diff --git a/Makefile b/Makefile
index df9129c..e9d02a2 100644
--- a/Makefile
+++ b/Makefile
@@ -79,7 +79,7 @@ VARIANT_PARAM = COIN
 VARIANT_VALUES = KAS
 
 # Enabling DEBUG flag will enable PRINTF and disable optimizations
-DEBUG = 1
+#DEBUG = 1
 
 ########################################
 #     Application custom permissions   #
diff --git a/doc/COMMANDS.md b/doc/COMMANDS.md
index f15e093..0aa991c 100644
--- a/doc/COMMANDS.md
+++ b/doc/COMMANDS.md
@@ -173,5 +173,11 @@ Transactions signed with ECDSA are currently not supported.
 | 0xB00A | `SW_WRONG_BIP32_COIN_TYPE` | `Coin Type` must be `111111'` |
 | 0xB00B | `SW_WRONG_BIP32_TYPE` | `Type` passed is not valid. Must be either `0`  for `Receive` or `1`  for `Change`|
 | 0xB00C | `SW_WRONG_BIP32_PATH_LEN` | Path length must be `5` |
-| 0xB00D | `SW_MESSAGE_TOO_LONG` | Message len greater than max |
+| 0xB010 | `SW_MESSAGE_PARSING_FAIL` | Unable to parse message data |
+| 0xB011 | `SW_MESSAGE_TOO_LONG` | Message len greater than max |
+| 0xB012 | `SW_MESSAGE_TOO_SHORT` | Message len is 0 |
+| 0xB013 | `SW_MESSAGE_ADDRESS_TYPE_FAIL` | Address type could not be parsed or is not `0`/`1` |
+| 0xB014 | `SW_MESSAGE_ADDRESS_INDEX_FAIL` | Address index could not be parsed |
+| 0xB015 | `SW_MESSAGE_LEN_PARSING_FAIL` | Message length could not be parsed |
+| 0xB016 | `SW_MESSAGE_UNEXPECTED` | Unexpected error while parsing message |
 | 0x9000 | `OK` | Success |
diff --git a/fuzzing/fuzz_tx_parser.cc b/fuzzing/fuzz_tx_parser.cc
index 04fa0b1..4179b83 100644
--- a/fuzzing/fuzz_tx_parser.cc
+++ b/fuzzing/fuzz_tx_parser.cc
@@ -28,7 +28,7 @@
 
 extern "C" {
 #include "buffer.h"
-#include "common/format.h"
+#include "common/format_local.h"
 #include "transaction/deserialize.h"
 #include "transaction/types.h"
 }
diff --git a/fuzzing/fuzz_txin_parser.cc b/fuzzing/fuzz_txin_parser.cc
index cfdb234..5bc030f 100644
--- a/fuzzing/fuzz_txin_parser.cc
+++ b/fuzzing/fuzz_txin_parser.cc
@@ -28,7 +28,7 @@
 
 extern "C" {
 #include "buffer.h"
-#include "common/format.h"
+#include "common/format_local.h"
 #include "transaction/deserialize.h"
 #include "transaction/types.h"
 }
diff --git a/fuzzing/fuzz_txout_parser.cc b/fuzzing/fuzz_txout_parser.cc
index 9b70ea3..cee3e4a 100644
--- a/fuzzing/fuzz_txout_parser.cc
+++ b/fuzzing/fuzz_txout_parser.cc
@@ -28,7 +28,7 @@
 
