diff --git a/.github/test.sh b/.github/test.sh
index af67c7b..25e96bc 100755
--- a/.github/test.sh
+++ b/.github/test.sh
@@ -22,6 +22,6 @@ run_task() {
   echo '::endgroup::'
 }
 
-for item in aes cbcdes cbcmac_des cbctdes ctraes des tdes; do
+for item in aes cbcaes cbcdes cbcmac_des cbctdes ctraes des tdes; do
   run_task "$item" "$1"
 done
diff --git a/README.md b/README.md
index d97f87d..1deaf0b 100644
--- a/README.md
+++ b/README.md
@@ -8,9 +8,7 @@ They serve as proof of concept, for example how to implement a pipeline using
 only (local) variables instead of (global) signals. Furthermore they were used
 how to do a VHDL-to-Verilog conversion for learning purposes.
 
-The testbenches to verify [DES](des/sim/vhdl/), [AES](aes/sim/vhdl/) and [CTR-AES](ctraes/sim/vhdl/) are examples
-how useful GHDLs VHPIdirect is. They use openSSL as reference models to check the correctness
-of the VHDL implementation.
+The testbenches to verify [DES](des/sim/vhdl/), [AES](aes/sim/vhdl/), [CTR-AES](ctraes/sim/vhdl/) and [CBC-AES](cbcaes/sim/vhdl/) are examples how useful GHDLs VHPIdirect is. They use openSSL as reference models to check the correctness of the VHDL implementation.
 
 *HINT:*
 
diff --git a/cbcaes/sim/vhdl/Makefile b/cbcaes/sim/vhdl/Makefile
new file mode 100644
index 0000000..87ca198
--- /dev/null
+++ b/cbcaes/sim/vhdl/Makefile
@@ -0,0 +1,99 @@
+# ======================================================================
+# AES CBC encryption/decryption
+# Copyright (C) 2021 Torsten Meissner
+#-----------------------------------------------------------------------
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of 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.
+
+# This program 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 a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+# ======================================================================
+
+
+.SECONDARY:
+
+
+DESIGN_NAME := cbcaes
+RTL_SRC := \
+  ../../../aes/rtl/vhdl/aes_pkg.vhd \
+  ../../../aes/rtl/vhdl/aes_enc.vhd \
+  ../../../aes/rtl/vhdl/aes_dec.vhd \
+  ../../../aes/rtl/vhdl/aes.vhd \
+  ../../rtl/vhdl/$(DESIGN_NAME).vhd
+
+
+SIM_SRC   := tb_$(DESIGN_NAME).vhd
+C_SRC     := tb_$(DESIGN_NAME).c
+
+
+OSVVM_DIR := ../../../lib/osvvm
+OSVVM_SRC := \
+  $(OSVVM_DIR)/NamePkg.vhd  \
+  $(OSVVM_DIR)/OsvvmGlobalPkg.vhd  \
+  $(OSVVM_DIR)/VendorCovApiPkg.vhd  \
+  $(OSVVM_DIR)/TranscriptPkg.vhd  \
+  $(OSVVM_DIR)/TextUtilPkg.vhd  \
+  $(OSVVM_DIR)/AlertLogPkg.vhd  \
+  $(OSVVM_DIR)/MessagePkg.vhd  \
+  $(OSVVM_DIR)/SortListPkg_int.vhd  \
+  $(OSVVM_DIR)/RandomBasePkg.vhd  \
+  $(OSVVM_DIR)/RandomPkg.vhd  \
+  $(OSVVM_DIR)/CoveragePkg.vhd  \
+  $(OSVVM_DIR)/MemoryPkg.vhd  \
+  $(OSVVM_DIR)/ScoreboardGenericPkg.vhd  \
+  $(OSVVM_DIR)/ScoreboardPkg_slv.vhd  \
+  $(OSVVM_DIR)/ScoreboardPkg_int.vhd  \
+  $(OSVVM_DIR)/ResolutionPkg.vhd  \
+  $(OSVVM_DIR)/TbUtilPkg.vhd  \
+  $(OSVVM_DIR)/OsvvmContext.vhd
+
+VHD_STD := 08
+
+
+.PHONY: sim
+sim: tb_$(DESIGN_NAME).ghw
+
+
+.PHONY: compile
+compile: tb_$(DESIGN_NAME)
+
+
+osvvm work:
+	mkdir $@
+
+
+osvvm/OsvvmContext.o: $(OSVVM_SRC) | osvvm
+	@echo "Analyze OSVVM library ..."
