diff --git a/client/src/util.c b/client/src/util.c
index 723f3e758..51408a524 100644
--- a/client/src/util.c
+++ b/client/src/util.c
@@ -911,27 +911,32 @@ https://github.com/ApertureLabsLtd/RFIDler/blob/master/firmware/Pic32/RFIDler.X/
 // convert hex to sequence of 0/1 bit values
 // returns number of bits converted
 int hextobinarray(char *target, char *source) {
-    int length, i, count = 0;
+    return hextobinarray_n(target, source, strlen(source));
+}
+
+int hextobinarray_n(char *target, char *source, int sourcelen) {
+    int i, count = 0;
     char *start = source;
-    length = strlen(source);
     // process 4 bits (1 hex digit) at a time
-    while (length--) {
+    while (sourcelen--) {
         char x = *(source++);
         // capitalize
-        if (x >= 'a' && x <= 'f')
+        if (x >= 'a' && x <= 'f') {
             x -= 32;
+        }
         // convert to numeric value
-        if (x >= '0' && x <= '9')
+        if (x >= '0' && x <= '9') {
             x -= '0';
-        else if (x >= 'A' && x <= 'F')
+        } else if (x >= 'A' && x <= 'F') {
             x -= 'A' - 10;
-        else {
+        } else {
             PrintAndLogEx(INFO, "(hextobinarray) discovered unknown character %c %d at idx %d of %s", x, x, (int16_t)(source - start), start);
             return 0;
         }
         // output
-        for (i = 0 ; i < 4 ; ++i, ++count)
+        for (i = 0 ; i < 4 ; ++i, ++count) {
             *(target++) = (x >> (3 - i)) & 1;
+        }
     }
 
     return count;
@@ -939,9 +944,14 @@ int hextobinarray(char *target, char *source) {
 
 // convert hex to human readable binary string
 int hextobinstring(char *target, char *source) {
-    int length = hextobinarray(target, source);
-    if (length == 0)
+    return hextobinstring_n(target, source, strlen(source));
+}
+
+int hextobinstring_n(char *target, char *source, int sourcelen) {
+    int length = hextobinarray_n(target, source, sourcelen);
+    if (length == 0) {
         return 0;
+    }
     binarraytobinstring(target, target, length);
     return length;
 }
diff --git a/client/src/util.h b/client/src/util.h
index c29fbd50f..4dab9ae06 100644
--- a/client/src/util.h
+++ b/client/src/util.h
@@ -112,7 +112,11 @@ int param_getbin_to_eol(const char *line, int paramnum, uint8_t *data, int maxda
 int param_getstr(const char *line, int paramnum, char *str, size_t buffersize);
 
 int hextobinarray(char *target, char *source);
+int hextobinarray_n(char *target, char *source, int sourcelen);
+
 int hextobinstring(char *target, char *source);
+int hextobinstring_n(char *target, char *source, int sourcelen);
+
 int binarraytohex(char *target, const size_t targetlen, const char *source, size_t srclen);
 void binarraytobinstring(char *target,  char *source, int length);
 int binstring2binarray(uint8_t *target, char *source, int length);