diff --git a/include/mango/util.h b/include/mango/util.h
index bf8bd4e..89cfb8c 100644
--- a/include/mango/util.h
+++ b/include/mango/util.h
@@ -53,6 +53,8 @@ extern uint64_t host_to_little_u64(uint64_t v);
 extern uint64_t big_to_host_u64(uint64_t v);
 extern uint64_t little_to_host_u64(uint64_t v);
 
+extern bool fill_random(void *buffer, unsigned int size);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/include/mango/libc/ctype.h b/libc/include/mango/libc/ctype.h
index 27b04b9..4dc2eef 100644
--- a/libc/include/mango/libc/ctype.h
+++ b/libc/include/mango/libc/ctype.h
@@ -18,7 +18,6 @@ extern int isupper(int c);
 extern int isxdigit(int c);
 extern int tolower(int c);
 extern int toupper(int c);
-extern int fill_random(unsigned char *buffer, unsigned int size);
 
 #ifdef __cplusplus
 }
diff --git a/util/random.c b/util/random.c
new file mode 100644
index 0000000..eb7243c
--- /dev/null
+++ b/util/random.c
@@ -0,0 +1,36 @@
+#include <mango/util.h>
+
+static unsigned int random_seed = 53455346;
+
+bool fill_random(void *p, unsigned int size)
+{
+	unsigned char *buffer = p;
+
+	if (!buffer || !size) {
+		return false;
+	}
+
+	for (uint32_t i = 0; i < size; i++) {
+		uint32_t next = random_seed;
+		uint32_t result;
+
+		next *= 1103515245;
+		next += 12345;
+		result = (uint32_t)(next / 65536) % 2048;
+
+		next *= 1103515245;
+		next += 12345;
+		result <<= 10;
+		result ^= (uint32_t)(next / 65536) % 1024;
+
+		next *= 1103515245;
+		next += 12345;
+		result <<= 10;
+		result ^= (uint32_t)(next / 65536) % 1024;
+		random_seed = next;
+
+		buffer[i] = (uint8_t)(result % 256);
+	}
+
+	return true;
+}