From c85011ce5fd60cd4c941319b78cd567d14b2ec85 Mon Sep 17 00:00:00 2001
From: Nikos Mavrogiannopoulos <nmav@redhat.com>
Date: Sat, 20 Jan 2018 10:36:05 +0100
Subject: [PATCH 2/2] Added support for AES_SIV_CMAC_256 and AES_SIV_CMAC_512

This AEAD algorithm provides a way to make nonce-reuse a not critical
issue. That is particular useful to stateless servers that cannot ensure
that the nonce will not repeat. This cipher is used by
draft-ietf-ntp-using-nts-for-ntp-17.

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>
---
 Makefile.in                |   4 +-
 cmac-internal.h            |  54 ++++++
 cmac.c                     |  15 +-
 nettle-internal.h          |   2 +
 nettle.texinfo             |  94 +++++++++-
 siv-aes128-cmac.c          |  75 ++++++++
 siv-aes256-cmac.c          |  75 ++++++++
 siv-cmac.c                 | 196 +++++++++++++++++++++
 siv-cmac.h                 | 131 ++++++++++++++
 testsuite/.gitignore       |   2 +
 testsuite/.test-rules.make |   3 +
 testsuite/Makefile.in      |   2 +-
 testsuite/siv-test.c       | 350 +++++++++++++++++++++++++++++++++++++
 testsuite/testutils.h      |  13 ++
 14 files changed, 1005 insertions(+), 11 deletions(-)
 create mode 100644 cmac-internal.h
 create mode 100644 siv-aes128-cmac.c
 create mode 100644 siv-aes256-cmac.c
 create mode 100644 siv-cmac.c
 create mode 100644 siv-cmac.h
 create mode 100644 testsuite/siv-test.c

diff --git a/Makefile.in b/Makefile.in
index 440de9f7..90ee61d7 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -89,6 +89,7 @@ nettle_SOURCES = aes-decrypt-internal.c aes-decrypt.c \
 		 camellia256-meta.c \
 		 cast128.c cast128-meta.c cbc.c \
 		 ccm.c ccm-aes128.c ccm-aes192.c ccm-aes256.c cfb.c \
+		 siv-cmac.c siv-aes128-cmac.c siv-aes256-cmac.c \
 		 cnd-memcpy.c \
 		 chacha-crypt.c chacha-core-internal.c \
 		 chacha-poly1305.c chacha-poly1305-meta.c \
@@ -198,7 +199,8 @@ HEADERS = aes.h arcfour.h arctwo.h asn1.h blowfish.h \
 	  gcm.h gosthash94.h hmac.h \
 	  knuth-lfib.h hkdf.h \
 	  macros.h \
-	  cmac.h \
+	  cmac.h cmac-internal.h \
+	  siv-cmac.h siv-cmac-internal.h \
 	  md2.h md4.h \
 	  md5.h md5-compat.h \
 	  memops.h memxor.h \
diff --git a/cmac-internal.h b/cmac-internal.h
new file mode 100644
index 00000000..789588e6
--- /dev/null
+++ b/cmac-internal.h
@@ -0,0 +1,54 @@
+/* cmac.h
+
+   CMAC mode internal functions
+
+   Copyright (C) 2017 Red Hat, Inc.
+
+   Contributed by Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#ifndef NETTLE_CMAC_INTERNAL_H_INCLUDED
+#define NETTLE_CMAC_INTERNAL_H_INCLUDED
+
+#include "cmac.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define _cmac128_block_mulx _nettle_cmac128_block_mulx
+
+void _cmac128_block_mulx(union nettle_block16 *out,
+			 const union nettle_block16 *in);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CMAC_INTERNAL_H_INCLUDED */
diff --git a/cmac.c b/cmac.c
index 01fee79e..8be1cca4 100644
--- a/cmac.c
+++ b/cmac.c
@@ -44,13 +44,13 @@
 
 #include "memxor.h"
 #include "nettle-internal.h"
+#include "cmac-internal.h"
 #include "macros.h"
 
 /* shift one and XOR with 0x87. */
 #if WORDS_BIGENDIAN
-static void
-block_mulx(union nettle_block16 *dst,
-	   const union nettle_block16 *src)
+void _cmac128_block_mulx(union nettle_block16 *dst,
+			 const union nettle_block16 *src)
 {
   uint64_t carry = src->u64[0] >> 63;
   dst->u64[0] = (src->u64[0] << 1) | (src->u64[1] >> 63);
@@ -59,9 +59,8 @@ block_mulx(union nettle_block16 *dst,
 #else /* !WORDS_BIGENDIAN */
 #define LE_SHIFT(x) ((((x) & 0x7f7f7f7f7f7f7f7f) << 1) | \
                      (((x) & 0x8080808080808080) >> 15))
-static void
-block_mulx(union nettle_block16 *dst,
-	   const union nettle_block16 *src)
+void _cmac128_block_mulx(union nettle_block16 *dst,
+			 const union nettle_block16 *src)
 {
   uint64_t carry = (src->u64[0] & 0x80) >> 7;
   dst->u64[0] = LE_SHIFT(src->u64[0]) | ((src->u64[1] & 0x80) << 49);
@@ -83,8 +82,8 @@ cmac128_set_key(struct cmac128_ctx *ctx, const void *cipher,
   /* step 1 - generate subkeys k1 and k2 */
   encrypt(cipher, 16, L->b, const_zero.b);
 
-  block_mulx(&ctx->K1, L);
-  block_mulx(&ctx->K2, &ctx->K1);
+  _cmac128_block_mulx(&ctx->K1, L);
+  _cmac128_block_mulx(&ctx->K2, &ctx->K1);
 }
 