+	ghdl -a --std=$(VHD_STD) -Wno-hide --work=osvvm --workdir=osvvm $(OSVVM_SRC)
+
+
+tb_$(DESIGN_NAME): ${RTL_SRC} ${SIM_SRC} ${C_SRC} osvvm/OsvvmContext.o | work
+	@echo "Analyze testbench & design ..."
+	ghdl -a --std=$(VHD_STD) -fpsl --workdir=work -P=osvvm ${RTL_SRC} ${SIM_SRC}
+	@echo "Elaborate testbench & design ..."
+	ghdl -e --std=$(VHD_STD) -fpsl --workdir=work -P=osvvm -Wl,$@.c -Wl,-lcrypto -Wl,-lssl $@
+
+
+tb_$(DESIGN_NAME).ghw: tb_$(DESIGN_NAME)
+	@echo "Run testbench ..."
+	ghdl -r $(basename $@) --wave=$@ --assert-level=error --psl-report=$(basename $@)_psl_report.json
+
+
+.PHONY: wave
+wave: tb_$(DESIGN_NAME).ghw
+	@echo "Run GTKwave ..."
+	gtkwave -S tb_$(DESIGN_NAME).tcl tb_$(DESIGN_NAME).ghw
+
+
+.PHONY: clean
+clean:
+	@echo "Cleaning simulation files ..."
+	rm -rf tb_$(DESIGN_NAME) tb_$(DESIGN_NAME).ghw *.o *.json work/ osvvm/
diff --git a/cbcaes/sim/vhdl/tb_cbcaes.c b/cbcaes/sim/vhdl/tb_cbcaes.c
new file mode 100644
index 0000000..b2b88bb
--- /dev/null
+++ b/cbcaes/sim/vhdl/tb_cbcaes.c
@@ -0,0 +1,182 @@
+#include <stdio.h>
+#include <string.h>
+#include <openssl/conf.h>
+#include <openssl/evp.h>
+#include <openssl/err.h>
+
+static const char HDL_LOGIC_CHAR[] = { 'U', 'X', '0', '1', 'Z', 'W', 'L', 'H', '-'};
+
+enum HDL_LOGIC_STATES {
+HDL_U = 0,
+HDL_X = 1,
+HDL_0 = 2,
+HDL_1 = 3,
+HDL_Z = 4,
+HDL_W = 5,
+HDL_L = 6,
+HDL_H = 7,
+HDL_D = 8,
+};
+
+EVP_CIPHER_CTX *ctx;
+
+void slv_to_uchar(char* datain, unsigned char* dataout, int bytelen) {
+
+  for (int i = 0; i < bytelen; i++) {
+    for (int y = 0; y < 8; y++) {
+      if (*datain == HDL_1) {
+        *dataout |= 1 << y;
+      } else if (*datain == HDL_0) {
+        *dataout &= ~(1 << y);
+      }
+      datain++;
+    }
+    dataout++;
+  }
+
+  return;
+
+}
+
+
+void slv_to_string(char* datain, char* dataout, int bytelen) {
+
+  for (int i = 0; i < bytelen; i++) {
+    *dataout = HDL_LOGIC_CHAR[*datain];
+    datain++;
+    dataout++;
+  }
+
+  return;
+
+}
+
+
+void uchar_to_slv(unsigned char* datain, char* dataout, int bytelen) {
+
+  for (int i = 0; i < bytelen; i++) {
+    for (int y = 0; y < 8; y++) {
+      if ((*datain >> y) & 1 == 1) {
+        *dataout = HDL_1 ;
+      } else {
+        *dataout = HDL_0;
+      }
+      dataout++;
+    }
+    datain++;
+  }
+
+  return;
+
+}
+
+
+void handleErrors(void) {
+
+  ERR_print_errors_fp(stderr);
+  abort();
+
+}
+
+
+// Create and initialize the context and nitialize the
+// de/encryption operation with keys and iv.
