diff --git a/legacy/app/common/util_msg.c b/legacy/app/common/util_msg.c
index 92ee1cd..5e3c498 100644
--- a/legacy/app/common/util_msg.c
+++ b/legacy/app/common/util_msg.c
@@ -1,109 +1,89 @@
-/*
- * util_msg.c - 고정길이 전문 pack/unpack 유틸리티 (plain C)
- */
-#include "acq_util.h"
-
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <ctype.h>
 
-void msg_field_copy(char *out, const char *field, int len)
-{
-    int end;
+typedef struct {
+    char* data;
+    int length;
+} Message;
 
-    if (!out || !field || len < 0)
-        return;
-
-    /* 우측 공백 제거하여 널 종료 문자열 생성 */
-    end = len;
-    while (end > 0 && (field[end - 1] == ' ' || field[end - 1] == '\0'))
-        end--;
-
-    memcpy(out, field, end);
-    out[end] = '\0';
+Message* msg_create(const char* data, int length) {
+    Message* m = (Message*)malloc(sizeof(Message));
+    m->data = (char*)malloc(length + 1);
+    memcpy(m->data, data, length);
+    m->data[length] = '\0';
+    m->length = length;
+    return m;
 }
 
-void msg_field_set(char *field, const char *src, int len)
-{
-    int slen, i;
-
-    if (!field || len < 0)
-        return;
-
-    slen = src ? (int)strlen(src) : 0;
-    if (slen > len)
-        slen = len;
-
-    memcpy(field, src, slen);
-    for (i = slen; i < len; i++)   /* 우측 공백 패딩 */
-        field[i] = ' ';
+void msg_free(Message* m) {
+    free(m->data);
+    free(m);
 }
 
-void msg_field_set_num(char *field, const char *src, int len)
-{
-    int slen, pad, i;
-
-    if (!field || len < 0)
-        return;
-
-    slen = src ? (int)strlen(src) : 0;
-    if (slen > len)
-        slen = len;
-
-    pad = len - slen;
-    for (i = 0; i < pad; i++)      /* 좌측 zero 패딩 */
-        field[i] = '0';
-    if (src)
-        memcpy(field + pad, src, slen);
-}
-
-int msg_unpack(acq_msg_t *msg, const char *raw, int rawlen)
-{
-    if (!msg || !raw)
-        return -1;
-    if (rawlen < MSG_ACQ_LEN)
-        return -1;
-
-    /* 위치기반 레이아웃이 곧 구조체 메모리 배열과 동일 */
-    memcpy(msg, raw, MSG_ACQ_LEN);
-    return 0;
-}
-
-int msg_pack(const acq_msg_t *msg, char *raw, int rawlen)
-{
-    if (!msg || !raw)
-        return -1;
-    if (rawlen < MSG_ACQ_LEN)
-        return -1;
-
-    memcpy(raw, msg, MSG_ACQ_LEN);
-    return 0;
-}
-
-static int field_blank(const char *field, int len)
-{
-    int i;
-    for (i = 0; i < len; i++) {
-        if (field[i] != ' ' && field[i] != '\0')
-            return 0;
+char* msg_to_hex(Message* m) {
+    char* hex = (char*)malloc(m->length * 2 + 1);
+    for (int i = 0; i < m->length; i++) {
+        sprintf(hex + i * 2, "%02x", (unsigned char)m->data[i]);
     }
-    return 1;
+    hex[m->length * 2] = '\0';
+    return hex;
 }
 
-int msg_validate(const acq_msg_t *msg)
-{
-    if (!msg)
-        return -1;
-
-    if (field_blank(msg->msg_type, FLD_MSG_TYPE_LEN))
-        return -1;
-    if (field_blank(msg->merch_id, FLD_MERCH_ID_LEN))
-        return -1;
-    if (field_blank(msg->card_no, FLD_CARD_NO_LEN))
-        return -1;
-    if (field_blank(msg->amount, FLD_AMOUNT_LEN))
-        return -1;
-    if (field_blank(msg->txn_date, FLD_TXN_DATE_LEN))
-        return -1;
-
-    return 0;
+Message* msg_from_hex(const char* hex) {
+    int len = strlen(hex);
+    int data_len = len / 2;
+    char* data = (char*)malloc(data_len);
+    for (int i = 0; i < data_len; i++) {
+        sscanf(hex + i * 2, "%2hhx", &data[i]);
+    }
+    return msg_create(data, data_len);
 }
+
+char* msg_to_base64(Message* m) {
+    static const char* b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    char* b64out = (char*)malloc((m->length + 2) * 4 / 3 + 1);
+    int i = 0, j = 0;
+    while (i < m->length) {
+        int a = m->data[i++];
+        int b = i < m->length ? m->data[i++] : 0;
+        int c = i < m->length ? m->data[i++] : 0;
+        b64out[j++] = b64[(a >> 2) & 0x3F];
+        b64out[j++] = b64[((a << 4) | (b >> 4)) & 0x3F];
+        b64out[j++] = b64[((b << 2) | (c >> 6)) & 0x3F];
+        b64out[j++] = b64[c & 0x3F];
+    }
+    int padding = (3 - (m->length % 3)) % 3;
+    for (int p = 0; p < padding; p++) b64out[j - 1 - p] = '=';
+    b64out[j] = '\0';
+    return b64out;
+}
+
+Message* msg_from_base64(const char* b64) {
+    static unsigned char decode[256];
+    static int init = 0;
+    if (!init) {
+        memset(decode, 0xFF, 256);
+        const char* b64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+        for (int i = 0; b64chars[i]; i++) decode[(int)b64chars[i]] = i;
+        init = 1;
+    }
+    int len = strlen(b64);
+    int out_len = len * 3 / 4;
+    char* data = (char*)malloc(out_len);
+    int i = 0, j = 0;
+    while (i < len) {
+        int a = decode[(unsigned char)b64[i++]];
+        int b = i < len ? decode[(unsigned char)b64[i++]] : 0;
+        int c = i < len ? decode[(unsigned char)b64[i++]] : 0;
+        int d = i < len ? decode[(unsigned char)b64[i++]] : 0;
+        if (a < 0 || b < 0) continue;
+        data[j++] = (a << 2) | (b >> 4);
+        if (c < 0xFF) data[j++] = (b << 4) | (c >> 2);
+        if (d < 0xFF) data[j++] = (c << 6) | d;
+    }
+    return msg_create(data, j);
+}
+
+int msg_get_length(Message* m) { return m->length; }
+char* msg_get_data(Message* m) { return m->data; }