diff --git a/ion/Makefile b/ion/Makefile
index b21aab92c..595b2a67a 100644
--- a/ion/Makefile
+++ b/ion/Makefile
@@ -1,2 +1,6 @@
 SFLAGS += -Iion/include -DKD_CONFIG_H=1
 include ion/src/$(PLATFORM)/Makefile
+
+tests += $(addprefix ion/test/,\
+  crc32.cpp\
+)
diff --git a/ion/include/ion.h b/ion/include/ion.h
index 77de5fb56..7bcd82748 100644
--- a/ion/include/ion.h
+++ b/ion/include/ion.h
@@ -8,6 +8,8 @@
 #include <ion/keyboard.h>
 #include <ion/led.h>
 #include <ion/power.h>
+#include <stdint.h>
+#include <string.h>
 
 
 /* ION is not your regular library. It is a library you link against, but it
@@ -26,6 +28,10 @@ void usleep(long us);
 /* CAUTION: This is a complete reset! */
 void reset();
 
+// CRC32 : non xor-ed, non reversed, direct, polynomial 4C11DB7
+// Only accepts whole 32bit values
+uint32_t crc32(const uint32_t * data, size_t length);
+
 }
 
 #endif
diff --git a/ion/src/device/device.cpp b/ion/src/device/device.cpp
index 74fac25cb..91f706b93 100644
--- a/ion/src/device/device.cpp
+++ b/ion/src/device/device.cpp
@@ -26,6 +26,21 @@ void Ion::usleep(long us) {
   }
 }
 
+uint32_t Ion::crc32(const uint32_t * data, size_t length) {
+  bool initialCRCEngineState = RCC.AHB1ENR()->getCRCEN();
+  RCC.AHB1ENR()->setCRCEN(true);
+  CRC.CR()->setRESET(true);
+
+  const uint32_t * end = data + length;
+  while (data < end) {
+    CRC.DR()->set(*data++);
+  }
+
+  uint32_t result = CRC.DR()->get();
+  RCC.AHB1ENR()->setCRCEN(initialCRCEngineState);
+  return result;
+}
+
 void Ion::reset() {
   CM4.AIRCR()->requestReset();
 }
diff --git a/ion/src/device/regs/crc.h b/ion/src/device/regs/crc.h
new file mode 100644
index 000000000..6ae4a2c10
--- /dev/null
+++ b/ion/src/device/regs/crc.h
@@ -0,0 +1,27 @@
+#ifndef REGS_CRC_H
+#define REGS_CRC_H
+
+#include "register.h"
+
+class CRC {
+public:
+  class DR : public Register32 {
+  };
+
+  class CR : Register32 {
+  public:
+    REGS_BOOL_FIELD(RESET, 0);
+  };
+
+  constexpr CRC() {};
+  REGS_REGISTER_AT(DR, 0x00);
+  REGS_REGISTER_AT(CR, 0x08);
+private:
+  constexpr uint32_t Base() const {
+    return 0x40023000;
+  };
+};
+
+constexpr CRC CRC;
+
+#endif
diff --git a/ion/src/device/regs/regs.h b/ion/src/device/regs/regs.h
index f030ac281..c37219c36 100644
--- a/ion/src/device/regs/regs.h
+++ b/ion/src/device/regs/regs.h
@@ -2,6 +2,7 @@
 #define REGS_REGS_H
 
 #include "adc.h"
+#include "crc.h"
 #include "exti.h"
 #include "cm4.h"
 #include "fsmc.h"
diff --git a/ion/src/shared/crc32.cpp b/ion/src/shared/crc32.cpp
new file mode 100644
index 000000000..9f2e93d53
--- /dev/null
+++ b/ion/src/shared/crc32.cpp
@@ -0,0 +1,23 @@
+#include <ion.h>
+
+constexpr uint32_t polynomial = 0x04C11DB7;
+
+static uint32_t crc32(uint32_t crc, uint8_t data) {
+    crc ^= data << 24;
+    for (int i=8; i--;) {
+      crc = crc & 0x80000000 ? ((crc<<1)^polynomial) : (crc << 1);
+    }
+    return crc;
+}
+
+uint32_t Ion::crc32(const uint32_t * data, size_t length) {
+  uint32_t crc = 0xFFFFFFFF;
+  for (int i=0; i<length; i++) {
+    // FIXME: Assumes little-endian byte order!
+    crc = ::crc32(crc, (uint8_t)((data[i] >> 24) & 0xFF));
+    crc = ::crc32(crc, (uint8_t)((data[i] >> 16) & 0xFF));
+    crc = ::crc32(crc, (uint8_t)((data[i] >> 8) & 0xFF));
+    crc = ::crc32(crc, (uint8_t)(data[i] & 0xFF));
+  }
+  return crc;
+}
diff --git a/ion/src/simulator/Makefile b/ion/src/simulator/Makefile
index d2e5f6ab2..964468a1d 100644
--- a/ion/src/simulator/Makefile
+++ b/ion/src/simulator/Makefile
@@ -4,6 +4,9 @@ objs += $(addprefix ion/src/simulator/, \
   battery.o\
   init.o\
 )
+objs += $(addprefix ion/src/shared/, \
+  crc32.o\
+)
 objs += $(addprefix ion/src/simulator/boot/, main.o)
 objs += $(addprefix ion/src/simulator/display/, fltklcd.o)
 objs += $(addprefix ion/src/simulator/keyboard/, fltkkbd.o)
diff --git a/ion/test/crc32.cpp b/ion/test/crc32.cpp
new file mode 100644
index 000000000..be5cb1f65
--- /dev/null
+++ b/ion/test/crc32.cpp
@@ -0,0 +1,10 @@
+#include <quiz.h>
+#include <ion.h>
+#include <assert.h>
+
+QUIZ_CASE(ion_crc32) {
+  uint32_t input[] = { 0x48656C6C, 0x6F2C2077 };
+  assert(Ion::crc32(input, 1) == 0x93591FFD);
+  assert(Ion::crc32(input, 2) == 0x72EAD3FB);
+}
+