diff --git a/src/crypto/chacha.h b/src/crypto/chacha.h
index 22da53bd0..7a120931a 100644
--- a/src/crypto/chacha.h
+++ b/src/crypto/chacha.h
@@ -69,10 +69,17 @@ namespace crypto {
     chacha20(data, length, key.data(), reinterpret_cast<const uint8_t*>(&iv), cipher);
   }
 
-  inline void generate_chacha_key(const void *data, size_t size, chacha_key& key, int cn_variant = 0, bool prehashed=false) {
+  inline void generate_chacha_key(const void *data, size_t size, chacha_key& key) {
     static_assert(sizeof(chacha_key) <= sizeof(hash), "Size of hash must be at least that of chacha_key");
     tools::scrubbed_arr<char, HASH_SIZE> pwd_hash;
-    crypto::cn_slow_hash_pre(data, size, pwd_hash.data(), cn_variant, prehashed);
+    crypto::cn_slow_hash(data, size, pwd_hash.data(), 0/*variant*/, 0/*prehashed*/);
+    memcpy(&key, pwd_hash.data(), sizeof(key));
+  }
+
+  inline void generate_chacha_key_prehashed(const void *data, size_t size, chacha_key& key) {
+    static_assert(sizeof(chacha_key) <= sizeof(hash), "Size of hash must be at least that of chacha_key");
+    tools::scrubbed_arr<char, HASH_SIZE> pwd_hash;
+    crypto::cn_slow_hash(data, size, pwd_hash.data(), 0/*variant*/, 1/*prehashed*/);
     memcpy(&key, pwd_hash.data(), sizeof(key));
   }
 
diff --git a/src/crypto/hash-ops.h b/src/crypto/hash-ops.h
index 934d464de..d77d55cf3 100644
--- a/src/crypto/hash-ops.h
+++ b/src/crypto/hash-ops.h
@@ -79,8 +79,7 @@ enum {
 };
 
 void cn_fast_hash(const void *data, size_t length, char *hash);
-void cn_slow_hash(const void *data, size_t length, char *hash, int variant);
-void cn_slow_hash_pre(const void *data, size_t length, char *hash, int variant, bool pre);
+void cn_slow_hash(const void *data, size_t length, char *hash, int variant, int prehashed);
 
 void hash_extra_blake(const void *data, size_t length, char *hash);
 void hash_extra_groestl(const void *data, size_t length, char *hash);
diff --git a/src/crypto/hash.h b/src/crypto/hash.h
index bf4f4c096..995e2294e 100644
--- a/src/crypto/hash.h
+++ b/src/crypto/hash.h
@@ -72,7 +72,11 @@ namespace crypto {
   }
 
   inline void cn_slow_hash(const void *data, std::size_t length, hash &hash, int variant = 0) {
-    cn_slow_hash(data, length, reinterpret_cast<char *>(&hash), variant);
+    cn_slow_hash(data, length, reinterpret_cast<char *>(&hash), variant, 0/*prehashed*/);
+  }
+
+  inline void cn_slow_hash_prehashed(const void *data, std::size_t length, hash &hash, int variant = 0) {
+    cn_slow_hash(data, length, reinterpret_cast<char *>(&hash), variant, 1/*prehashed*/);
   }
 
   inline void tree_hash(const hash *hashes, std::size_t count, hash &root_hash) {
diff --git a/src/crypto/slow-hash.c b/src/crypto/slow-hash.c
index 8c7dad8e0..d7dcbd274 100644
--- a/src/crypto/slow-hash.c
+++ b/src/crypto/slow-hash.c
@@ -564,11 +564,7 @@ void slow_hash_free_state(void)
  * @param length the length in bytes of the data
  * @param hash a pointer to a buffer in which the final 256 bit hash will be stored
  */
-void cn_slow_hash(const void *data, size_t length, char *hash, int variant) {
-    cn_slow_hash_pre(data,length,hash,variant,false);
-}
-
-void cn_slow_hash_pre(const void *data, size_t length, char *hash, int variant, bool prehashed)
+void cn_slow_hash(const void *data, size_t length, char *hash, int variant, int prehashed)
 {
     RDATA_ALIGN16 uint8_t expandedKey[240];  /* These buffers are aligned to use later with SSE functions */
 
@@ -909,7 +905,7 @@ STATIC INLINE void aes_pseudo_round_xor(const uint8_t *in, uint8_t *out, const u
 	}
 }
 
