diff --git a/includes/woody.h b/includes/woody.h
index a9005cc..c86a04a 100644
--- a/includes/woody.h
+++ b/includes/woody.h
@@ -17,7 +17,7 @@ typedef struct efl_content
 	long unsigned int file_size;
 	char	*file_path;
 	char	*file;
-
+	char	*extra_data;
 }				t_efl_content;
 
 
diff --git a/srcs/woody.c b/srcs/woody.c
index 57f8a3f..657fb30 100644
--- a/srcs/woody.c
+++ b/srcs/woody.c
@@ -1,12 +1,67 @@
 #include "../includes/woody.h"
 
+int elf_magic_numbers(char *str)
+{
+	return (!ft_strncmp(str, ELFMAG, SELFMAG));
+}
+
+size_t	find_stringtable_end(char *Sshstrtab) // not secure i think
+{
+	size_t strtab_index = 0;
+
+	while (Sshstrtab[strtab_index] != '\0' || Sshstrtab[strtab_index + 1] != '\0')
+	{
+		while (Sshstrtab[strtab_index] != '\0')
+			strtab_index++;
+		strtab_index++;
+	}
+	return strtab_index;
+}
+
+void	encrypt(char *start, unsigned long int size)
+{
+	size_t i = 0;
+
+	// while (i < size)
+	// {
+
+	// }
+	(void)i;
+	(void)start;
+	(void)size;
+}
+
 int woody(t_efl_content *file_content)
 {
 	Elf64_Ehdr *Ehdr = (Elf64_Ehdr *)secure_access(file_content->file, file_content->file_size, 0, sizeof(Elf64_Ehdr));
 
-	if (!Ehdr)
+	if (!Ehdr || !elf_magic_numbers(file_content->file) || Ehdr->e_ident[EI_CLASS] != 2)
+	{
+		ft_printf("Error: \'%s\' is not a valid 64-bit ELF file\n", file_content->file_path);
 		return EXIT_FAILURE;
+	}
+
+	Elf64_Shdr *Shdr = (Elf64_Shdr *)secure_access(file_content->file, file_content->file_size, Ehdr->e_shoff, sizeof(Elf64_Shdr));
+	if (Shdr == NULL || !secure_access(file_content->file, file_content->file_size, Ehdr->e_shoff, Ehdr->e_shnum * sizeof(Elf64_Shdr)))
+	{
+		return ft_put_error("Corrupted file");
+	}
+	if (file_content->file_size > Ehdr->e_shoff + Ehdr->e_shnum * sizeof(Elf64_Shdr))
+	{
+		printf("extra_data !\n"); // save it in file_content->extra_data and append it to the end of the woody file ? Could be dangerous
+	}
+
+	char *Sshstrtab = (char *)secure_access(file_content->file, file_content->file_size, Shdr[Ehdr->e_shstrndx].sh_offset, 0);
+	if (Sshstrtab == NULL)
+		return ft_put_error("Corrupted file");
+
+	size_t stringtable_end = find_stringtable_end(Sshstrtab);
 	
-	// if (Ehdr->e_ident[EI_CLASS])
+	if (Sshstrtab + stringtable_end > file_content->file + file_content->file_size)
+	{
+		return ft_put_error("Encrypt after the end of the file");
+	}
+	encrypt(Sshstrtab, stringtable_end);
+
 	return EXIT_SUCCESS;
 }
\ No newline at end of file