 extern "C" {
 #include "buffer.h"
-#include "common/format.h"
+#include "common/format_local.h"
 #include "transaction/deserialize.h"
 #include "transaction/types.h"
 }
diff --git a/src/common/format.c b/src/common/format.c
deleted file mode 100644
index d614b61..0000000
--- a/src/common/format.c
+++ /dev/null
@@ -1,187 +0,0 @@
-/*****************************************************************************
- * MIT License
- *
- * Copyright (c) 2023 coderofstuff
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- *****************************************************************************/
-
-#include <stddef.h>   // size_t
-#include <stdint.h>   // int*_t, uint*_t
-#include <string.h>   // strncpy, memmove
-#include <stdbool.h>  // bool
-
-#include "format.h"
-
-bool format_i64(char *dst, size_t dst_len, const int64_t value) {
-    char temp[] = "-9223372036854775808";
-
-    char *ptr = temp;
-    int64_t num = value;
-    int sign = 1;
-
-    if (value < 0) {
-        sign = -1;
-    }
-
-    while (num != 0) {
-        *ptr++ = '0' + (num % 10) * sign;
-        num /= 10;
-    }
-
-    if (value < 0) {
-        *ptr++ = '-';
-    } else if (value == 0) {
-        *ptr++ = '0';
-    }
-
-    int distance = (ptr - temp) + 1;
-
-    if ((int) dst_len < distance) {
-        return false;
-    }
-
-    size_t index = 0;
-
-    while (--ptr >= temp) {
-        dst[index++] = *ptr;
-    }
-
-    dst[index] = '\0';
-
-    return true;
-}
-
-bool format_u64(char *out, size_t outLen, uint64_t in) {
-    uint8_t i = 0;
-
-    if (outLen == 0) {
-        return false;
-    }
-    outLen--;
-
-    while (in > 9) {
-        out[i] = in % 10 + '0';
-        in /= 10;
-        i++;
-        if (i + 1 > outLen) {
-            return false;
-        }
-    }
-    out[i] = in + '0';
-    out[i + 1] = '\0';
-
-    uint8_t j = 0;
-    char tmp;
-
-    // revert the string
-    while (j < i) {
-        // swap out[j] and out[i]
-        tmp = out[j];
-        out[j] = out[i];
-        out[i] = tmp;
-
-        i--;
-        j++;
-    }
-    return true;
-}
-
-bool format_fpu64_trimmed(char *dst, size_t dst_len, const uint64_t value, uint8_t decimals) {
-    char buffer[21] = {0};
-
-    if (!format_u64(buffer, sizeof(buffer), value)) {
-        return false;
-    }
-
-    if (value == 0) {
-        if (dst_len <= 1) {
-            return false;
-        }
-
-        dst[0] = '0';
-        dst[1] = '\0';
-
-        return true;
-    }
-
-    size_t digits = strlen(buffer);
-    size_t offset = 0;
-
-    while (offset < decimals && digits > offset + 1 && buffer[digits - offset - 1] == '0') {
-        buffer[digits - offset - 1] = '\0';
-        offset++;
-    }
-
-    digits -= offset;
-    decimals -= offset;
-
-    if (decimals == 0) {
-        strncpy(dst, buffer, dst_len);
-    } else if (digits <= decimals) {
-        if (dst_len <= 2 + decimals - digits) {
-            return false;
-        }
-        *dst++ = '0';
-        *dst++ = '.';
-        for (uint16_t i = 0; i < decimals - digits; i++, dst++) {
-            *dst = '0';
-        }
-        dst_len -= 2 + decimals - digits;
-        strncpy(dst, buffer, dst_len);
-    } else {
-        if (dst_len <= digits + 1 + decimals) {
-            return false;
-        }
-
-        const size_t shift = digits - decimals;
-        memmove(dst, buffer, shift);
-        dst[shift] = '.';
-        strncpy(dst + shift + 1, buffer + shift, decimals);
-    }
-
-    return true;
-}
-
-int format_hex(const uint8_t *in, size_t in_len, char *out, size_t out_len) {
-    if (out_len < 2 * in_len + 1) {
-        return -1;
-    }
-
-    const char hex[] = "0123456789ABCDEF";
-    size_t i = 0;
-    int written = 0;
-
-    while (i < in_len && (i * 2 + (2 + 1)) <= out_len) {
-        uint8_t high_nibble = (in[i] & 0xF0) >> 4;
-        *out = hex[high_nibble];
-        out++;
-
-        uint8_t low_nibble = in[i] & 0x0F;
-        *out = hex[low_nibble];
-        out++;
-
-        i++;
-        written += 2;
-    }
-
-    *out = '\0';
-
-    return written + 1;
-}
diff --git a/src/common/format.h b/src/common/format.h
deleted file mode 100644
index 1c8d486..0000000
--- a/src/common/format.h
+++ /dev/null
@@ -1,92 +0,0 @@
-/*****************************************************************************
- * MIT License
- *
- * Copyright (c) 2023 coderofstuff
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- *****************************************************************************/
-#pragma once
-
-#include <stddef.h>   // size_t
-#include <stdint.h>   // int*_t, uint*_t
-#include <stdbool.h>  // bool
-
-/**
- * Format 64-bit signed integer as string.
- *
- * @param[out] dst
- *   Pointer to output string.
- * @param[in]  dst_len
- *   Length of output string.
- * @param[in]  value
- *   64-bit signed integer to format.
- *
- * @return true if success, false otherwise.
- *
- */
-bool format_i64(char *dst, size_t dst_len, const int64_t value);
-
-/**
- * Format 64-bit unsigned integer as string.
- *
- * @param[out] dst
- *   Pointer to output string.
- * @param[in]  dst_len
- *   Length of output string.
- * @param[in]  value
- *   64-bit unsigned integer to format.
- *
- * @return true if success, false otherwise.
- *
- */
-bool format_u64(char *dst, size_t dst_len, uint64_t value);
-
-/**
- * Format 64-bit unsigned integer as string with decimals.
- *
- * @param[out] dst
- *   Pointer to output string.
- * @param[in]  dst_len
- *   Length of output string.
- * @param[in]  value
- *   64-bit unsigned integer to format.
- * @param[in]  decimals
- *   Number of digits after decimal separator.
- *
- * @return true if success, false otherwise.
- *
- */
-bool format_fpu64_trimmed(char *dst, size_t dst_len, const uint64_t value, uint8_t decimals);
-
-/**
- * Format byte buffer to uppercase hexadecimal string.
- *
- * @param[in]  in
- *   Pointer to input byte buffer.
- * @param[in]  in_len
- *   Length of input byte buffer.
- * @param[out] out
- *   Pointer to output string.
- * @param[in]  out_len
- *   Length of output string.
- *
- * @return number of bytes written if success, -1 otherwise.
- *
- */
-int format_hex(const uint8_t *in, size_t in_len, char *out, size_t out_len);
diff --git a/src/common/format_local.c b/src/common/format_local.c
new file mode 100644
index 0000000..bea7994
--- /dev/null
+++ b/src/common/format_local.c
@@ -0,0 +1,60 @@
+/*****************************************************************************
+ * MIT License
+ *
+ * Copyright (c) 2023 coderofstuff
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *****************************************************************************/
+
+#include <stddef.h>   // size_t
+#include <stdint.h>   // int*_t, uint*_t
+#include <string.h>   // strncpy, memmove
+#include <stdbool.h>  // bool
+#include <stdio.h>    // sprintf, snprintf
+#include <ctype.h>    // isprint, isspace
+
+#include "./format_local.h"
+
+void format_message_to_sign(char* msg_dest, int msg_dest_len, char* msg_src, int msg_src_len) {
+    int c;
+    int dest_idx = 0;
+
+    for (int i = 0; i < msg_src_len && dest_idx < msg_dest_len; i++) {
+        c = msg_src[i];
+        if (isspace(c))  // to replace all white-space characters as spaces
+        {
+            c = ' ';
+        }
+        if (isprint(c)) {
+            sprintf(msg_dest + dest_idx, "%c", (char) c);
+            dest_idx++;
+        } else {
+            int remaining_buffer_length = msg_dest_len - dest_idx - 1;
+            if (remaining_buffer_length >= 4)  // 4 being the fixed length of \x00
+            {
+                snprintf(msg_dest + dest_idx, remaining_buffer_length, "\\x%02x", c);
+                dest_idx += 4;
+            } else {
+                // fill the rest of the UI buffer spaces, to consider the buffer full
+                memset(msg_dest + dest_idx, ' ', remaining_buffer_length);
+                dest_idx += remaining_buffer_length;
+            }
+        }
+    }
+}
diff --git a/src/common/macros.h b/src/common/format_local.h
similarity index 68%
rename from src/common/macros.h
rename to src/common/format_local.h
index cc8f3d3..5fb8fca 100644
--- a/src/common/macros.h
+++ b/src/common/format_local.h
@@ -23,7 +23,21 @@
  *****************************************************************************/
 #pragma once
 
