diff --git a/src/crypto_utils.c b/src/crypto_utils.c
index a9879dd..de60fec 100644
--- a/src/crypto_utils.c
+++ b/src/crypto_utils.c
@@ -25,6 +25,7 @@
 #include "mbedtls/aes.h"
 #include "crypto_utils.h"
 #include "pico_keys.h"
+#include "otp.h"
 
 void double_hash_pin(const uint8_t *pin, uint16_t len, uint8_t output[32]) {
     uint8_t o1[32];
@@ -35,14 +36,28 @@ void double_hash_pin(const uint8_t *pin, uint16_t len, uint8_t output[32]) {
     hash_multi(o1, sizeof(o1), output);
 }
 
-void hash_multi(const uint8_t *input, uint16_t len, uint8_t output[32]) {
+void double_hash_pin_otp(const uint8_t *pin, uint16_t len, uint8_t output[32]) {
+    uint8_t o1[32];
+    hash_multi_otp(pin, len, o1);
+    for (int i = 0; i < sizeof(o1); i++) {
+        o1[i] ^= pin[i % len];
+    }
+    hash_multi_otp(o1, sizeof(o1), output);
+}
+
+void hash_multi_ext(const uint8_t *input, uint16_t len, const uint8_t *init, uint16_t len_init, uint8_t output[32]) {
     mbedtls_sha256_context ctx;
     mbedtls_sha256_init(&ctx);
     uint16_t iters = 256;
     mbedtls_sha256_starts(&ctx, 0);
+    if (init && len_init > 0) {
+        mbedtls_sha256_update(&ctx, init, len_init);
+    }
+    else {
 #ifndef ENABLE_EMULATION
-    mbedtls_sha256_update(&ctx, pico_serial.id, sizeof(pico_serial.id));
+        mbedtls_sha256_update(&ctx, pico_serial.id, sizeof(pico_serial.id));
 #endif
+    }
 
     while (iters > len) {
         mbedtls_sha256_update(&ctx, input, len);
@@ -55,6 +70,18 @@ void hash_multi(const uint8_t *input, uint16_t len, uint8_t output[32]) {
     mbedtls_sha256_free(&ctx);
 }
 
+void hash_multi(const uint8_t *input, uint16_t len, uint8_t output[32]) {
+    hash_multi_ext(input, len, NULL, 0, output);
+}
+
+void hash_multi_otp(const uint8_t *input, uint16_t len, uint8_t output[32]) {
+    if (otp_key_1) {
+        hash_multi_ext(input, len, otp_key_1, 32, output);
+    } else {
+        hash_multi(input, len, output);
+    }
+}
+
 void hash256(const uint8_t *input, size_t len, uint8_t output[32]) {
     mbedtls_sha256_context ctx;
     mbedtls_sha256_init(&ctx);
diff --git a/src/crypto_utils.h b/src/crypto_utils.h
index 413065f..c2e547f 100644
--- a/src/crypto_utils.h
+++ b/src/crypto_utils.h
@@ -39,7 +39,10 @@
 #define IV_SIZE 16
 
 extern void double_hash_pin(const uint8_t *pin, uint16_t len, uint8_t output[32]);
+extern void double_hash_pin_otp(const uint8_t *pin, uint16_t len, uint8_t output[32]);
+extern void hash_multi_ext(const uint8_t *input, uint16_t len, const uint8_t *init, uint16_t len_init, uint8_t output[32]);
 extern void hash_multi(const uint8_t *input, uint16_t len, uint8_t output[32]);
+extern void hash_multi_otp(const uint8_t *input, uint16_t len, uint8_t output[32]);
 extern void hash256(const uint8_t *input, size_t len, uint8_t output[32]);
 extern void generic_hash(mbedtls_md_type_t md, const uint8_t *input, size_t len, uint8_t *output);
 extern int aes_encrypt(const uint8_t *key, const uint8_t *iv, uint16_t key_size, int mode, uint8_t *data, uint16_t len);