 #define MIN(x,y) ((x)<(y)?(x):(y))
diff --git a/nettle-internal.h b/nettle-internal.h
index dc379f1f..2937a710 100644
--- a/nettle-internal.h
+++ b/nettle-internal.h
@@ -78,6 +78,8 @@
 #define NETTLE_MAX_HASH_CONTEXT_SIZE (sizeof(struct sha3_224_ctx))
 #define NETTLE_MAX_SEXP_ASSOC 17
 #define NETTLE_MAX_CIPHER_BLOCK_SIZE 32
+/* maximum context size of 128-bit block ciphers */
+#define NETTLE_MAX_CIPHER16_CONTEXT_SIZE (sizeof(struct aes256_ctx))
 
 /* Doesn't quite fit with the other algorithms, because of the weak
  * keys. Weak keys are not reported, the functions will simply crash
diff --git a/nettle.texinfo b/nettle.texinfo
index 596c7098..f853f3e2 100644
--- a/nettle.texinfo
+++ b/nettle.texinfo
@@ -97,6 +97,7 @@ Cipher modes
 * CFB and CFB8::
 * GCM::                         
 * CCM::                         
+* SIV-CMAC::
 
 Keyed Hash Functions
 
@@ -2565,6 +2566,7 @@ more adventurous alternative, in particular if performance is important.
 * GCM::                         
 * CCM::                         
 * ChaCha-Poly1305::
+* SIV-CMAC::
 * nettle_aead abstraction::
 @end menu
 
@@ -3212,7 +3214,7 @@ These are identical to @code{ccm_encrypt_message} and @code{ccm_decrypt_message}
 except that @var{cipher} and @var{f} are replaced with a context structure.
 @end deftypefun
 
-@node ChaCha-Poly1305, nettle_aead abstraction, CCM, Authenticated encryption
+@node ChaCha-Poly1305, SIV-CMAC, CCM, Authenticated encryption
 @comment  node-name,  next,  previous,  up
 @subsection ChaCha-Poly1305
 
@@ -3295,6 +3297,96 @@ smaller than @code{CHACHA_POLY1305_DIGEST_SIZE}, only the first
 @var{length} octets of the digest are written.
 @end deftypefun
 