+#include <stddef.h>   // size_t
+#include <stdint.h>   // int*_t, uint*_t
+#include <stdbool.h>  // bool
+
 /**
- * Macro for the size of a specific structure field.
+ * Calculate the fees by checking the difference between inputs and outputs
+ * @param[out] msg_dest
+ *   Pointer to formatted message destination
+ * @param[out] msg_dest_len
+ *   Length of message destination.
+ * @param[in] msg_src
+ *   Pointer to message source to format.
+ * @param[in] msg_src_len
+ *   Length of message source.
+ *
+ * @return number of bytes written if success, -1 otherwise.
  */
-#define MEMBER_SIZE(type, member) (sizeof(((type *) 0)->member))
+void format_message_to_sign(char* msg_dest, int msg_dest_len, char* msg_src, int msg_src_len);
diff --git a/src/common/write.c b/src/common/write.c
deleted file mode 100644
index 0c0eccc..0000000
--- a/src/common/write.c
+++ /dev/null
@@ -1,72 +0,0 @@
-/*****************************************************************************
- * MIT License
- *
- * Copyright (c) 2023 coderofstuff
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- *****************************************************************************/
-
-#include <stdint.h>  // uint*_t
-#include <stddef.h>  // size_t
-
-void write_u16_be(uint8_t *ptr, size_t offset, uint16_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 8);
-    ptr[offset + 1] = (uint8_t)(value >> 0);
-}
-
-void write_u32_be(uint8_t *ptr, size_t offset, uint32_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 24);
-    ptr[offset + 1] = (uint8_t)(value >> 16);
-    ptr[offset + 2] = (uint8_t)(value >> 8);
-    ptr[offset + 3] = (uint8_t)(value >> 0);
-}
-
-void write_u64_be(uint8_t *ptr, size_t offset, uint64_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 56);
-    ptr[offset + 1] = (uint8_t)(value >> 48);
-    ptr[offset + 2] = (uint8_t)(value >> 40);
-    ptr[offset + 3] = (uint8_t)(value >> 32);
-    ptr[offset + 4] = (uint8_t)(value >> 24);
-    ptr[offset + 5] = (uint8_t)(value >> 16);
-    ptr[offset + 6] = (uint8_t)(value >> 8);
-    ptr[offset + 7] = (uint8_t)(value >> 0);
-}
-
-void write_u16_le(uint8_t *ptr, size_t offset, uint16_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 0);
-    ptr[offset + 1] = (uint8_t)(value >> 8);
-}
-
-void write_u32_le(uint8_t *ptr, size_t offset, uint32_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 0);
-    ptr[offset + 1] = (uint8_t)(value >> 8);
-    ptr[offset + 2] = (uint8_t)(value >> 16);
-    ptr[offset + 3] = (uint8_t)(value >> 24);
-}
-
-void write_u64_le(uint8_t *ptr, size_t offset, uint64_t value) {
-    ptr[offset + 0] = (uint8_t)(value >> 0);
-    ptr[offset + 1] = (uint8_t)(value >> 8);
-    ptr[offset + 2] = (uint8_t)(value >> 16);
-    ptr[offset + 3] = (uint8_t)(value >> 24);
-    ptr[offset + 4] = (uint8_t)(value >> 32);
-    ptr[offset + 5] = (uint8_t)(value >> 40);
-    ptr[offset + 6] = (uint8_t)(value >> 48);
-    ptr[offset + 7] = (uint8_t)(value >> 56);
-}
diff --git a/src/common/write.h b/src/common/write.h
deleted file mode 100644
index ad73955..0000000
--- a/src/common/write.h
+++ /dev/null
@@ -1,105 +0,0 @@
-/*****************************************************************************
- * MIT License
- *
- * Copyright (c) 2023 coderofstuff
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- *****************************************************************************/
-#pragma once
-
-#include <stdint.h>  // uint*_t
-#include <stddef.h>  // size_t
-
-/**
- * Write 16-bit unsigned integer value as Big Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   16-bit unsigned integer to write in output byte buffer as Big Endian.
- *
- */
-void write_u16_be(const uint8_t *ptr, size_t offset, uint16_t value);
-
-/**
- * Write 32-bit unsigned integer value as Big Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   32-bit unsigned integer to write in output byte buffer as Big Endian.
- *
- */
-void write_u32_be(uint8_t *ptr, size_t offset, uint32_t value);
-
-/**
- * Write 64-bit unsigned integer value as Big Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   64-bit unsigned integer to write in output byte buffer as Big Endian.
- *
- */
-void write_u64_be(uint8_t *ptr, size_t offset, uint64_t value);
-
-/**
- * Write 16-bit unsigned integer value as Little Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   16-bit unsigned integer to write in output byte buffer as Little Endian.
- *
- */
-void write_u16_le(uint8_t *ptr, size_t offset, uint16_t value);
-
-/**
- * Write 32-bit unsigned integer value as Little Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   32-bit unsigned integer to write in output byte buffer as Little Endian.
- *
- */
-void write_u32_le(uint8_t *ptr, size_t offset, uint32_t value);
-
-/**
- * Write 64-bit unsigned integer value as Little Endian.
- *
- * @param[out] ptr
- *   Pointer to output byte buffer.
- * @param[in]  offset
- *   Offset in the output byte buffer.
- * @param[in]  value
- *   64-bit unsigned integer to write in output byte buffer as Little Endian.
- *
- */
-void write_u64_le(uint8_t *ptr, size_t offset, uint64_t value);
diff --git a/src/handler/sign_msg.c b/src/handler/sign_msg.c
index 5700235..5005842 100644
--- a/src/handler/sign_msg.c
+++ b/src/handler/sign_msg.c
@@ -50,16 +50,24 @@ int handler_sign_msg(buffer_t *cdata) {
     G_context.state = STATE_NONE;
 