+// No padding is done
+void init(unsigned char *key, unsigned char *iv, char mode) {
+
+  if (!(ctx = EVP_CIPHER_CTX_new()))
+    handleErrors();
+
+  if (mode) {
+    if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
+      handleErrors();
+  } else {
+    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
+      handleErrors();
+  }
+
+  if(1 != EVP_CIPHER_CTX_set_padding(ctx, 0))
+    handleErrors();
+
+}
+
+
+// Provide the message to be de/encrypted and
+// obtain the encrypted output
+int crypt(char            mode,
+          unsigned char  *input,
+          int             input_len,
+          unsigned char  *output) {
+
+  int len = 0;
+
+  if (mode) {
+    if (1 != EVP_DecryptUpdate(ctx, output, &len, input, input_len))
+      handleErrors();
+  } else {
+    if (1 != EVP_EncryptUpdate(ctx, output, &len, input, input_len))
+      handleErrors();
+  }
+
+  return len;
+
+}
+
+
+// Finalize the de/encryption. No further bytes are written
+// as padding is switched off
+int finalize(char mode) {
+
+  int len = 0;
+  unsigned char data[16];
+
+  if (mode) {
+    if (1 != EVP_DecryptFinal_ex(ctx, data, &len))
+      handleErrors();
+  } else {
+    if (1 != EVP_EncryptFinal_ex(ctx, data, &len))
+      handleErrors();
+  }
+
+  // Clean up
+  EVP_CIPHER_CTX_free(ctx);
+
+  return len;
+
+}
+
+
+void cryptData(char* datain, char* key, char* iv, char mode, char start, char final, char* dataout, int bytelen) {
+
+  int crypt_len;
+  unsigned char c_din[bytelen];
+  unsigned char c_key[bytelen];
+  unsigned char c_iv[bytelen];
+  unsigned char c_dout[bytelen];
+
+  slv_to_uchar(datain, c_din, bytelen);
+  slv_to_uchar(key, c_key, bytelen);
+  slv_to_uchar(iv, c_iv, bytelen);
+
+  if (start) {
+    init(c_key, c_iv, mode);
+  }
+
+  crypt_len = crypt(mode, c_din, bytelen, c_dout);
+
+  if (crypt_len != bytelen) {
+    printf("Warning: encrypt() returned with unexpected length %d\n", crypt_len);
+  }
+
+  if (final) {
+    crypt_len = finalize(mode);
+    if (crypt_len != 0) {
+      printf("Warning: finalize() returned with unexpected length %d\n", crypt_len);
+    }
+  }
+
+  uchar_to_slv(c_dout, dataout, bytelen);
+
+  return;
+
+}
diff --git a/cbcaes/sim/vhdl/tb_cbcaes.tcl b/cbcaes/sim/vhdl/tb_cbcaes.tcl
new file mode 100644
index 0000000..62c39e8
--- /dev/null
+++ b/cbcaes/sim/vhdl/tb_cbcaes.tcl
@@ -0,0 +1,13 @@
+set signals [list]
+lappend signals "top.tb_cbcaes.s_reset"
+lappend signals "top.tb_cbcaes.s_clk"
+lappend signals "top.tb_cbcaes.s_validin"
+lappend signals "top.tb_cbcaes.s_acceptin"
+lappend signals "top.tb_cbcaes.s_start"
+lappend signals "top.tb_cbcaes.s_key"
+lappend signals "top.tb_cbcaes.s_iv"
+lappend signals "top.tb_cbcaes.s_datain"
+lappend signals "top.tb_cbcaes.s_validout"
+lappend signals "top.tb_cbcaes.s_acceptout"
+lappend signals "top.tb_cbcaes.s_dataout"
+set num_added [ gtkwave::addSignalsFromList $signals ]
diff --git a/cbcaes/sim/vhdl/tb_cbcaes.vhd b/cbcaes/sim/vhdl/tb_cbcaes.vhd
new file mode 100644
index 0000000..33766f6
--- /dev/null
+++ b/cbcaes/sim/vhdl/tb_cbcaes.vhd
@@ -0,0 +1,165 @@
+-- ======================================================================
+-- AES Counter mode testbench
+-- Copyright (C) 2020 Torsten Meissner
+-------------------------------------------------------------------------
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of 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.