+@node SIV-CMAC, nettle_aead abstraction, ChaCha-Poly1305, Authenticated encryption
+@comment  node-name,  next,  previous,  up
+@subsection Counter with CBC-MAC mode
+
+@cindex SIV mode
+@cindex SIV-CMAC mode
+
+@acronym{SIV-CMAC} mode is a combination of counter mode with message
+authentication based on @acronym{CMAC}. Unlike other counter @acronym{AEAD}
+modes, it provides protection against accidental nonce misuse, making it
+a good choice for stateless-servers that cannot ensure nonce uniqueness.
+It is constructed on top of a block cipher which must have a block size of
+128 bits. Nettle's support for @acronym{SIV-CMAC} consists of
+a message encryption and authentication interface, for
+@acronym{SIV-CMAC} using AES as the underlying block cipher.
+When a nonce is re-used with this mode, message authenticity is retained
+however an attacker can determine whether the same plaintext was protected
+with the two messages sharing the nonce.
+These interfaces are defined in @file{<nettle/siv-cmac.h>}.
+
+Unlike other @acronym{AEAD} mode in @acronym{SIV-CMAC} the initialization
+vector serves as the tag. That means that in the generated ciphertext
+the tag precedes the ciphertext.
+
+Note also, that the @acronym{SIV-CMAC} algorithm introduces the notion
+of authenticated data which consist of multiple components. For example
+with @acronym{SIV-CMAC} the authentication tag of data @code{X} followed
+by @code{Y}, is different than the concatenated data @code{X || Y}. The interfaces
+described below follow the @acronym{AEAD} paradigm and do not allow access
+to this feature.
+
+@subsubsection General interface
+
+@defvr Constant SIV_BLOCK_SIZE
+@acronym{SIV-CMAC}'s block size, 16.
+@end defvr
+
+@defvr Constant SIV_DIGEST_SIZE
+Size of the @acronym{SIV-CMAC} digest or initialization vector, 16.
+@end defvr
+
+@defvr Constant SIV_MIN_NONCE_SIZE
+The the minimumsizes for an @acronym{SIV-CMAC} nonce, 0
+@end defvr
+
+@subsubsection @acronym{SIV-CMAC}-@acronym{AES} interface
+
+The @acronym{AES} @acronym{SIV-CMAC} functions provide an API for using
+@acronym{SIV-CMAC} mode with the @acronym{AES} block ciphers. The parameters
+all have the same meaning as the general and message interfaces, except
+that the @var{cipher}, @var{f}, and @var{ctx} parameters are replaced
+with an @acronym{AES} context structure, and a set-key function must be
+called before using any of the other functions in this interface.
+
+@deftp {Context struct} {struct siv_aes128_cmac_ctx}
+Holds state corresponding to a particular message encrypted using the
+AES-128 block cipher.
+@end deftp
+
+@deftp {Context struct} {struct siv_aes256_cmac_ctx}
+Holds state corresponding to a particular message encrypted using the
+AES-256 block cipher.
+@end deftp
+
+@deftypefun void siv_aes128_cmac_set_key (struct siv_aes128_cmac_ctx *@var{ctx}, const uint8_t *@var{key})
+@deftypefunx void siv_aes256_cmac_set_key (struct siv_aes256_cmac_ctx *@var{ctx}, const uint8_t *@var{key})
+Initializes the encryption key for the AES block cipher. One of these
+functions must be called before any of the other functions in the
+@acronym{AES} @acronym{SIV-CMAC} interface.
+@end deftypefun
+
+@deftypefun void siv_aes128_cmac_encrypt_message (struct siv_aes128_cmac_ctx *@var{ctx}, size_t @var{nlength}, const uint8_t *@var{nonce}, size_t @var{alength}, const uint8_t *@var{adata}, size_t @var{clength}, uint8_t *@var{dst}, const uint8_t *@var{src})
+@deftypefunx void siv_aes256_cmac_encrypt_message (struct siv_aes256_cmac_ctx *@var{ctx}, size_t @var{nlength}, const uint8_t *@var{nonce}, size_t @var{alength}, const uint8_t *@var{adata}, size_t @var{clength}, uint8_t *@var{dst}, const uint8_t *@var{src})
+Computes the message digest from the @var{adata} and @var{src}
+parameters, encrypts the plaintext from @var{src}, prepends the
+initialization vector to the ciphertext and outputs it to @var{dst}.
+The @var{clength} variable must be equal to the length of @var{src}
+plus @code{SIV_DIGEST_SIZE}.
+
+@end deftypefun
+
+@deftypefun int siv_aes128_cmac_decrypt_message (struct siv_aes128_cmac_ctx *@var{ctx}, size_t @var{nlength}, const uint8_t *@var{nonce}, size_t @var{alength}, const uint8_t *@var{adata}, size_t @var{mlength}, uint8_t *@var{dst}, const uint8_t *@var{src})
+@deftypefunx int siv_aes256_cmac_decrypt_message (struct siv_aes128_cmac_ctx *@var{ctx}, size_t @var{nlength}, const uint8_t *@var{nonce}, size_t @var{alength}, const uint8_t *@var{adata}, size_t @var{mlength}, uint8_t *@var{dst}, const uint8_t *@var{src})
+Decrypts the ciphertext from @var{src}, outputs the plaintext to
+@var{dst}, recalculates the initialization vector from @var{adata} and the
+plaintext. If the values of the received and calculated initialization vector
+are equal, this will return 1 indicating a valid and authenticated
+message. Otherwise, this function will return zero.
+@end deftypefun
+
 @node nettle_aead abstraction, , ChaCha-Poly1305, Authenticated encryption
 @comment  node-name,  next,  previous,  up
 @subsection The @code{struct nettle_aead} abstraction
