diff --git a/SConscript.firmware b/SConscript.firmware
index 3a458cef..6caba9d2 100644
--- a/SConscript.firmware
+++ b/SConscript.firmware
@@ -28,6 +28,7 @@ CPPDEFINES_MOD += [
 ]
 SOURCE_MOD += [
     'embed/extmod/modtrezorcrypto/modtrezorcrypto.c',
+    'embed/extmod/modtrezorcrypto/crc.c',
     'embed/extmod/modtrezorcrypto/rand.c',
     'embed/extmod/modtrezorcrypto/ssss.c',
     'vendor/trezor-crypto/address.c',
diff --git a/SConscript.unix b/SConscript.unix
index 522369ae..00726f96 100644
--- a/SConscript.unix
+++ b/SConscript.unix
@@ -29,6 +29,7 @@ CPPDEFINES_MOD += [
 ]
 SOURCE_MOD += [
     'embed/extmod/modtrezorcrypto/modtrezorcrypto.c',
+    'embed/extmod/modtrezorcrypto/crc.c',
     'embed/extmod/modtrezorcrypto/rand.c',
     'embed/extmod/modtrezorcrypto/ssss.c',
     'vendor/trezor-crypto/address.c',
diff --git a/embed/extmod/modtrezorcrypto/crc.c b/embed/extmod/modtrezorcrypto/crc.c
new file mode 100644
index 00000000..e69785e4
--- /dev/null
+++ b/embed/extmod/modtrezorcrypto/crc.c
@@ -0,0 +1,59 @@
+/*
+ * CRC32 checksum
+ *
+ * Copyright (c) 1998-2003 by Joergen Ibsen / Jibz
+ * All Rights Reserved
+ *
+ * http://www.ibsensoftware.com/
+ *
+ * This software is provided 'as-is', without any express
+ * or implied warranty.  In no event will the authors be
+ * held liable for any damages arising from the use of
+ * this software.
+ *
+ * Permission is granted to anyone to use this software
+ * for any purpose, including commercial applications,
+ * and to alter it and redistribute it freely, subject to
+ * the following restrictions:
+ *
+ * 1. The origin of this software must not be
+ *    misrepresented; you must not claim that you
+ *    wrote the original software. If you use this
+ *    software in a product, an acknowledgment in
+ *    the product documentation would be appreciated
+ *    but is not required.
+ *
+ * 2. Altered source versions must be plainly marked
+ *    as such, and must not be misrepresented as
+ *    being the original software.
+ *
+ * 3. This notice may not be removed or altered from
+ *    any source distribution.
+ */
+
+/*
+ * CRC32 algorithm taken from the zlib source, which is
+ * Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
+ */
+
+#include "crc.h"
+
+static const uint32_t crc32tab[16] = {
+   0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac, 0x76dc4190,
+   0x6b6b51f4, 0x4db26158, 0x5005713c, 0xedb88320, 0xf00f9344,
+   0xd6d6a3e8, 0xcb61b38c, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278,
+   0xbdbdf21c
+};
+
+/* crc is previous value for incremental computation, 0xffffffff initially */
+uint32_t crc32(const uint8_t *data, uint32_t length, uint32_t crc)
+{
+   for (uint32_t i = 0; i < length; ++i) {
+      crc ^= data[i];
+      crc = crc32tab[crc & 0x0f] ^ (crc >> 4);
+      crc = crc32tab[crc & 0x0f] ^ (crc >> 4);
+   }
+
+   // return value suitable for passing in next time, for final value invert it
+   return crc/* ^ 0xffffffff*/;
+}
diff --git a/embed/extmod/modtrezorcrypto/crc.h b/embed/extmod/modtrezorcrypto/crc.h
new file mode 100644
index 00000000..113c898a
--- /dev/null
+++ b/embed/extmod/modtrezorcrypto/crc.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) Pavol Rusnak, SatoshiLabs
+ *
+ * Licensed under TREZOR License
+ * see LICENSE file for details
+ */
+
+#ifndef __CRC_H__
+#define __CRC_H__
+
+#include <stdint.h>
+
+uint32_t crc32(const uint8_t *data, uint32_t length, uint32_t crc);
+
+#endif
diff --git a/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h b/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h
new file mode 100644
index 00000000..1159b158
--- /dev/null
+++ b/embed/extmod/modtrezorcrypto/modtrezorcrypto-crc.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) Pavol Rusnak, SatoshiLabs