+
+-- This program 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 a copy of the GNU General Public License
+-- along with this program; if not, write to the Free Software
+-- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+-- ======================================================================
+
+
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+library osvvm;
+  use osvvm.RandomPkg.all;
+
+use std.env.all;
+
+
+entity tb_cbcaes is
+end entity tb_cbcaes;
+
+
+architecture sim of tb_cbcaes is
+
+
+  signal s_reset    : std_logic := '0';
+  signal s_clk      : std_logic := '0';
+
+  signal s_start    : std_logic := '0';
+  signal s_mode     : std_logic := '0';
+  signal s_iv       : std_logic_vector(0 to 127) := (others => '0');
+  signal s_key      : std_logic_vector(0 to 127) := (others => '0');
+  signal s_datain   : std_logic_vector(0 to 127) := (others => '0');
+  signal s_validin  : std_logic := '0';
+  signal s_acceptin : std_logic;
+
+  signal s_dataout   : std_logic_vector(0 to 127);
+  signal s_validout  : std_logic := '0';
+  signal s_acceptout : std_logic := '0';
+
+  procedure cryptData(datain  : in  std_logic_vector(0 to 127);
+                      key     : in  std_logic_vector(0 to 127);
+                      iv      : in  std_logic_vector(0 to 127);
+                      mode    : in  boolean;
+                      start   : in  boolean;
+                      final   : in  boolean;
+                      dataout : out std_logic_vector(0 to 127);
+                      bytelen : in  integer) is
+  begin
+    report "VHPIDIRECT cryptData" severity failure;
+  end procedure;
+
+  attribute foreign of cryptData: procedure is "VHPIDIRECT cryptData";
+
+  function swap (datain : std_logic_vector(0 to 127)) return std_logic_vector is
+    variable v_data : std_logic_vector(0 to 127);
+  begin
+    for i in 0 to 15 loop
+      for y in 0 to 7 loop
+        v_data((i*8)+y) := datain((i*8)+7-y);
+      end loop;
+    end loop;
+    return v_data;
+  end function;
+
+begin
+
+
+  i_cbcaes : entity work.cbcaes
+  port map (
+    reset_i  => s_reset,
+    clk_i    => s_clk,
+    start_i  => s_start,
+    mode_i   => s_mode,
+    key_i    => s_key,
+    iv_i     => s_iv,
+    data_i   => s_datain,
+    valid_i  => s_validin,
+    accept_o => s_acceptin,
+    data_o   => s_dataout,
+    valid_o  => s_validout,
+    accept_i => s_acceptout
+  );
+
+
+  s_clk   <= not(s_clk) after 10 ns;
+  s_reset <= '1' after 100 ns;
+
+
+  process is
+    variable v_key     : std_logic_vector(0 to 127);
+    variable v_iv      : std_logic_vector(0 to 127);
+    variable v_datain  : std_logic_vector(0 to 127);
+    variable v_dataout : std_logic_vector(0 to 127);
+    variable v_random  : RandomPType;
+  begin
+    v_random.InitSeed(v_random'instance_name);
+    wait until s_reset = '1' and rising_edge(s_clk);
+    -- ENCRYPTION TESTs
+    report "Test CBC-AES encryption";
+    s_start <= '1';
+    s_mode  <= '0';
+    v_iv    := v_random.RandSlv(128);
+    v_key   := v_random.RandSlv(128);
+    for i in 0 to 31 loop
+      v_datain  := v_random.RandSlv(128);
+      s_validin <= '1';
+      s_key     <= v_key;
+      s_iv      <= v_iv;
+      s_datain  <= v_datain;
+      cryptData(swap(v_datain), swap(v_key), swap(v_iv), false, i = 0, i = 31, v_dataout, v_datain'length/8);
+      wait until s_acceptin = '1' and rising_edge(s_clk);
+      s_validin <= '0';
+      s_start   <= '0';
+      wait until s_validout = '1' and rising_edge(s_clk);
+      s_acceptout <= '1';
+      assert s_dataout = swap(v_dataout)
+        report "Encryption error: Expected 0x" & to_hstring(swap(v_dataout)) & ", got 0x" & to_hstring(s_dataout)
+        severity failure;
+      wait until rising_edge(s_clk);
+      s_acceptout <= '0';
+    end loop;
+    -- DECRYPTION TESTs
+    report "Test CBC-AES decryption";
+    s_start <= '1';
+    s_mode  <= '1';
+    v_iv    := v_random.RandSlv(128);
+    v_key   := v_random.RandSlv(128);
+    for i in 0 to 31 loop
+      v_datain  := v_random.RandSlv(128);
+      s_validin <= '1';
+      s_key     <= v_key;
+      s_iv      <= v_iv;
+      s_datain  <= v_datain;
+      cryptData(swap(v_datain), swap(v_key), swap(v_iv), true, i = 0, i = 31, v_dataout, v_datain'length/8);
+      wait until s_acceptin = '1' and rising_edge(s_clk);
+      s_validin <= '0';
+      s_start   <= '0';
+      wait until s_validout = '1' and rising_edge(s_clk);
+      s_acceptout <= '1';
+      assert s_dataout = swap(v_dataout)
+        report "Decryption error: Expected 0x" & to_hstring(swap(v_dataout)) & ", got 0x" & to_hstring(s_dataout)
+        severity failure;
+      wait until rising_edge(s_clk);
+      s_acceptout <= '0';
+    end loop;
+    wait for 100 ns;
+    report "Simulation finished without errors";
+    finish(0);
+  end process;
+
+
+end architecture sim;