diff --git a/Arduino_Code/duco_hash.cpp b/Arduino_Code/duco_hash.cpp
index 48113816..7af618a7 100644
--- a/Arduino_Code/duco_hash.cpp
+++ b/Arduino_Code/duco_hash.cpp
@@ -23,10 +23,10 @@ void duco_hash_block(duco_hash_state_t * hasher) {
 
 	for (uint8_t i = 10; i < 80; i++) {
 		if (i >= 16) {
-			w[i & 15] = sha1_rotl(1, w[(i-3) & 15] ^ w[(i-8) & 15] ^ w[(i-14) & 15] ^ w[(i-16) & 15]);
+			w[i & 15] = sha1_rotl(1,w[(i-3) & 15] ^ w[(i-8) & 15] ^ w[(i-14) & 15] ^ w[(i-16) & 15]);
 		}
 
-		uint32_t temp = sha1_rotl(5, a) + e + w[i & 15];
+		uint32_t temp = sha1_rotl5(a) + e + w[i & 15];
 		if (i < 20) {
 			temp += (b & c) | ((~b) & d);
 			temp += 0x5a827999;
@@ -43,7 +43,7 @@ void duco_hash_block(duco_hash_state_t * hasher) {
 
 		e = d;
 		d = c;
-		c = sha1_rotl(30, b);
+		c = sha1_rotl30(b);
 		b = a;
 		a = temp;
 	}
@@ -105,13 +105,13 @@ void duco_hash_init(duco_hash_state_t * hasher, char const * prevHash) {
 	}
 
 	for (uint8_t i = 0; i < 10; i++) {
-		uint32_t temp = sha1_rotl(5, a) + e + w[i & 15];
+		uint32_t temp = sha1_rotl5(a) + e + w[i & 15];
 		temp += (b & c) | ((~b) & d);
 		temp += 0x5a827999;
 
 		e = d;
 		d = c;
-		c = sha1_rotl(30, b);
+		c = sha1_rotl30(b);
 		b = a;
 		a = temp;
 	}
diff --git a/Arduino_Code/duco_hash.h b/Arduino_Code/duco_hash.h
index 462b75a9..055aa780 100644
--- a/Arduino_Code/duco_hash.h
+++ b/Arduino_Code/duco_hash.h
@@ -14,6 +14,16 @@ struct duco_hash_state_t {
 	uint8_t total_bytes;
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+// Declare external assembly functions
+extern uint32_t sha1_rotl5(uint32_t val);
+extern uint32_t sha1_rotl30(uint32_t val);
+#ifdef __cplusplus
+}
+#endif
+
 void duco_hash_init(duco_hash_state_t * hasher, char const * prevHash);
 
 uint8_t const * duco_hash_try_nonce(duco_hash_state_t * hasher, char const * nonce);
diff --git a/Arduino_Code/duco_hash_asm.S b/Arduino_Code/duco_hash_asm.S
new file mode 100644
index 00000000..791e905d
--- /dev/null
+++ b/Arduino_Code/duco_hash_asm.S
@@ -0,0 +1,75 @@
+.global sha1_rotl5
+.global sha1_rotl30
+
+; Input: 
+;   - a value in r25:r22 (little-endian: r22 is LSB, r25 is MSB)
+; Output:
+;   - temp result in r25:r22
+sha1_rotl5:
+    clr r20          ; Will accumulate the 5 carry-out bits
+
+    lsl r22          ; Rotate #1
+    rol r23
+    rol r24
+    rol r25
+    rol r20
+
+    lsl r22          ; Rotate #2
+    rol r23
+    rol r24
+    rol r25
+    rol r20
+
+    lsl r22          ; Rotate #3
+    rol r23
+    rol r24
+    rol r25
+    rol r20
+
+    lsl r22          ; Rotate #4
+    rol r23
+    rol r24
+    rol r25
+    rol r20
+
+    lsl r22          ; Rotate #5
+    rol r23
+    rol r24
+    rol r25
+    rol r20          ; Now r20 contains the 5 bits that wrapped around
+
+    ; r20 now contains bits 31..27 (original MSBs) in its lowest 5 bits
+    ; OR them into r22 (LSB)
+    or r22, r20
+
+    ret
+
+; Input: 32-bit value in r25:r22 (r25=MSB, r22=LSB)
+; Output: Rotated result in r25:r22
+sha1_rotl30:
+    ; Save original bits 0-1 from the LSB (r22) and shift them to positions 6-7.
+    mov   r20, r22       ; r20 = original r22
+    andi  r20, 0x03      ; r20 = (r22 & 0x03)
+    ; Multiply r20 by 64 (i.e. shift left by 6)
+    lsl   r20
+    lsl   r20
+    lsl   r20
+    lsl   r20
+    lsl   r20
+    lsl   r20           ; now r20 = (r22 & 0x03) << 6
+
+    ; Shift the entire 32-bit value right by 2 bits (which is equivalent to rotating left by 30)
+    lsr   r25          ; shift MSB (r25) right by 1; its LSB goes into carry
+    ror   r24          ; rotate r24 right through carry
+    ror   r23          ; rotate r23 right through carry
+    ror   r22          ; rotate r22 right through carry  -- first shift
+
+    lsr   r25          ; second shift: shift r25 right by 1
+    ror   r24
+    ror   r23
+    ror   r22          ; second shift
+
+    ; OR the saved bits into the MSB (r25)
+    or    r25, r20
+
+    ret