     if (!buffer_read_u8(cdata, &G_context.msg_info.address_type)) {
-        return io_send_sw(SW_WRONG_DATA_LENGTH);
+        return io_send_sw(SW_MESSAGE_ADDRESS_TYPE_FAIL);
+    }
+
+    if (G_context.msg_info.address_type != 0 && G_context.msg_info.address_type != 1) {
+        return io_send_sw(SW_MESSAGE_ADDRESS_TYPE_FAIL);
     }
 
     if (!buffer_read_u32(cdata, &G_context.msg_info.address_index, BE)) {
-        return io_send_sw(SW_WRONG_DATA_LENGTH);
+        return io_send_sw(SW_MESSAGE_ADDRESS_TYPE_FAIL);
     }
 
     uint8_t message_len = 0;
     if (!buffer_read_u8(cdata, &message_len)) {
-        return io_send_sw(SW_WRONG_DATA_LENGTH);
+        return io_send_sw(SW_MESSAGE_LEN_PARSING_FAIL);
+    }
+
+    if (message_len == 0) {
+        return io_send_sw(SW_MESSAGE_TOO_SHORT);
     }
 
     if (message_len > MAX_MESSAGE_LEN) {
@@ -69,13 +77,13 @@ int handler_sign_msg(buffer_t *cdata) {
     G_context.msg_info.message_len = (size_t) message_len;
 
     if (!buffer_can_read(cdata, G_context.msg_info.message_len)) {
-        return io_send_sw(SW_WRONG_DATA_LENGTH);
+        return io_send_sw(SW_MESSAGE_PARSING_FAIL);
     }
 
     memcpy(G_context.msg_info.message, cdata->ptr + cdata->offset, G_context.msg_info.message_len);
 
     if (!buffer_seek_cur(cdata, G_context.msg_info.message_len)) {
-        return io_send_sw(SW_WRONG_DATA_LENGTH);
+        return io_send_sw(SW_MESSAGE_UNEXPECTED);
     }
 
