diff --git a/aes.c b/aes.c
index 1d94297..cf6bd10 100644
--- a/aes.c
+++ b/aes.c
@@ -21,21 +21,20 @@ void aes128_init(const uint8_t *key) {
     return;
 }
 
-void aes128_ecb(uint8_t *dest, uint8_t const *const in) {
+uint8_t *aes128_ecb(uint8_t const *const in) {
 #ifdef HOST_BUILD
     AES_KEY key;
     AES_set_encrypt_key(g_ecbdata.key, 128, &key);
     AES_encrypt(in, g_ecbdata.out, &key);
 #else
-    memmove(g_ecbdata.in, in, 16);
+    memcpy(g_ecbdata.in, in, 16);
     NRF_ECB->TASKS_STARTECB = 1;
     while (!NRF_ECB->EVENTS_ENDECB) {
         ;
     }
     NRF_ECB->EVENTS_ENDECB = 0;
 #endif /* HOST_BUILD */
-    memmove(dest, g_ecbdata.out, 16);
-    return;
+    return g_ecbdata.out;
 }
 
 #ifdef HOST_BUILD
diff --git a/aes.h b/aes.h
index 3582b02..952f696 100644
--- a/aes.h
+++ b/aes.h
@@ -11,5 +11,5 @@ typedef struct {
 } ecbdata_t;
 
 void aes128_init(const uint8_t *);
-void aes128_ecb(uint8_t *, uint8_t const *const);
+uint8_t *aes128_ecb(uint8_t const *const);
 void aes_dump_state(void);
diff --git a/block.c b/block.c
index 44dcce7..9e19cf4 100644
--- a/block.c
+++ b/block.c
@@ -31,7 +31,7 @@ void block_print_bytes(char const *const label, void const *const v,
 }
 #endif
 
-void block_xor(uint8_t *dest, uint8_t *const a, uint8_t *const b) {
+void block_xor(uint8_t *dest, uint8_t const *const a, uint8_t const *const b) {
     for (uint_fast8_t i = 0; i < 4; i++) {
         *((uint32_t *)dest + i) = *((uint32_t *)a + i) ^ *((uint32_t *)b + i);
     }
diff --git a/block.h b/block.h
index 6ca99b7..64bc195 100644
--- a/block.h
+++ b/block.h
@@ -12,4 +12,4 @@ void block_print(char const *const, void const *const);
 void block_print_bytes(char const *const, void const *const, uint32_t);
 void block_shiftl(uint8_t *, uint8_t *const, uint_fast8_t);
 void block_shiftr(uint8_t *, uint8_t *const, uint_fast8_t);
-void block_xor(uint8_t *, uint8_t *const, uint8_t *const);
+void block_xor(uint8_t *, uint8_t const *const, uint8_t const *const);
diff --git a/cmac.c b/cmac.c
index 01adb6e..3982661 100644
--- a/cmac.c
+++ b/cmac.c
@@ -33,10 +33,9 @@ void cmac_aes128_init(const uint8_t *key) {
 void cmac_aes128_expand_key(uint8_t const *const key, uint8_t *k1,
                             uint8_t *k2) {
     /* Generate two required subkeys according to NIST 800-38B */
-    uint8_t l[16] = {0},
-            Rb[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x87};
+    uint8_t Rb[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x87};
 
-    aes128_ecb(l, zeros);
+    uint8_t *l = aes128_ecb(zeros);
     if ((l[0] >> 7) == 0) {
         block_shiftl(k1, l, 1);
     } else {
@@ -70,7 +69,7 @@ void cmac_aes128(uint8_t *dest, uint8_t *msg, size_t msg_len,
     uint8_t alt_msg[num_blocks * 16],
         *last_block = &alt_msg[(num_blocks - 1) * 16];
     memset(alt_msg, 0, num_blocks * 16);
-    memmove(alt_msg, msg, msg_len);
+    memcpy(alt_msg, msg, msg_len);
 
     if (!last_block_complete) {
         /* Padding is single 1 bit, run out on 0s.. find the next byte,
@@ -81,12 +80,12 @@ void cmac_aes128(uint8_t *dest, uint8_t *msg, size_t msg_len,
         block_xor(last_block, last_block, g_k1);
     }
 
-    uint8_t x[16] = {0}, y[16] = {0};
+    uint8_t *x = (uint8_t *)zeros, y[16] = {0};
 
     for (uint32_t i = 0; i < num_blocks; i++) {
         uint8_t *block = &alt_msg[i * 16];
         block_xor(y, x, block);
-        aes128_ecb(x, y);
+        x = aes128_ecb(y);
     }
     cmac_truncate(dest, x, tag_len);
     return;
diff --git a/ctr.c b/ctr.c
index 040eab2..32026f2 100644
--- a/ctr.c
+++ b/ctr.c
@@ -20,15 +20,15 @@ void aes128_ctr_evolve_counter(void) {
 }
 
 void aes128_ctr(uint8_t *dest, uint8_t *msg, uint32_t msg_len) {
-    uint8_t buffer[16];
+    uint8_t *buffer;
     uint32_t num_blocks = msg_len / 16;
     for (uint32_t i = 0; i < num_blocks; i++) {
-        aes128_ecb(buffer, g_counter);
+        buffer = aes128_ecb(g_counter);
         aes128_ctr_evolve_counter();
         block_xor(dest + (i * 16), msg + (i * 16), buffer);
     }
     if (msg_len % 16) {
-        aes128_ecb(buffer, g_counter);
+        buffer = aes128_ecb(g_counter);
         for (uint8_t i = 0; i < msg_len % 16; i++) {
             dest[num_blocks * 16 + i] = msg[num_blocks * 16 + i] ^ buffer[i];
         }