diff --git a/siv-aes128-cmac.c b/siv-aes128-cmac.c
new file mode 100644
index 00000000..793279d1
--- /dev/null
+++ b/siv-aes128-cmac.c
@@ -0,0 +1,75 @@
+/* siv-aes128.c
+
+   AES-SIV, RFC5297
+
+   Copyright (C) 2017 Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "aes.h"
+#include "siv-cmac.h"
+#include "cmac.h"
+#include "ctr.h"
+#include "memxor.h"
+#include "memops.h"
+#include "cmac-internal.h"
+
+void
+siv_aes128_cmac_set_key(struct siv_aes128_cmac_ctx *ctx, const uint8_t *key)
+{
+  siv_cmac_set_key(&ctx->siv_cmac, &ctx->siv_cipher, &nettle_aes128, key);
+}
+
+void
+siv_aes128_cmac_encrypt_message(struct siv_aes128_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t clength, uint8_t *dst, const uint8_t *src)
+{
+  siv_cmac_encrypt_message(&ctx->siv_cmac, &nettle_aes128, &ctx->siv_cipher,
+			   nlength, nonce, alength, adata,
+			   clength, dst, src);
+}
+
+int
+siv_aes128_cmac_decrypt_message(struct siv_aes128_cmac_ctx *ctx,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t mlength, uint8_t *dst, const uint8_t *src)
+{
+  return siv_cmac_decrypt_message(&ctx->siv_cmac, &nettle_aes128, &ctx->siv_cipher,
+				  nlength, nonce, alength, adata,
+				  mlength, dst, src);
+}
diff --git a/siv-aes256-cmac.c b/siv-aes256-cmac.c
new file mode 100644
index 00000000..61cd1163
--- /dev/null
+++ b/siv-aes256-cmac.c
@@ -0,0 +1,75 @@
+/* siv-aes128.c
+
+   AES-SIV, RFC5297
+
+   Copyright (C) 2017 Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "aes.h"
+#include "siv-cmac.h"
+#include "cmac.h"
+#include "ctr.h"
+#include "memxor.h"
+#include "memops.h"
+#include "cmac-internal.h"
+
+void
+siv_aes256_cmac_set_key(struct siv_aes256_cmac_ctx *ctx, const uint8_t *key)
+{
+  siv_cmac_set_key(&ctx->siv_cmac, &ctx->siv_cipher, &nettle_aes256, key);
+}
+
+void
+siv_aes256_cmac_encrypt_message(struct siv_aes256_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t clength, uint8_t *dst, const uint8_t *src)
+{
+  siv_cmac_encrypt_message(&ctx->siv_cmac, &nettle_aes256, &ctx->siv_cipher,
+			   nlength, nonce, alength, adata,
+			   clength, dst, src);
+}
+
+int
+siv_aes256_cmac_decrypt_message(struct siv_aes256_cmac_ctx *ctx,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t mlength, uint8_t *dst, const uint8_t *src)
+{
+  return siv_cmac_decrypt_message(&ctx->siv_cmac, &nettle_aes256, &ctx->siv_cipher,
+				  nlength, nonce, alength, adata,
+				  mlength, dst, src);
+}
diff --git a/siv-cmac.c b/siv-cmac.c
new file mode 100644
index 00000000..94f65b0f
--- /dev/null
+++ b/siv-cmac.c
@@ -0,0 +1,196 @@
+/* siv-cmac.c
+
+   SIV-CMAC, RFC5297
+
+   Copyright (C) 2017 Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "aes.h"
+#include "siv-cmac.h"
+#include "cmac.h"
+#include "ctr.h"
+#include "memxor.h"
+#include "memops.h"
+#include "cmac-internal.h"
+#include "nettle-internal.h"
+
+/* This is only to allow the CMAC macros to expand in
+ * _siv_s2v */
+struct cmac128_syn {
+  struct cmac128_ctx ctx;
+  union {
+    uint64_t pad1[2]; /* to force a good alignment */
+    uint8_t pad[NETTLE_MAX_CIPHER16_CONTEXT_SIZE+16];
+  } cipher;
+};
+
+static
+void _siv_s2v(const struct nettle_cipher *nc,
+	      struct cmac128_syn *ctx,
+	      size_t alength, const uint8_t *adata,
+              size_t nlength, const uint8_t *nonce,
+              size_t plength, const uint8_t *pdata,
+              uint8_t *v)
+{
+  union nettle_block16 D, S, T;
+  static const union nettle_block16 const_one = { .b = {
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 }
+  };
+  static const union nettle_block16 const_zero = { .b = {
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
+  };
+
+  assert(nc->context_size <= NETTLE_MAX_CIPHER16_CONTEXT_SIZE);
+
+  if (nlength == 0 && alength == 0 && plength == 0) {
+    CMAC128_UPDATE(ctx, nc->encrypt, 16, const_one.b);
+    CMAC128_DIGEST(ctx, nc->encrypt, 16, v);
+    return;
+  }
+
+  CMAC128_UPDATE(ctx, nc->encrypt, 16, const_zero.b);
+  CMAC128_DIGEST(ctx, nc->encrypt, 16, D.b);
+
+  if (alength > 0) {
+    _cmac128_block_mulx(&D, &D);
+    CMAC128_UPDATE(ctx, nc->encrypt, alength, adata);
+    CMAC128_DIGEST(ctx, nc->encrypt, 16, S.b);
+
+    memxor(D.b, S.b, 16);
+  }
+
+  if (nlength > 0) {
+    _cmac128_block_mulx(&D, &D);
+    CMAC128_UPDATE(ctx, nc->encrypt, nlength, nonce);
+    CMAC128_DIGEST(ctx, nc->encrypt, 16, S.b);
+
+    memxor(D.b, S.b, 16);
+  }
+
+  /* Sn */
+  if (plength >= 16) {
+    CMAC128_UPDATE(ctx, nc->encrypt, plength-16, pdata);
+
+    pdata += plength-16;
+
+    memxor3(T.b, pdata, D.b, 16);
+  } else {
+    union nettle_block16 pad;
+
+    _cmac128_block_mulx(&T, &D);
+    memcpy(pad.b, pdata, plength);
+    pad.b[plength] = 0x80;
+    if (plength+1 < 16)
+      memset(&pad.b[plength+1], 0, 16-plength-1);
+
+    memxor(T.b, pad.b, 16);
+  }
+
+  CMAC128_UPDATE(ctx, nc->encrypt, 16, T.b);
+  CMAC128_DIGEST(ctx, nc->encrypt, 16, v);
+}
+
+void
+siv_cmac_set_key(void *_ctx, void *cipher,
+		 const struct nettle_cipher *nc,
+		 const uint8_t *key)
+{