     G_context.bip32_path[0] = 0x8000002C;
diff --git a/src/helper/send_response.h b/src/helper/send_response.h
index 49b9695..f15e6f3 100644
--- a/src/helper/send_response.h
+++ b/src/helper/send_response.h
@@ -24,8 +24,7 @@
 #pragma once
 
 #include "os.h"
-
-#include "../common/macros.h"
+#include "macros.h"
 
 /**
  * Length of public key.
diff --git a/src/sw.h b/src/sw.h
index 2f81e8a..a60be47 100644
--- a/src/sw.h
+++ b/src/sw.h
@@ -84,8 +84,14 @@
  */
 #define SW_SIGNATURE_FAIL 0xB008
 
-#define SW_WRONG_BIP32_PURPOSE   0xB009
-#define SW_WRONG_BIP32_COIN_TYPE 0xB00A
-#define SW_WRONG_BIP32_TYPE      0xB00B
-#define SW_WRONG_BIP32_PATH_LEN  0xB00C
-#define SW_MESSAGE_TOO_LONG      0xB00D
+#define SW_WRONG_BIP32_PURPOSE        0xB009
+#define SW_WRONG_BIP32_COIN_TYPE      0xB00A
+#define SW_WRONG_BIP32_TYPE           0xB00B
+#define SW_WRONG_BIP32_PATH_LEN       0xB00C
+#define SW_MESSAGE_PARSING_FAIL       0xB010
+#define SW_MESSAGE_TOO_LONG           0xB011
+#define SW_MESSAGE_TOO_SHORT          0xB012
+#define SW_MESSAGE_ADDRESS_TYPE_FAIL  0xB013
+#define SW_MESSAGE_ADDRESS_INDEX_FAIL 0xB014
+#define SW_MESSAGE_LEN_PARSING_FAIL   0xB015
+#define SW_MESSAGE_UNEXPECTED         0xB016
diff --git a/src/ui/bagl_display.c b/src/ui/bagl_display.c
index 6e55f66..30b58e7 100644
--- a/src/ui/bagl_display.c
+++ b/src/ui/bagl_display.c
@@ -44,7 +44,8 @@
 #include "../transaction/types.h"
 #include "../transaction/utils.h"
 #include "bip32.h"
-#include "../common/format.h"
+#include "../common/format_local.h"
+#include "format.h"
 #include "../menu.h"
 
 static action_validate_cb g_validate_callback;
@@ -229,7 +230,7 @@ int ui_display_transaction() {
 }
 
 // Step with icon and text
-UX_STEP_NOCB(ux_display_confirm_message_step, pn, {&C_icon_eye, "Confirm Message"});
+UX_STEP_NOCB(ux_display_confirm_message_step, pn, {&C_icon_eye, "Review Message"});
 
 // Step with title/text for message
 UX_STEP_NOCB(ux_display_message_step,
@@ -267,11 +268,11 @@ int ui_display_message() {
     }
 
     memset(g_message, 0, sizeof(g_message));
-    snprintf(g_message,
-             sizeof(g_message),
-             "%.*s",
-             G_context.msg_info.message_len,
-             G_context.msg_info.message);
+
+    format_message_to_sign(g_message,
+                           (int) sizeof(g_message),
+                           (char *) G_context.msg_info.message,
+                           (int) G_context.msg_info.message_len);
 
     g_validate_callback = &ui_action_validate_message;
 
diff --git a/src/ui/nbgl_display_address.c b/src/ui/nbgl_display_address.c
index 112bb8f..351f8c8 100644
--- a/src/ui/nbgl_display_address.c
+++ b/src/ui/nbgl_display_address.c
@@ -43,7 +43,7 @@
 #include "../types.h"
 #include "../transaction/types.h"
 #include "bip32.h"
-#include "../common/format.h"
+#include "format.h"
 #include "../menu.h"
 
 static char g_address[43];
diff --git a/src/ui/nbgl_display_message.c b/src/ui/nbgl_display_message.c
index dee6e2e..40e8093 100644
--- a/src/ui/nbgl_display_message.c
+++ b/src/ui/nbgl_display_message.c
@@ -43,7 +43,8 @@
 #include "../types.h"
 #include "../transaction/types.h"
 #include "bip32.h"
-#include "../common/format.h"
+#include "../common/format_local.h"
+#include "format.h"
 #include "../menu.h"
 
 static char g_message[MAX_MESSAGE_LEN];
@@ -59,6 +60,15 @@ static void confirm_message_rejection(void) {
     nbgl_useCaseStatus("Message signing\ncancelled", false, ui_menu_main);
 }
 
