diff --git a/app/src/common/parser_common.h b/app/src/common/parser_common.h
index d0973bb..2426cd2 100644
--- a/app/src/common/parser_common.h
+++ b/app/src/common/parser_common.h
@@ -66,6 +66,8 @@ typedef enum {
     parser_unexpected_chain,
     parser_missing_field,
     paser_unknown_transaction,
+
+    parser_invalid_tx_version,
 } parser_error_t;
 
 typedef struct {
diff --git a/app/src/crypto_helper.c b/app/src/crypto_helper.c
index 87c23c3..02fb367 100644
--- a/app/src/crypto_helper.c
+++ b/app/src/crypto_helper.c
@@ -105,19 +105,17 @@ parser_error_t transaction_signature_hash(parser_tx_t *txObj, uint8_t output[HAS
 #endif
 
     // Spends
-    const uint16_t SPENDLEN = 32 + 192 + 32 + 32 + 4 + 32 + 64;
     for (uint64_t i = 0; i < txObj->spends.elements; i++) {
-        const uint8_t *spend_i = txObj->spends.data.ptr + (SPENDLEN * i) + 32;
+        const uint8_t *spend_i = txObj->spends.data.ptr + (SPENDLEN * i) + PUBKEY_RANDONMESS_LEN;
         // Don't hash neither public_key_randomness(32) nor binding_signature(64)
 #if defined(LEDGER_SPECIFIC)
-        ASSERT_CX_OK(cx_blake2b_update(&ctx, spend_i, SPENDLEN - (32 + 64)));
+        ASSERT_CX_OK(cx_blake2b_update(&ctx, spend_i, SPENDLEN - (PUBKEY_RANDONMESS_LEN + BINDING_SIGNATURE_LEN)));
 #else
-        blake2b_update(&state, spend_i, SPENDLEN - (32 + 64));
+        blake2b_update(&state, spend_i, SPENDLEN - (PUBKEY_RANDONMESS_LEN + BINDING_SIGNATURE_LEN));
 #endif
     }
 
     // Outputs
-    const uint16_t OUTPUTLEN = 192 + 328;
     for (uint64_t i = 0; i < txObj->outputs.elements; i++) {
         const uint8_t *output_i = txObj->outputs.data.ptr + (OUTPUTLEN * i);
 #if defined(LEDGER_SPECIFIC)
@@ -128,7 +126,6 @@ parser_error_t transaction_signature_hash(parser_tx_t *txObj, uint8_t output[HAS
     }
 
     // Mints
-    const uint16_t MINTLEN = 32 + 192 + 193 + 8;
     uint16_t tmpOffset = 0;
     for (uint64_t i = 0; i < txObj->mints.elements; i++) {
         const uint8_t *mint_i = txObj->mints.data.ptr + tmpOffset;  // + 32;
@@ -137,16 +134,16 @@ parser_error_t transaction_signature_hash(parser_tx_t *txObj, uint8_t output[HAS
 
 // Don't hash neither public_key_randomness(32) nor binding_signature(64)
 #if defined(LEDGER_SPECIFIC)
-        ASSERT_CX_OK(cx_blake2b_update(&ctx, mint_i + 32, tmpMintLen - (32 + 64)));
+        ASSERT_CX_OK(cx_blake2b_update(&ctx, mint_i + PUBKEY_RANDONMESS_LEN,
+                                       tmpMintLen - (PUBKEY_RANDONMESS_LEN + BINDING_SIGNATURE_LEN)));
 #else
-        blake2b_update(&state, mint_i + 32, tmpMintLen - (32 + 64));
+        blake2b_update(&state, mint_i + PUBKEY_RANDONMESS_LEN, tmpMintLen - (PUBKEY_RANDONMESS_LEN + BINDING_SIGNATURE_LEN));
 #endif
 
         tmpOffset += tmpMintLen;
     }
 
     // Burns
-    const uint16_t BURNLEN = 32 + 8;
     for (uint64_t i = 0; i < txObj->burns.elements; i++) {
         const uint8_t *burn_i = txObj->burns.data.ptr + (BURNLEN * i);
 #if defined(LEDGER_SPECIFIC)
@@ -175,16 +172,16 @@ static parser_error_t h_star(bytes_t a, const uint8_t randomizedPublicKey[32], c
     ASSERT_CX_OK(cx_blake2b_init2_no_throw(&ctx, BLAKE2B_OUTPUT_LEN, NULL, 0, (uint8_t *)SIGNING_REDJUBJUB,
                                            sizeof(SIGNING_REDJUBJUB)));
     ASSERT_CX_OK(cx_blake2b_update(&ctx, a.ptr, a.len));
-    ASSERT_CX_OK(cx_blake2b_update(&ctx, randomizedPublicKey, 32));
-    ASSERT_CX_OK(cx_blake2b_update(&ctx, transactionHash, 32));
+    ASSERT_CX_OK(cx_blake2b_update(&ctx, randomizedPublicKey, PUBKEY_RANDONMESS_LEN));
+    ASSERT_CX_OK(cx_blake2b_update(&ctx, transactionHash, HASH_LEN));
     cx_blake2b_final(&ctx, hash);
 #else
     blake2b_state state = {0};
     blake2b_init_with_personalization(&state, BLAKE2B_OUTPUT_LEN, (const uint8_t *)SIGNING_REDJUBJUB,
                                       sizeof(SIGNING_REDJUBJUB));
     blake2b_update(&state, a.ptr, a.len);
-    blake2b_update(&state, randomizedPublicKey, 32);
-    blake2b_update(&state, transactionHash, 32);
+    blake2b_update(&state, randomizedPublicKey, PUBKEY_RANDONMESS_LEN);
+    blake2b_update(&state, transactionHash, HASH_LEN);
     blake2b_final(&state, hash, BLAKE2B_OUTPUT_LEN);
 #endif
 