+	/* We rely on the fact that the siv_cmac member of the context
+	 * is first in the context provided */
+	struct cmac128_syn *ctx = _ctx;
+
+	assert(nc->key_size <= SIV_MAX_KEY_SIZE/2);
+
+	CMAC128_SET_KEY(ctx, nc->set_encrypt_key, nc->encrypt, key);
+	nc->set_encrypt_key(cipher, key+nc->key_size);
+}
+
+void
+siv_cmac_encrypt_message(void *ctx,
+			 const struct nettle_cipher *nc,
+			 const void *cipher,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t clength, uint8_t *dst, const uint8_t *src)
+{
+	union nettle_block16 siv;
+	size_t slength;
+
+	assert(clength >= SIV_DIGEST_SIZE);
+	slength = clength - SIV_DIGEST_SIZE;
+
+	/* create CTR nonce */
+	_siv_s2v(nc,
+		 ctx, alength, adata,
+		 nlength, nonce, slength, src, siv.b);
+
+	memcpy(dst, siv.b, SIV_DIGEST_SIZE);
+	siv.b[8] &= ~0x80;
+	siv.b[12] &= ~0x80;
+
+	ctr_crypt(cipher, nc->encrypt, AES_BLOCK_SIZE, siv.b, slength, dst+SIV_DIGEST_SIZE, src);
+}
+
+int
+siv_cmac_decrypt_message(void *ctx,
+			 const struct nettle_cipher *nc,
+			 const void *cipher,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t mlength, uint8_t *dst, const uint8_t *src)
+{
+  union nettle_block16 siv;
+  union nettle_block16 ctr;
+
+  assert(mlength >= SIV_DIGEST_SIZE);
+
+  memcpy(ctr.b, src, SIV_DIGEST_SIZE);
+  ctr.b[8] &= ~0x80;
+  ctr.b[12] &= ~0x80;
+
+  ctr_crypt(cipher, nc->encrypt, AES_BLOCK_SIZE, ctr.b,
+            mlength-SIV_DIGEST_SIZE, dst, src+SIV_DIGEST_SIZE);
+
+  /* create CTR nonce */
+  _siv_s2v(nc,
+	   ctx, alength, adata,
+	   nlength, nonce, mlength-SIV_DIGEST_SIZE, dst, siv.b);
+
+  return memeql_sec(siv.b, src, SIV_DIGEST_SIZE);
+}
+
diff --git a/siv-cmac.h b/siv-cmac.h
new file mode 100644
index 00000000..ffbe4623
--- /dev/null
+++ b/siv-cmac.h
@@ -0,0 +1,131 @@
+/* siv.h
+
+   AES-SIV, RFC5297
+
+   Copyright (C) 2017 Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#ifndef NETTLE_SIV_H_INCLUDED
+#define NETTLE_SIV_H_INCLUDED
+
+#include "nettle-types.h"
+#include "nettle-meta.h"
+#include "cmac.h"
+#include "aes.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Name mangling */
+#define siv_cmac_set_key nettle_siv_cmac_set_key
+#define siv_cmac_encrypt_message nettle_siv_cmac_encrypt_message
+#define siv_cmac_decrypt_message nettle_siv_cmac_decrypt_message
+#define siv_aes128_cmac_set_key nettle_siv_aes128_cmac_set_key
+#define siv_aes128_cmac_encrypt_message nettle_siv_aes128_cmac_encrypt_message
+#define siv_aes128_cmac_decrypt_message nettle_siv_aes128_cmac_decrypt_message
+#define siv_aes256_cmac_set_key nettle_siv_aes256_cmac_set_key
+#define siv_aes256_cmac_encrypt_message nettle_siv_aes256_cmac_encrypt_message
+#define siv_aes256_cmac_decrypt_message nettle_siv_aes256_cmac_decrypt_message
+
+/* For SIV, the block size of the block cipher shall be 128 bits. */
+#define SIV_BLOCK_SIZE  16
+#define SIV_DIGEST_SIZE 16
+#define SIV_MIN_NONCE_SIZE 0
+#define SIV_MAX_KEY_SIZE (AES_MAX_KEY_SIZE*2)
+
+void
+siv_cmac_set_key(void *ctx, void *cipher,
+		 const struct nettle_cipher *nc,
+		 const uint8_t *key);
+
+void
+siv_cmac_encrypt_message(void *ctx,
+			 const struct nettle_cipher *nc,
+			 const void *cipher,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t clength, uint8_t *dst, const uint8_t *src);
+
+int
+siv_cmac_decrypt_message(void *ctx,
+			 const struct nettle_cipher *nc,
+			 const void *cipher,
+			 size_t nlength, const uint8_t *nonce,
+			 size_t alength, const uint8_t *adata,
+			 size_t mlength, uint8_t *dst, const uint8_t *src);
+
+/*
+ * SIV mode requires the aad and plaintext when building the IV, which
+ * prevents streaming processing and it incompatible with the AEAD API.
+ */
+
+#define SIV_CMAC_CTX(type) { struct CMAC128_CTX(type) siv_cmac; type siv_cipher; }
+
+/* AES_SIV_CMAC_256 */
+struct siv_aes128_cmac_ctx SIV_CMAC_CTX(struct aes128_ctx);
+
+void
+siv_aes128_cmac_set_key(struct siv_aes128_cmac_ctx *ctx, const uint8_t *key);
+
+void
+siv_aes128_cmac_encrypt_message(struct siv_aes128_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t clength, uint8_t *dst, const uint8_t *src);
+
+int
+siv_aes128_cmac_decrypt_message(struct siv_aes128_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t mlength, uint8_t *dst, const uint8_t *src);
+
+/* AES_SIV_CMAC_512 */
+struct siv_aes256_cmac_ctx SIV_CMAC_CTX(struct aes256_ctx);
+
+void
+siv_aes256_cmac_set_key(struct siv_aes256_cmac_ctx *ctx, const uint8_t *key);
+
+void
+siv_aes256_cmac_encrypt_message(struct siv_aes256_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t clength, uint8_t *dst, const uint8_t *src);
+
+int
+siv_aes256_cmac_decrypt_message(struct siv_aes256_cmac_ctx *ctx,
+				size_t nlength, const uint8_t *nonce,
+				size_t alength, const uint8_t *adata,
+				size_t mlength, uint8_t *dst, const uint8_t *src);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NETTLE_SIV_H_INCLUDED */
diff --git a/testsuite/.gitignore b/testsuite/.gitignore
index c3fc5c11..2a0d87ac 100644
--- a/testsuite/.gitignore
+++ b/testsuite/.gitignore
@@ -96,6 +96,8 @@
 /version-test
 /yarrow-test
 /xts-test
+/cmac-test
+/siv-test
 