+static void ask_message_rejection_confirmation(void) {
+    // display a choice to confirm/cancel rejection
+    nbgl_useCaseConfirm("Reject message?",
+                        NULL,
+                        "Yes, Reject",
+                        "Go back to message",
+                        confirm_message_rejection);
+}
+
 static void confirm_message_approval(void) {
     // display a success status page and go back to main
     validate_message(true);
@@ -69,7 +79,7 @@ static void review_message_choice(bool confirm) {
     if (confirm) {
         confirm_message_approval();
     } else {
-        confirm_message_rejection();
+        ask_message_rejection_confirmation();
     }
 }
 
@@ -108,18 +118,17 @@ int ui_display_message() {
     }
 
     memset(g_message, 0, sizeof(g_message));
-    snprintf(g_message,
-             sizeof(g_message),
-             "%.*s",
-             G_context.msg_info.message_len,
-             G_context.msg_info.message);
+    format_message_to_sign(g_message,
+                           sizeof(g_message),
+                           (char *) G_context.msg_info.message,
+                           G_context.msg_info.message_len);
 
     nbgl_useCaseReviewStart(&C_stax_app_kaspa_64px,
                             "Sign Message",
                             NULL,
-                            "Cancel",
+                            "Reject message",
                             continue_message_review,
-                            confirm_message_rejection);
+                            ask_message_rejection_confirmation);
     return 0;
 }
 
diff --git a/src/ui/nbgl_display_transaction.c b/src/ui/nbgl_display_transaction.c
index 103626e..90c3297 100755
--- a/src/ui/nbgl_display_transaction.c
+++ b/src/ui/nbgl_display_transaction.c
@@ -44,7 +44,7 @@
 #include "../transaction/types.h"
 #include "../transaction/utils.h"
 #include "bip32.h"
-#include "../common/format.h"
+#include "format.h"
 #include "../menu.h"
 
 // Buffer where the transaction amount string is written
diff --git a/tests/application_client/kaspa_command_sender.py b/tests/application_client/kaspa_command_sender.py
index 74b4530..e5af126 100644
--- a/tests/application_client/kaspa_command_sender.py
+++ b/tests/application_client/kaspa_command_sender.py
@@ -38,25 +38,31 @@ class InsType(IntEnum):
     SIGN_MESSAGE   = 0x07
 
 class Errors(IntEnum):
-    SW_DENY                    = 0x6985
-    SW_WRONG_P1P2              = 0x6A86
-    SW_WRONG_DATA_LENGTH       = 0x6A87
-    SW_INS_NOT_SUPPORTED       = 0x6D00
-    SW_CLA_NOT_SUPPORTED       = 0x6E00
-    SW_WRONG_RESPONSE_LENGTH   = 0xB000
-    SW_DISPLAY_BIP32_PATH_FAIL = 0xB001
-    SW_DISPLAY_ADDRESS_FAIL    = 0xB002
-    SW_DISPLAY_AMOUNT_FAIL     = 0xB003
-    SW_WRONG_TX_LENGTH         = 0xB004
-    SW_TX_PARSING_FAIL         = 0xB005
-    SW_TX_HASH_FAIL            = 0xB006
-    SW_BAD_STATE               = 0xB007
-    SW_SIGNATURE_FAIL          = 0xB008
-    SW_WRONG_BIP32_PURPOSE     = 0xB009
-    SW_WRONG_BIP32_COIN_TYPE   = 0xB00A
-    SW_WRONG_BIP32_TYPE        = 0xB00B
-    SW_WRONG_BIP32_PATH_LEN    = 0xB00C
-    SW_MESSAGE_TOO_LONG        = 0xB00D
+    SW_DENY                       = 0x6985
+    SW_WRONG_P1P2                 = 0x6A86
+    SW_WRONG_DATA_LENGTH          = 0x6A87
+    SW_INS_NOT_SUPPORTED          = 0x6D00
+    SW_CLA_NOT_SUPPORTED          = 0x6E00
+    SW_WRONG_RESPONSE_LENGTH      = 0xB000
+    SW_DISPLAY_BIP32_PATH_FAIL    = 0xB001
+    SW_DISPLAY_ADDRESS_FAIL       = 0xB002
+    SW_DISPLAY_AMOUNT_FAIL        = 0xB003
+    SW_WRONG_TX_LENGTH            = 0xB004
+    SW_TX_PARSING_FAIL            = 0xB005
+    SW_TX_HASH_FAIL               = 0xB006
+    SW_BAD_STATE                  = 0xB007
+    SW_SIGNATURE_FAIL             = 0xB008
+    SW_WRONG_BIP32_PURPOSE        = 0xB009
+    SW_WRONG_BIP32_COIN_TYPE      = 0xB00A
+    SW_WRONG_BIP32_TYPE           = 0xB00B
+    SW_WRONG_BIP32_PATH_LEN       = 0xB00C
+    SW_MESSAGE_PARSING_FAIL       = 0xB010
+    SW_MESSAGE_TOO_LONG           = 0xB011
+    SW_MESSAGE_TOO_SHORT          = 0xB012
+    SW_MESSAGE_ADDRESS_TYPE_FAIL  = 0xB013
+    SW_MESSAGE_ADDRESS_INDEX_FAIL = 0xB014
+    SW_MESSAGE_LEN_PARSING_FAIL   = 0xB015
+    SW_MESSAGE_UNEXPECTED         = 0xB016
 
