
+		*(dest++) = *(src++) ^ buf[n];
+		n = (n + 1) % AES_BLOCK_SIZE;
+	}
+	return (1);
+}
+
+static int
+ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
+    int enc)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
+		c = xmalloc(sizeof(*c));
+		EVP_CIPHER_CTX_set_app_data(ctx, c);
+	}
+	if (key != NULL)
+		AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
+		    &c->aes_ctx);
+	if (iv != NULL)
+		memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
+	return (1);
+}
+
+static int
+ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
+		memset(c, 0, sizeof(*c));
+		xfree(c);
+		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
+	}
+	return (1);
+}
+
+void
+ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, size_t len)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
+		fatal("ssh_aes_ctr_iv: no context");
+	if (doset)
+		memcpy(c->aes_counter, iv, len);
+	else
+		memcpy(iv, c->aes_counter, len);
+}
+
+const EVP_CIPHER *
+evp_aes_128_ctr(void)
+{
+	static EVP_CIPHER aes_ctr;
+
+	memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
+	aes_ctr.nid = NID_undef;
+	aes_ctr.block_size = AES_BLOCK_SIZE;
+	aes_ctr.iv_len = AES_BLOCK_SIZE;
+	aes_ctr.key_len = 16;
+	aes_ctr.init = ssh_aes_ctr_init;
+	aes_ctr.cleanup = ssh_aes_ctr_cleanup;
+	aes_ctr.do_cipher = ssh_aes_ctr;
+#ifndef SSH_OLD_EVP
+	aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
+	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
+#endif
+	return (&aes_ctr);
+}