 /test.in
 /test1.out
diff --git a/testsuite/.test-rules.make b/testsuite/.test-rules.make
index 6eee6e22..f827175e 100644
--- a/testsuite/.test-rules.make
+++ b/testsuite/.test-rules.make
@@ -136,6 +136,9 @@ ccm-test$(EXEEXT): ccm-test.$(OBJEXT)
 cmac-test$(EXEEXT): cmac-test.$(OBJEXT)
 	$(LINK) cmac-test.$(OBJEXT) $(TEST_OBJS) -o cmac-test$(EXEEXT)
 
+siv-test$(EXEEXT): siv-test.$(OBJEXT)
+	$(LINK) siv-test.$(OBJEXT) $(TEST_OBJS) -o siv-test$(EXEEXT)
+
 poly1305-test$(EXEEXT): poly1305-test.$(OBJEXT)
 	$(LINK) poly1305-test.$(OBJEXT) $(TEST_OBJS) -o poly1305-test$(EXEEXT)
 
diff --git a/testsuite/Makefile.in b/testsuite/Makefile.in
index 287c4f75..1bd42ffa 100644
--- a/testsuite/Makefile.in
+++ b/testsuite/Makefile.in
@@ -27,7 +27,7 @@ TS_NETTLE_SOURCES = aes-test.c arcfour-test.c arctwo-test.c \
 		    serpent-test.c twofish-test.c version-test.c \
 		    knuth-lfib-test.c \
 		    cbc-test.c cfb-test.c ctr-test.c gcm-test.c eax-test.c ccm-test.c \
-		    cmac-test.c \
+		    cmac-test.c siv-test.c \
 		    poly1305-test.c chacha-poly1305-test.c \
 		    hmac-test.c umac-test.c \
 		    meta-hash-test.c meta-cipher-test.c\
diff --git a/testsuite/siv-test.c b/testsuite/siv-test.c
new file mode 100644
index 00000000..39e87514
--- /dev/null
+++ b/testsuite/siv-test.c
@@ -0,0 +1,350 @@
+/* siv-test.c
+
+   Self-test and vectors for AES-SIV mode ciphers
+
+   Copyright (C) 2018 Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+/* The
+ * test vectors have been collected from the following standards:
+ *  RFC5297
+ */
+
+#include "testutils.h"
+#include "aes.h"
+#include "nettle-types.h"
+#include "siv-cmac.h"
+#include "knuth-lfib.h"
+
+static void
+test_compare_results(const char *name,
+        const struct tstring *adata,
+        /* Expected results. */
+        const struct tstring *e_clear,
+	const struct tstring *e_cipher,
+        /* Actual results. */
+        const void *clear,
+        const void *cipher,
+        const void *digest) /* digest optional. */
+{
+  if (digest && !MEMEQ(SIV_DIGEST_SIZE, e_cipher->data, digest))
+    {
+      fprintf(stderr, "%s digest failed:\nAdata:", name);
+      tstring_print_hex(adata);
+      fprintf(stderr, "\nInput: ");
+      tstring_print_hex(e_clear);
+      fprintf(stderr, "\nOutput: ");
+      print_hex(SIV_DIGEST_SIZE, digest);
+      fprintf(stderr, "\nExpected:");
+      print_hex(SIV_DIGEST_SIZE, e_cipher->data);
+      fprintf(stderr, "\n");
+      FAIL();
+    }
+  if (!MEMEQ(e_cipher->length, e_cipher->data, cipher))
+    {
+      fprintf(stderr, "%s: encryption failed\nAdata: ", name);
+      tstring_print_hex(adata);
+      fprintf(stderr, "\nInput: ");
+      tstring_print_hex(e_clear);
+      fprintf(stderr, "\nOutput: ");
+      print_hex(e_cipher->length, cipher);
+      fprintf(stderr, "\nExpected:");
+      tstring_print_hex(e_cipher);
+      fprintf(stderr, "\n");
+      FAIL();
+    }
+  if (!MEMEQ(e_clear->length, e_clear->data, clear))
+    {
+      fprintf(stderr, "%s decrypt failed:\nAdata:", name);
+      tstring_print_hex(adata);
+      fprintf(stderr, "\nInput: ");
+      tstring_print_hex(e_cipher);
+      fprintf(stderr, "\nOutput: ");
+      print_hex(e_clear->length, clear);
+      fprintf(stderr, "\nExpected:");
+      tstring_print_hex(e_clear);
+      fprintf(stderr, "\n");
+      FAIL();
+    }
+} /* test_compare_results */
+
+static void
+test_cipher_siv(const char *name,
+		nettle_set_key_func *siv_set_key,
+		nettle_encrypt_message_func *siv_encrypt,
+		nettle_decrypt_message_func *siv_decrypt,
+		unsigned context_size,
+		const struct nettle_cipher *cipher,
+		const struct tstring *key,
+		const struct tstring *nonce,
+		const struct tstring *authdata,
+		const struct tstring *cleartext,
+		const struct tstring *ciphertext)
+{
+  void *ctx = xalloc(context_size);
+  uint8_t *en_data;
+  uint8_t *de_data;
+  int ret;
+
+  ASSERT (key->length == cipher->key_size*2);
+  ASSERT (cleartext->length <= ciphertext->length);
+  ASSERT ((cleartext->length + SIV_BLOCK_SIZE) >= ciphertext->length);
+  ASSERT (ciphertext->length - cleartext->length == SIV_DIGEST_SIZE);
+
+  de_data = xalloc(cleartext->length+SIV_DIGEST_SIZE);
+  en_data = xalloc(ciphertext->length);
+  cipher->set_encrypt_key(ctx, key->data);
+
+  /* Ensure we get the same answers using the all-in-one API. */
+  memset(de_data, 0, cleartext->length);
+  memset(en_data, 0, ciphertext->length);
+
+  siv_set_key(ctx, key->data);
+  siv_encrypt(ctx, nonce->length, nonce->data,
+	      authdata->length, authdata->data,