 def split_message(message: bytes, max_size: int) -> List[bytes]:
     return [message[x:x + max_size] for x in range(0, len(message), max_size)]
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diff --git a/tests/snapshots/stax/test_sign_message_simple/00000.png b/tests/snapshots/stax/test_sign_message_simple/00000.png
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diff --git a/tests/test_sign_personal_message_cmd.py b/tests/test_sign_personal_message_cmd.py
index 34b53fd..7812b57 100644
--- a/tests/test_sign_personal_message_cmd.py
+++ b/tests/test_sign_personal_message_cmd.py
@@ -108,4 +108,37 @@ def test_sign_message_too_long(firmware, backend, navigator, test_name):
     last_response = client.send_raw_apdu(InsType.SIGN_MESSAGE, p1=P1.P1_INPUTS, p2=P2.P2_LAST, data=message_data.serialize())
 
     assert last_response.status == Errors.SW_MESSAGE_TOO_LONG
-    
\ No newline at end of file
+
+def test_sign_message_refused(firmware, backend, navigator, test_name):
+    # Use the app interface instead of raw interface
+    client = KaspaCommandSender(backend)
+
+    address_type = 1
+    address_index = 6
+    message = "Hello Kaspa!"
+
+    message_data = PersonalMessage(address_type, address_index, message)
+
+    if firmware.device.startswith("nano"):
+        with client.sign_message(message_data=message_data):
+            # Disable raising when trying to unpack an error APDU
+            backend.raise_policy = RaisePolicy.RAISE_NOTHING
+            navigator.navigate_until_text_and_compare(NavInsID.RIGHT_CLICK,
+                                                      [NavInsID.BOTH_CLICK],
+                                                      "Reject",
+                                                      ROOT_SCREENSHOT_PATH,
+                                                      test_name)
+
+        assert client.get_async_response().status == Errors.SW_DENY
+    else:
+        for i in range(3):
+            instructions = [NavInsID.USE_CASE_REVIEW_TAP] * i
+            instructions += [NavInsID.USE_CASE_REVIEW_REJECT,
+                             NavInsID.USE_CASE_CHOICE_CONFIRM,
+                             NavInsID.USE_CASE_STATUS_DISMISS]
+            with client.sign_message(message_data=message_data):
+                backend.raise_policy = RaisePolicy.RAISE_NOTHING
+                navigator.navigate_and_compare(ROOT_SCREENSHOT_PATH,
+                                               test_name + f"/part{i}",
+                                               instructions)
+            assert client.get_async_response().status == Errors.SW_DENY
\ No newline at end of file
diff --git a/unit-tests/CMakeLists.txt b/unit-tests/CMakeLists.txt
index 0842ec4..10fade0 100644
--- a/unit-tests/CMakeLists.txt
+++ b/unit-tests/CMakeLists.txt
@@ -61,7 +61,7 @@ add_library(read SHARED /opt/ledger-secure-sdk/lib_standard_app/read.c)
 add_library(sighash SHARED ../src/sighash.c)
 add_library(personal_message SHARED ../src/personal_message.c)
 add_library(write SHARED /opt/ledger-secure-sdk/lib_standard_app/write.c)
-add_library(format SHARED ../src/common/format.c)
+add_library(format_local SHARED ../src/common/format_local.c)
 add_library(apdu_parser SHARED ../src/apdu/parser.c)
 add_library(transaction_deserialize ../src/transaction/deserialize.c)
 add_library(transaction_serialize ../src/transaction/serialize.c)
@@ -69,7 +69,7 @@ add_library(transaction_utils ../src/transaction/utils.c)
 add_library(varint SHARED /opt/ledger-secure-sdk/lib_standard_app/varint.c)
 
 target_link_libraries(test_address PUBLIC cmocka gcov address cashaddr)
-target_link_libraries(test_format PUBLIC cmocka gcov format)
+target_link_libraries(test_format PUBLIC cmocka gcov format_local)
 target_link_libraries(test_sighash PUBLIC cmocka gcov sighash blake2b write)
 target_link_libraries(test_personal_message PUBLIC cmocka gcov personal_message blake2b write)
 target_link_libraries(test_apdu_parser PUBLIC cmocka gcov apdu_parser)
diff --git a/unit-tests/test_format.c b/unit-tests/test_format.c
index 06a1396..e3c2e28 100644
--- a/unit-tests/test_format.c
+++ b/unit-tests/test_format.c
@@ -30,109 +30,21 @@
 