+ *
+ * Licensed under TREZOR License
+ * see LICENSE file for details
+ */
+
+#include "py/objstr.h"
+#include "crc.h"
+
+mp_obj_t mod_trezorcrypto_crc_crc32(size_t n_args, const mp_obj_t *args) {
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);
+    uint32_t crc = (n_args > 1) ? mp_obj_get_int_truncated(args[1]) : 0;
+    crc = crc32(bufinfo.buf, bufinfo.len, crc ^ 0xffffffff);
+    return mp_obj_new_int_from_uint(crc ^ 0xffffffff);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorcrypto_crc_crc32_obj, 1, 2, mod_trezorcrypto_crc_crc32);
+
+STATIC const mp_rom_map_elem_t mod_trezorcrypto_crc_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_crc) },
+    { MP_ROM_QSTR(MP_QSTR_crc32), MP_ROM_PTR(&mod_trezorcrypto_crc_crc32_obj) },
+};
+STATIC MP_DEFINE_CONST_DICT(mod_trezorcrypto_crc_globals, mod_trezorcrypto_crc_globals_table);
+
+STATIC const mp_obj_module_t mod_trezorcrypto_crc_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&mod_trezorcrypto_crc_globals,
+};
diff --git a/embed/extmod/modtrezorcrypto/modtrezorcrypto.c b/embed/extmod/modtrezorcrypto/modtrezorcrypto.c
index c1fcb241..959e6210 100644
--- a/embed/extmod/modtrezorcrypto/modtrezorcrypto.c
+++ b/embed/extmod/modtrezorcrypto/modtrezorcrypto.c
@@ -19,13 +19,14 @@
 #include "modtrezorcrypto-blake256.h"
 #include "modtrezorcrypto-blake2b.h"
 #include "modtrezorcrypto-blake2s.h"
+#include "modtrezorcrypto-crc.h"
 #include "modtrezorcrypto-curve25519.h"
 #include "modtrezorcrypto-ed25519.h"
+#include "modtrezorcrypto-nist256p1.h"
 #include "modtrezorcrypto-pbkdf2.h"
 #include "modtrezorcrypto-random.h"
 #include "modtrezorcrypto-rfc6979.h"
 #include "modtrezorcrypto-ripemd160.h"
-#include "modtrezorcrypto-nist256p1.h"
 #include "modtrezorcrypto-secp256k1.h"
 #include "modtrezorcrypto-sha1.h"
 #include "modtrezorcrypto-sha256.h"
@@ -37,24 +38,25 @@
 STATIC const mp_rom_map_elem_t mp_module_trezorcrypto_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_trezorcrypto) },
     { MP_ROM_QSTR(MP_QSTR_AES), MP_ROM_PTR(&mod_trezorcrypto_AES_type) },
+    { MP_ROM_QSTR(MP_QSTR_bip32), MP_ROM_PTR(&mod_trezorcrypto_bip32_module) },
+    { MP_ROM_QSTR(MP_QSTR_bip39), MP_ROM_PTR(&mod_trezorcrypto_bip39_module) },
     { MP_ROM_QSTR(MP_QSTR_blake256), MP_ROM_PTR(&mod_trezorcrypto_Blake256_type) },
     { MP_ROM_QSTR(MP_QSTR_blake2b), MP_ROM_PTR(&mod_trezorcrypto_Blake2b_type) },
     { MP_ROM_QSTR(MP_QSTR_blake2s), MP_ROM_PTR(&mod_trezorcrypto_Blake2s_type) },
+    { MP_ROM_QSTR(MP_QSTR_crc), MP_ROM_PTR(&mod_trezorcrypto_crc_module) },
+    { MP_ROM_QSTR(MP_QSTR_curve25519), MP_ROM_PTR(&mod_trezorcrypto_curve25519_module) },
+    { MP_ROM_QSTR(MP_QSTR_ed25519), MP_ROM_PTR(&mod_trezorcrypto_ed25519_module) },
+    { MP_ROM_QSTR(MP_QSTR_nist256p1), MP_ROM_PTR(&mod_trezorcrypto_nist256p1_module) },
     { MP_ROM_QSTR(MP_QSTR_pbkdf2), MP_ROM_PTR(&mod_trezorcrypto_Pbkdf2_type) },
+    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mod_trezorcrypto_random_module) },
     { MP_ROM_QSTR(MP_QSTR_rfc6979), MP_ROM_PTR(&mod_trezorcrypto_Rfc6979_type) },
     { MP_ROM_QSTR(MP_QSTR_ripemd160), MP_ROM_PTR(&mod_trezorcrypto_Ripemd160_type) },
+    { MP_ROM_QSTR(MP_QSTR_secp256k1), MP_ROM_PTR(&mod_trezorcrypto_secp256k1_module) },
     { MP_ROM_QSTR(MP_QSTR_sha1), MP_ROM_PTR(&mod_trezorcrypto_Sha1_type) },
     { MP_ROM_QSTR(MP_QSTR_sha256), MP_ROM_PTR(&mod_trezorcrypto_Sha256_type) },
     { MP_ROM_QSTR(MP_QSTR_sha512), MP_ROM_PTR(&mod_trezorcrypto_Sha512_type) },
     { MP_ROM_QSTR(MP_QSTR_sha3_256), MP_ROM_PTR(&mod_trezorcrypto_Sha3_256_type) },
     { MP_ROM_QSTR(MP_QSTR_sha3_512), MP_ROM_PTR(&mod_trezorcrypto_Sha3_512_type) },
-    { MP_ROM_QSTR(MP_QSTR_bip32), MP_ROM_PTR(&mod_trezorcrypto_bip32_module) },