+	      cleartext->length+SIV_DIGEST_SIZE, en_data, cleartext->data);
+
+  ret = siv_decrypt(ctx, nonce->length, nonce->data,
+				        authdata->length, authdata->data,
+				        ciphertext->length, de_data, ciphertext->data);
+
+  if (ret != 1) fprintf(stderr, "siv_decrypt_message failed to validate message\n");
+    test_compare_results(name, authdata,
+			 cleartext, ciphertext, de_data, en_data, NULL);
+
+  test_compare_results(name, authdata,
+		       cleartext, ciphertext, de_data, en_data, en_data);
+
+
+  /* Ensure that we can detect corrupted message or tag data. */
+  en_data[0] ^= 1;
+  ret = siv_decrypt(ctx, nonce->length, nonce->data,
+	            authdata->length, authdata->data,
+		    ciphertext->length, de_data, en_data);
+  if (ret != 0) fprintf(stderr, "siv_decrypt_message failed to detect corrupted message\n");
+
+  /* Ensure we can detect corrupted adata. */
+  if (authdata->length) {
+    en_data[0] ^= 1;
+    ret = siv_decrypt(ctx, nonce->length, nonce->data,
+		      authdata->length-1, authdata->data,
+		      ciphertext->length, de_data, en_data);
+    if (ret != 0) fprintf(stderr, "siv_decrypt_message failed to detect corrupted message\n");
+  }
+
+
+  free(ctx);
+  free(en_data);
+  free(de_data);
+}
+
+#define test_siv_aes128(name, ctx_size, cipher, key, nonce, authdata, cleartext, ciphertext) \
+	test_cipher_siv(name, (nettle_set_key_func*)siv_aes128_cmac_set_key, \
+			(nettle_encrypt_message_func*)siv_aes128_cmac_encrypt_message, \
+			(nettle_decrypt_message_func*)siv_aes128_cmac_decrypt_message, ctx_size, cipher, \
+			key, nonce, authdata, cleartext, ciphertext)
+
+#define test_siv_aes256(name, ctx_size, cipher, key, nonce, authdata, cleartext, ciphertext) \
+	test_cipher_siv(name, (nettle_set_key_func*)siv_aes256_cmac_set_key, \
+			(nettle_encrypt_message_func*)siv_aes256_cmac_encrypt_message, \
+			(nettle_decrypt_message_func*)siv_aes256_cmac_decrypt_message, ctx_size, cipher, \
+			key, nonce, authdata, cleartext, ciphertext)
+
+void
+test_main(void)
+{
+  /*
+   * Example with no nonce, no AD and no plaintext; taken from
+   * https://github.com/miscreant/miscreant/blob/master/vectors/aes_siv.tjson
+   * however we don't interoperate.
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+		  &nettle_aes128,
+		  SHEX("fffefdfc fbfaf9f8 f7f6f5f4 f3f2f1f0"
+		       "f0f1f2f3 f4f5f6f7 f8f9fafb fcfdfeff"),
+		  SHEX(""),
+		  SHEX(""),
+		  SHEX(""),
+		  SHEX("949f99cb cc3eb5da6 d3c45d0 f59aa9c7"));
+
+  /*
+   * Example with no nonce, no AD and plaintext; taken from
+   * https://github.com/miscreant/miscreant/blob/master/vectors/aes_siv.tjson
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+		  &nettle_aes128,
+		  SHEX("fffefdfc fbfaf9f8 f7f6f5f4 f3f2f1f0"
+		       "f0f1f2f3 f4f5f6f7 f8f9fafb fcfdfeff"),
+		  SHEX(""),
+		  SHEX(""),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"),
+		  SHEX("f304f912 863e303d 5b540e50 57c7010c"
+		       "942ffaf4 5b0e5ca5 fb9a56a5 263bb065"));
+
+  /*
+   * Example without nonce length < 16 (RFC5297)
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+		  &nettle_aes128,
+		  SHEX("fffefdfc fbfaf9f8 f7f6f5f4 f3f2f1f0"
+		       "f0f1f2f3 f4f5f6f7 f8f9fafb fcfdfeff"),
+		  SHEX(""),
+		  SHEX("10111213 14151617 18191a1b 1c1d1e1f"
+		       "20212223 24252627"),
+		  SHEX("11223344 55667788 99aabbcc ddee"),
+		  SHEX("85632d07 c6e8f37f 950acd32 0a2ecc93"
+		       "40c02b96 90c4dc04 daef7f6a fe5c"));
+
+  /*
+   * Example without nonce length > 16
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+		  &nettle_aes128,
+		  SHEX("7f7e7d7c 7b7a7978 77767574 73727170"
+		       "40414243 44454647 48494a4b 4c4d4e4f"),
+		  SHEX(""),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"
+		       "deaddada deaddada ffeeddcc bbaa9988"
+		       "77665544 33221100"),
+		  SHEX("74686973 20697320 736f6d65 20706c61"
+		       "696e7465 78742074 6f20656e 63727970"
+		       "74207573 696e6720 5349562d 414553"),
+		  SHEX("c12ccaa7 54e1b3fa 4f416c18 415625ca"
+		       "472fbee de5bc03f 34934819 a9abb20b5"
+		       "8cd019c 470ac832 f6eb9ddf 0656c5dce"
+		       "ffe611a 5a5ca3e1 c3c12da5 6e4bb87"));
+
+  /*
+   * Example with single AAD, length > 16
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+	          &nettle_aes128,
+		  SHEX("7f7e7d7c 7b7a7978 77767574 73727170"
+		       "40414243 44454647 48494a4b 4c4d4e4f"),
+		  SHEX("09f91102 9d74e35b d84156c5 635688c0"),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"
+		       "deaddada deaddada ffeeddcc bbaa9988"
+		       "77665544 33221100"),