 #include <cmocka.h>
 
-#include "common/format.h"
+#include "common/format_local.h"
 
-static void test_format_i64(void **state) {
+static void test_format_message_to_sign_simple(void **state) {
     (void) state;
 
-    char temp[22] = {0};
+    char message[] = "Hello Kaspa!";
+    char dest[12] = {0};
 
-    int64_t value = 0;
-    assert_true(format_i64(temp, sizeof(temp), value));
-    assert_string_equal(temp, "0");
+    format_message_to_sign(dest, (int) sizeof(dest), message, (int) sizeof(message));
 
-    value = (int64_t) 9223372036854775807ull;  // MAX_INT64
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_i64(temp, sizeof(temp), value));
-    assert_string_equal(temp, "9223372036854775807");
-
-    // buffer too small
-    assert_false(format_i64(temp, sizeof(temp) - 5, value));
-
-    value = (int64_t) -9223372036854775808ull;  // MIN_INT64
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_i64(temp, sizeof(temp), value));
-    assert_string_equal(temp, "-9223372036854775808");
-}
-
-static void test_format_u64(void **state) {
-    (void) state;
-
-    char temp[21] = {0};
-
-    uint64_t value = 0;
-    assert_true(format_u64(temp, sizeof(temp), value));
-    assert_string_equal(temp, "0");
-
-    value = (uint64_t) 18446744073709551615ull;  // MAX_UNT64
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_u64(temp, sizeof(temp), value));
-    assert_string_equal(temp, "18446744073709551615");
-
-    // buffer too small
-    assert_false(format_u64(temp, sizeof(temp) - 5, value));
-}
-
-static void test_format_fpu64_trimmed(void **state) {
-    (void) state;
-
-    char temp[22] = {0};
-
-    uint64_t amount = 0ull;  // satoshi
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_fpu64_trimmed(temp, sizeof(temp), amount, 8));
-    assert_string_equal(temp, "0");  // BTC
-
-    amount = 100000000ull;  // satoshi
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_fpu64_trimmed(temp, sizeof(temp), amount, 8));
-    assert_string_equal(temp, "1");  // BTC
-
-    amount = 24964823ull;  // satoshi
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_fpu64_trimmed(temp, sizeof(temp), amount, 8));
-    assert_string_equal(temp, "0.24964823");  // BTC
-
-    amount = 100ull;  // satoshi
-    memset(temp, 0, sizeof(temp));
-    assert_true(format_fpu64_trimmed(temp, sizeof(temp), amount, 8));
-    assert_string_equal(temp, "0.000001");  // BTC
-    // buffer too small
-    assert_false(format_fpu64_trimmed(temp, sizeof(temp) - 16, amount, 8));
-
-    char temp2[50] = {0};
-
-    amount = 1000000000000000000ull;  // wei
-    assert_true(format_fpu64_trimmed(temp2, sizeof(temp2), amount, 18));
-    assert_string_equal(temp2, "1");  // ETH
-
-    amount = 100000000000000000ull;  // wei
-    assert_true(format_fpu64_trimmed(temp2, sizeof(temp2), amount, 18));
-    assert_string_equal(temp2, "0.1");  // ETH
-
-    // buffer too small
-    amount = 1000000000000000001ull;  // wei
-    assert_false(format_fpu64_trimmed(temp2, sizeof(temp2) - 20, amount, 18));
-}
-
-static void test_format_hex(void **state) {
-    (void) state;
-
-    uint8_t address[] = {0xde, 0xb,  0x29, 0x56, 0x69, 0xa9, 0xfd, 0x93, 0xd5, 0xf2,
-                         0x8d, 0x9e, 0xc8, 0x5e, 0x40, 0xf4, 0xcb, 0x69, 0x7b, 0xae};
-    char output[2 * sizeof(address) + 1] = {0};
-
-    assert_int_equal(2 * sizeof(address) + 1,
-                     format_hex(address, sizeof(address), output, sizeof(output)));
-    assert_string_equal(output, "DE0B295669A9FD93D5F28D9EC85E40F4CB697BAE");
-    assert_int_equal(-1, format_hex(address, sizeof(address), output, sizeof(address)));
+    assert_string_equal(dest, "Hello Kaspa!");
 }
 
 int main() {
-    const struct CMUnitTest tests[] = {cmocka_unit_test(test_format_i64),
-                                       cmocka_unit_test(test_format_u64),
-                                       cmocka_unit_test(test_format_fpu64_trimmed),
-                                       cmocka_unit_test(test_format_hex)};
+    const struct CMUnitTest tests[] = {cmocka_unit_test(test_format_message_to_sign_simple)};
 
     return cmocka_run_group_tests(tests, NULL, NULL);
 }