-void cn_slow_hash(const void *data, size_t length, char *hash, int variant)
+void cn_slow_hash(const void *data, size_t length, char *hash, int variant, int prehashed)
 {
     RDATA_ALIGN16 uint8_t expandedKey[240];
     RDATA_ALIGN16 uint8_t hp_state[MEMORY];
@@ -932,7 +928,11 @@ void cn_slow_hash(const void *data, size_t length, char *hash, int variant)
 
     /* CryptoNight Step 1:  Use Keccak1600 to initialize the 'state' (and 'text') buffers from the data. */
 
-    hash_process(&state.hs, data, length);
+    if (prehashed) {
+        memcpy(&state.hs, data, length);
+    } else {
+        hash_process(&state.hs, data, length);
+    }
     memcpy(text, state.init, INIT_SIZE_BYTE);
 
     VARIANT1_INIT64();
@@ -1105,7 +1105,7 @@ STATIC INLINE void xor_blocks(uint8_t* a, const uint8_t* b)
   U64(a)[1] ^= U64(b)[1];
 }
 
-void cn_slow_hash(const void *data, size_t length, char *hash, int variant)
+void cn_slow_hash(const void *data, size_t length, char *hash, int variant, int prehashed)
 {
     uint8_t text[INIT_SIZE_BYTE];
     uint8_t a[AES_BLOCK_SIZE];
@@ -1131,7 +1131,11 @@ void cn_slow_hash(const void *data, size_t length, char *hash, int variant)
     long_state = (uint8_t *)malloc(MEMORY);
 #endif
 
-    hash_process(&state.hs, data, length);
+    if (prehashed) {
+        memcpy(&state.hs, data, length);
+    } else {
+        hash_process(&state.hs, data, length);
+    }
     memcpy(text, state.init, INIT_SIZE_BYTE);
 
     VARIANT1_INIT64();
@@ -1289,7 +1293,7 @@ union cn_slow_hash_state {
 };
 #pragma pack(pop)
 
-void cn_slow_hash(const void *data, size_t length, char *hash, int variant) {
+void cn_slow_hash(const void *data, size_t length, char *hash, int variant, int prehashed) {
   uint8_t long_state[MEMORY];
   union cn_slow_hash_state state;
   uint8_t text[INIT_SIZE_BYTE];
@@ -1301,7 +1305,11 @@ void cn_slow_hash(const void *data, size_t length, char *hash, int variant) {
   uint8_t aes_key[AES_KEY_SIZE];
   oaes_ctx *aes_ctx;
 
-  hash_process(&state.hs, data, length);
+  if (prehashed) {
+    memcpy(&state.hs, data, length);
+  } else {
+    hash_process(&state.hs, data, length);
+  }
   memcpy(text, state.init, INIT_SIZE_BYTE);
   memcpy(aes_key, state.hs.b, AES_KEY_SIZE);
   aes_ctx = (oaes_ctx *) oaes_alloc();
diff --git a/src/device/device_ledger.cpp b/src/device/device_ledger.cpp
index ccbc45b45..b3c0035a1 100644
--- a/src/device/device_ledger.cpp
+++ b/src/device/device_ledger.cpp
@@ -513,10 +513,10 @@ namespace hw {
 
         char prekey[200];
         memmove(prekey, &this->buffer_recv[0], 200);
-        crypto::generate_chacha_key(&prekey[0], sizeof(prekey), key, 0, true);
+        crypto::generate_chacha_key_prehashed(&prekey[0], sizeof(prekey), key);
 
         #ifdef DEBUG_HWDEVICE
-        hw::ledger::check32("generate_chacha_key", "key", (char*)key_x.data(), (char*)key.data());
+        hw::ledger::check32("generate_chacha_key_prehashed", "key", (char*)key_x.data(), (char*)key.data());
         #endif
 
         unlock_device();
diff --git a/tests/hash/main.cpp b/tests/hash/main.cpp
index 5a16284df..c7e1fe712 100644
--- a/tests/hash/main.cpp
+++ b/tests/hash/main.cpp
@@ -52,10 +52,10 @@ extern "C" {
     tree_hash((const char (*)[32]) data, length >> 5, hash);
   }
   static void cn_slow_hash_0(const void *data, size_t length, char *hash) {
-    return cn_slow_hash(data, length, hash, 0);
+    return cn_slow_hash(data, length, hash, 0/*variant*/, 0/*prehashed*/);
   }
   static void cn_slow_hash_1(const void *data, size_t length, char *hash) {
-    return cn_slow_hash(data, length, hash, 1);
+    return cn_slow_hash(data, length, hash, 1/*variant*/, 0/*prehashed*/);
   }
 }
 POP_WARNINGS