+		  SHEX("74686973 20697320 736f6d65 20706c61"
+		       "696e7465 78742074 6f20656e 63727970"
+		       "74207573 696e6720 5349562d 414553"),
+		  SHEX("85825e22 e90cf2dd da2c548d c7c1b631"
+		       "0dcdaca0 cebf9dc6 cb90583f 5bf1506e"
+		       "02cd4883 2b00e4e5 98b2b22a 53e6199d"
+		       "4df0c166 6a35a043 3b250dc1 34d776"));
+
+  /*
+   * Example with single AAD, length < 16
+   */
+  test_siv_aes128("AES_SIV_CMAC256", sizeof(struct siv_aes128_cmac_ctx),
+	          &nettle_aes128,
+		  SHEX("7f7e7d7c 7b7a7978 77767574 73727170"
+		       "40414243 44454647 48494a4b 4c4d4e4f"),
+		  SHEX("09f91102 9d74e35b d84156c5 635688c0"),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"
+		       "deaddada deaddada ffeeddcc bbaa9988"
+		       "77665544 33221100"),
+		  SHEX("11223344 55667788 99aabbcc ddee"),
+		  SHEX("15f83882 14bdc94e 3ec4c7c3 69863746"
+		       "cd72d317 4b20a1e4 a0894fb7 cd78"));
+
+
+  /* AES-SIV-CMAC-512 (AES-256) from dchest/siv repo
+   */
+  test_siv_aes256("AES_SIV_CMAC512", sizeof(struct siv_aes256_cmac_ctx),
+		  &nettle_aes256,
+		  SHEX("fffefdfc fbfaf9f8 f7f6f5f4 f3f2f1f0"
+		       "6f6e6d6c 6b6a6968 67666564 63626160"
+		       "f0f1f2f3 f4f5f6f7 f8f9fafb fcfdfeff"
+		       "00010203 04050607 08090a0b 0c0d0e0f"),
+		  SHEX(""),
+		  SHEX("10111213 14151617 18191a1b 1c1d1e1f"
+		       "20212223 24252627"),
+		  SHEX("11223344 55667788 99aabbcc ddee"),
+		  SHEX("f125274c 598065cf c26b0e71 57502908"
+		       "8b035217 e380cac8 919ee800 c126"));
+
+
+  /* AES-SIV-CMAC-512 (AES-256)
+   */
+  test_siv_aes256("AES_SIV_CMAC512", sizeof(struct siv_aes256_cmac_ctx),
+		  &nettle_aes256,
+		  SHEX("c27df2fd aec35d4a 2a412a50 c3e8c47d"
+		       "2d568e91 a38e5414 8abdc0b6 e86caf87"
+		       "695c0a8a df4c5f8e b2c6c8b1 36529864"
+		       "f3b84b3a e8e3676c e760c461 f3a13e83"),
+		  SHEX(""),
+		  SHEX("10111213 14151617 18191a1b 1c1d1e1f"
+		       "20212223 24252627"),
+		  SHEX("11223344 55667788 99aabbcc ddee"),
+		  SHEX("ae2b1bd1 ba7fcd6a 4f9f7eb2 4b40f766"
+		       "86053ffd c384cb19 76031f46 3013"));
+
+  /*
+   * Example without nonce length > 16
+   */
+  test_siv_aes256("AES_SIV_CMAC512", sizeof(struct siv_aes256_cmac_ctx),
+		  &nettle_aes256,
+		  SHEX("c27df2fd aec35d4a 2a412a50 c3e8c47d"
+		       "2d568e91 a38e5414 8abdc0b6 e86caf87"
+		       "695c0a8a df4c5f8e b2c6c8b1 36529864"
+		       "f3b84b3a e8e3676c e760c461 f3a13e83"),
+		  SHEX(""),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"
+		       "deaddada deaddada ffeeddcc bbaa9988"
+		       "77665544 33221100"),
+		  SHEX("74686973 20697320 736f6d65 20706c61"
+		       "696e7465 78742074 6f20656e 63727970"
+		       "74207573 696e6720 5349562d 414553"),
+		  SHEX("79476aaa 388374fe 97d0db51 596cb5ee"
+		       "a933e001 412026c7 956c82dd b753b1af"
+		       "3d7d49ac 474a800a c14b4bab a4542067"
+		       "83647ef9 51315dab b7a2c05b 288ba8"));
+
+  /*
+   * Example with single AAD, length > 16
+   */
+  test_siv_aes256("AES_SIV_CMAC512", sizeof(struct siv_aes256_cmac_ctx),
+	          &nettle_aes256,
+		  SHEX("c27df2fd aec35d4a 2a412a50 c3e8c47d"
+		       "2d568e91 a38e5414 8abdc0b6 e86caf87"
+		       "695c0a8a df4c5f8e b2c6c8b1 36529864"
+		       "f3b84b3a e8e3676c e760c461 f3a13e83"),
+		  SHEX("09f91102 9d74e35b d84156c5 635688c0"),
+		  SHEX("00112233 44556677 8899aabb ccddeeff"
+		       "deaddada deaddada ffeeddcc bbaa9988"
+		       "77665544 33221100"),
+		  SHEX("74686973 20697320 736f6d65 20706c61"
+		       "696e7465 78742074 6f20656e 63727970"
+		       "74207573 696e6720 5349562d 414553"),
+		  SHEX("5a979b0d a58fde80 51621ae6 bf96feda"
+		       "50933da8 047bc306 fabaf0c3 d9fa8471"
+		       "c70a7def 39a2f91d 68a2021c 99ac7e2a"
+		       "24535a13 4ba23ec1 5787cebe 5c53cc"));
+}
diff --git a/testsuite/testutils.h b/testsuite/testutils.h
index ded57db6..3a1872f1 100644
--- a/testsuite/testutils.h
+++ b/testsuite/testutils.h
@@ -176,6 +176,19 @@ test_armor(const struct nettle_armor *armor,
            const uint8_t *data,
            const char *ascii);
 
+/* AEAD ciphers */
+typedef void
+nettle_encrypt_message_func(void *ctx,
+			    size_t nlength, const uint8_t *nonce,
+			    size_t alength, const uint8_t *adata,
+			    size_t clength, uint8_t *dst, const uint8_t *src);
+
+typedef int
+nettle_decrypt_message_func(void *ctx,
+			    size_t nlength, const uint8_t *nonce,
+			    size_t alength, const uint8_t *adata,
+			    size_t mlength, uint8_t *dst, const uint8_t *src);
+
 #if WITH_HOGWEED
 
 #if NETTLE_USE_MINI_GMP
-- 
2.20.1

