diff --git a/solutions/c/crypto-square/1/crypto_square.c b/solutions/c/crypto-square/1/crypto_square.c
new file mode 100644
index 0000000..8f29f72
--- /dev/null
+++ b/solutions/c/crypto-square/1/crypto_square.c
@@ -0,0 +1,50 @@
+#include "crypto_square.h"
+#include <ctype.h>
+#include <math.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *ciphertext(const char *input){
+    if (!input) return NULL;
+
+    size_t len = strlen(input);
+    char *cleaned = malloc(len);
+    if (!cleaned) return NULL;
+
+    size_t count = 0;
+
+    {
+        size_t i = 0;
+        char c;
+        while ((c = input[i++])) if (isalpha(c)) cleaned[count++] = tolower(c); else if (isdigit(c)) cleaned[count++] = c; 
+    }
+
+    if (count == 0) {
+        free(cleaned);
+        return calloc(1, 1);
+    }
+
+    size_t c = ceil(sqrt(count));
+    size_t r = (c * (c - 1) >= count) ? c - 1 : c;
+
+    size_t size = c * r + (c - 1) + 1;
+    char *cipher = malloc(size);
+    if (!cipher) { free(cleaned); return NULL; }
+
+    memset(cipher, ' ', size);
+
+    size_t counter = 0;
+    for (size_t i = 0; i < c; i++) {
+        size_t old_counter = counter;
+        for (size_t j = i; j < count; j += c) {
+            cipher[counter++] = cleaned[j];
+        }
+        if (counter != old_counter + r) counter = old_counter + r;
+        if (i < c - 1) cipher[counter++] = ' ';
+    }
+
+    free(cleaned);
+    cipher[counter] = '\0';
+    return cipher;
+}
diff --git a/solutions/c/crypto-square/1/crypto_square.h b/solutions/c/crypto-square/1/crypto_square.h
new file mode 100644
index 0000000..b133e21
--- /dev/null
+++ b/solutions/c/crypto-square/1/crypto_square.h
@@ -0,0 +1,6 @@
+#ifndef CRYPTO_SQUARE_H
+#define CRYPTO_SQUARE_H
+
+char *ciphertext(const char *input);
+
+#endif