-    { MP_ROM_QSTR(MP_QSTR_bip39), MP_ROM_PTR(&mod_trezorcrypto_bip39_module) },
-    { MP_ROM_QSTR(MP_QSTR_curve25519), MP_ROM_PTR(&mod_trezorcrypto_curve25519_module) },
-    { MP_ROM_QSTR(MP_QSTR_ed25519), MP_ROM_PTR(&mod_trezorcrypto_ed25519_module) },
-    { MP_ROM_QSTR(MP_QSTR_nist256p1), MP_ROM_PTR(&mod_trezorcrypto_nist256p1_module) },
-    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mod_trezorcrypto_random_module) },
-    { MP_ROM_QSTR(MP_QSTR_secp256k1), MP_ROM_PTR(&mod_trezorcrypto_secp256k1_module) },
     { MP_ROM_QSTR(MP_QSTR_ssss), MP_ROM_PTR(&mod_trezorcrypto_ssss_module) },
 };
 STATIC MP_DEFINE_CONST_DICT(mp_module_trezorcrypto_globals, mp_module_trezorcrypto_globals_table);
diff --git a/embed/firmware/mpconfigport.h b/embed/firmware/mpconfigport.h
index e6f125f8..19ef5cd4 100644
--- a/embed/firmware/mpconfigport.h
+++ b/embed/firmware/mpconfigport.h
@@ -117,13 +117,13 @@
 
 // extended modules
 #define MICROPY_PY_UCTYPES          (1)
-#define MICROPY_PY_UZLIB            (1)
+#define MICROPY_PY_UZLIB            (0)
 #define MICROPY_PY_UJSON            (0)
 #define MICROPY_PY_URE              (0)
 #define MICROPY_PY_UHEAPQ           (0)
 #define MICROPY_PY_UHASHLIB         (0)
 #define MICROPY_PY_UBINASCII        (1)
-#define MICROPY_PY_UBINASCII_CRC32  (1)
+#define MICROPY_PY_UBINASCII_CRC32  (0)
 #define MICROPY_PY_URANDOM          (0)
 #define MICROPY_PY_URANDOM_EXTRA_FUNCS (0)
 #define MICROPY_PY_USELECT          (0)
diff --git a/embed/unix/mpconfigport.h b/embed/unix/mpconfigport.h
index 995cca39..71720b63 100644
--- a/embed/unix/mpconfigport.h
+++ b/embed/unix/mpconfigport.h
@@ -114,7 +114,7 @@
 #define MICROPY_PY_UTIME_MP_HAL     (1)
 #define MICROPY_PY_UERRNO           (0)
 #define MICROPY_PY_UCTYPES          (1)
-#define MICROPY_PY_UZLIB            (1)
+#define MICROPY_PY_UZLIB            (0)
 #define MICROPY_PY_UJSON            (0)
 #define MICROPY_PY_URE              (0)
 #define MICROPY_PY_UHEAPQ           (0)
@@ -124,7 +124,7 @@
 #define MICROPY_PY_UHASHLIB_SHA1    (0)
 #endif
 #define MICROPY_PY_UBINASCII        (1)
-#define MICROPY_PY_UBINASCII_CRC32  (1)
+#define MICROPY_PY_UBINASCII_CRC32  (0)
 #define MICROPY_PY_URANDOM          (0)
 #ifndef MICROPY_PY_USELECT_POSIX
 #define MICROPY_PY_USELECT_POSIX    (0)
diff --git a/src/trezor/crypto/__init__.py b/src/trezor/crypto/__init__.py
index be6b0aa0..87a7e5e8 100644
--- a/src/trezor/crypto/__init__.py
+++ b/src/trezor/crypto/__init__.py
@@ -1,5 +1,6 @@
 from trezorcrypto import bip32
 from trezorcrypto import bip39
+from trezorcrypto import crc
 from trezorcrypto import pbkdf2
 from trezorcrypto import random
 from trezorcrypto import rfc6979
diff --git a/tests/.gitignore b/tests/.gitignore
new file mode 100644
index 00000000..ceddaa37
--- /dev/null
+++ b/tests/.gitignore
@@ -0,0 +1 @@
+.cache/
diff --git a/tests/test_trezor.crypto.crc.py b/tests/test_trezor.crypto.crc.py
new file mode 100644
index 00000000..01abcd89
--- /dev/null
+++ b/tests/test_trezor.crypto.crc.py
@@ -0,0 +1,23 @@
+from common import *
+
+from trezor.crypto import crc
+from ubinascii import unhexlify
+
+
+class TestCryptoCrc(unittest.TestCase):
+
+    vectors_crc32 = [
+        ('123456789', 0xCBF43926),
+        (unhexlify('0000000000000000000000000000000000000000000000000000000000000000'), 0x190A55AD),
+        (unhexlify('FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF'), 0xFF6CAB0B),
+        (unhexlify('000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F'), 0x91267E8A),
+        ('The quick brown fox jumps over the lazy dog', 0x414FA339),
+    ]
+
+    def test_crc32(self):
+        for i, o in self.vectors_crc32:
+            self.assertEqual(crc.crc32(i), o)
+
+
+if __name__ == '__main__':
+    unittest.main()