diff --git a/app/src/parser_impl.c b/app/src/parser_impl.c
index d55dc78..f89d8c1 100644
--- a/app/src/parser_impl.c
+++ b/app/src/parser_impl.c
@@ -31,7 +31,7 @@ static parser_error_t readTransactionVersion(parser_context_t *ctx, transaction_
     CHECK_ERROR(readByte(ctx, &tmpVersion));
 
     if (tmpVersion != V1 && tmpVersion != V2) {
-        return parser_value_out_of_range;
+        return parser_invalid_tx_version;
     }
     *txVersion = (transaction_version_e)tmpVersion;
     return parser_ok;
@@ -42,7 +42,6 @@ static parser_error_t readSpends(parser_context_t *ctx, vec_spend_description_t
         return parser_no_data;
     }
 
-    const uint16_t SPENDLEN = 32 + 192 + 32 + 32 + 4 + 32 + 64;
     spends->data.ptr = ctx->buffer + ctx->offset;
     spends->data.len = 0;
     const uint8_t *tmpPtr = NULL;
@@ -57,7 +56,7 @@ static parser_error_t readOutputs(parser_context_t *ctx, vec_output_description_
     if (ctx == NULL || outputs == NULL) {
         return parser_no_data;
     }
-    const uint16_t OUTPUTLEN = 192 + 328;
+
     outputs->data.ptr = ctx->buffer + ctx->offset;
     outputs->data.len = 0;
     const uint8_t *tmpPtr = NULL;
@@ -73,7 +72,6 @@ static parser_error_t readMints(parser_context_t *ctx, vec_mint_description_t *m
         return parser_no_data;
     }
 
-    const uint16_t MINTLEN = 32 + 192 + 193 + 8;
     mints->data.ptr = ctx->buffer + ctx->offset;
     mints->data.len = 0;
     const uint8_t *tmpPtr = NULL;
@@ -97,7 +95,6 @@ static parser_error_t readBurns(parser_context_t *ctx, vec_burn_description_t *b
         return parser_no_data;
     }
 
-    const uint16_t BURNLEN = 32 + 8;
     burns->data.ptr = ctx->buffer + ctx->offset;
     burns->data.len = 0;
     const uint8_t *tmpPtr = NULL;
@@ -110,10 +107,14 @@ static parser_error_t readBurns(parser_context_t *ctx, vec_burn_description_t *b
 
 parser_error_t _read(parser_context_t *ctx, parser_tx_t *v) {
     CHECK_ERROR(readTransactionVersion(ctx, &v->transactionVersion));
+
+    // Now read the number of spends, outputs, mints and burns
     CHECK_ERROR(readUint64(ctx, &v->spends.elements));
     CHECK_ERROR(readUint64(ctx, &v->outputs.elements));
     CHECK_ERROR(readUint64(ctx, &v->mints.elements));
     CHECK_ERROR(readUint64(ctx, &v->burns.elements));
+
+    // now read the fee and expiration
     CHECK_ERROR(readInt64(ctx, &v->fee));
     CHECK_ERROR(readUint32(ctx, &v->expiration));
 
diff --git a/app/src/parser_txdef.h b/app/src/parser_txdef.h
index ba06b19..7a2303a 100644
--- a/app/src/parser_txdef.h
+++ b/app/src/parser_txdef.h
@@ -25,8 +25,31 @@ extern "C" {
 // Move bytes_t definition to a different place?
 #include "keys_def.h"
 
-#define NAME_LENGTH     32
-#define METADATA_LENGTH 96
+#define NAME_LENGTH           32
+#define METADATA_LENGTH       96
+#define PUBKEY_RANDONMESS_LEN 32
+#define BINDING_SIGNATURE_LEN 64
+
+// 32-bytes public_key randomness
+// 192-byes proof
+// 32-bytes value_commitment
+// 32-bytes root hash
+// 4-bytes tree_size
+// 32-bytes nullifier
+// 64-bytes authorize signatures
+#define SPENDLEN 32 + 192 + 32 + 32 + 4 + 32 + 64
+
+// 192-bytes proof + 328-bytes Merkle Note
+#define OUTPUTLEN 192 + 328
+
+// 33-bytes public_key randomness
+// 192-byes proof
+// 193-bytes asset_len (creator addr(32) + name (32) + metadata (96) + nonce (1))
+// 8-bytes value
+// + optional values 32 bytes owner, opion flag + 32_bytes new owner
+#define MINTLEN 32 + 192 + 193 + 8
+
+#define BURNLEN 32 + 8
 
 typedef enum {
     V1 = 1,