diff --git a/libavb/avb_crc32.c b/libavb/avb_crc32.c
index 7d4cb09..6b70383 100644
--- a/libavb/avb_crc32.c
+++ b/libavb/avb_crc32.c
@@ -1,114 +1,66 @@
-/*-
- *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
- *  code or tables extracted from it, as desired without restriction.
- */
-
 /*
- *  First, the polynomial itself and its table of feedback terms.  The
- *  polynomial is
- *  X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
+ * Copyright 2020 The Android Open Source Project
  *
- *  Note that we take it "backwards" and put the highest-order term in
- *  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
- *  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
- *  the MSB being 1
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *  Note that the usual hardware shift register implementation, which
- *  is what we're using (we're merely optimizing it by doing eight-bit
- *  chunks at a time) shifts bits into the lowest-order term.  In our
- *  implementation, that means shifting towards the right.  Why do we
- *  do it this way?  Because the calculated CRC must be transmitted in
- *  order from highest-order term to lowest-order term.  UARTs transmit
- *  characters in order from LSB to MSB.  By storing the CRC this way
- *  we hand it to the UART in the order low-byte to high-byte; the UART
- *  sends each low-bit to hight-bit; and the result is transmission bit
- *  by bit from highest- to lowest-order term without requiring any bit
- *  shuffling on our part.  Reception works similarly
+ *     http://www.apache.org/licenses/LICENSE-2.0
  *
- *  The feedback terms table consists of 256, 32-bit entries.  Notes
- *
- *      The table can be generated at runtime if desired; code to do so
- *      is shown later.  It might not be obvious, but the feedback
- *      terms simply represent the results of eight shift/xor opera
- *      tions for all combinations of data and CRC register values
- *
- *      The values must be right-shifted by eight bits by the "updcrc
- *      logic; the shift must be unsigned (bring in zeroes).  On some
- *      hardware you could probably optimize the shift in assembler by
- *      using byte-swap instructions
- *      polynomial $edb88320
- *
- *
- * CRC32 code derived from work by Gary S. Brown.
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
-#include "avb_sysdeps.h"
+/* See https://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks
+ * for info on the general algorithm. We use the following configuration:
+ *   32-bit CRC
+ *   Polynomial = 0x04C11DB7
+ *   MSB-first
+ *   Input and output complement
+ *   Input and output bit reversal
+ *
+ * This implementation optimizes for size and readability. We only need this for
+ * 28 bytes of A/B booting metadata, so efficiency is largely irrelevant whereas
+ * a 1KiB lookup table can be a significant cost for bootloaders.
+ */
+
 #include "avb_util.h"
 
-/* Code taken from FreeBSD 8 */
+/* Lookup table for reversing 4 bits. */
+/* clang-format off */
+static uint8_t reverse_4bit_table[] = {
+  0x0, 0x8, 0x4, 0xC,
+  0x2, 0xA, 0x6, 0xE,
+  0x1, 0x9, 0x5, 0xD,
+  0x3, 0xB, 0x7, 0xF
+};
+/* clang-format on */
 
-static uint32_t iavb_crc32_tab[] = {
-    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
-    0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
-    0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
-    0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
-    0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
-    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
-    0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
-    0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
-    0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
-    0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
-    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
-    0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
-    0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
-    0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
-    0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
-    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
-    0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
-    0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
-    0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
-    0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
-    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
-    0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
-    0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
-    0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
-    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
-    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
-    0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
-    0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
-    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
-    0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
-    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
-    0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
-    0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
-    0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
-    0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
-    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
-    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
-    0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
-    0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
-    0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
-    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
-    0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
-    0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d};
+static uint8_t reverse_byte(uint8_t val) {
+  return (reverse_4bit_table[val & 0xF] << 4) | reverse_4bit_table[val >> 4];
+}
 
-/*
- * A function that calculates the CRC-32 based on the table above is
- * given below for documentation purposes. An equivalent implementation
- * of this function that's actually used in the kernel can be found
- * in sys/libkern.h, where it can be inlined.
- */
-
-static uint32_t iavb_crc32(uint32_t crc_in, const uint8_t* buf, int size) {
-  const uint8_t* p = buf;
-  uint32_t crc;
-
-  crc = crc_in ^ ~0U;
-  while (size--)
-    crc = iavb_crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
-  return crc ^ ~0U;
+static uint32_t reverse_uint32(uint32_t val) {
+  return (reverse_byte(val) << 24) | (reverse_byte(val >> 8) << 16) |
+         (reverse_byte(val >> 16) << 8) | reverse_byte(val >> 24);
 }
 
 uint32_t avb_crc32(const uint8_t* buf, size_t size) {
-  return iavb_crc32(0, buf, size);
+  uint32_t crc = 0xFFFFFFFF;
+
+  for (size_t i = 0; i < size; ++i) {
+    crc = crc ^ ((uint32_t)reverse_byte(buf[i]) << 24);
+    for (int j = 0; j < 8; ++j) {
+      if (crc & 0x80000000) {
+        crc = (crc << 1) ^ 0x04C11DB7;
+      } else {
+        crc <<= 1;
+      }
+    }
+  }
+
+  return reverse_uint32(~crc);
 }