changement de nom & readme

CMakeLists.txt

@@ -1,8 +1,8 @@
 cmake_minimum_required(VERSION 3.17)
-project(lsd C)
+project(dip C)
 
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR})
 
-add_executable(lsd src/main.c src/lodepng.c src/hide.c src/extract.c src/utils.c)
+add_executable(dip src/main.c src/lodepng.c src/hide.c src/extract.c src/utils.c)
 include_directories(include)

bench.sh

@@ -1,12 +1,10 @@
 #!/bin/bash
 
-gcc src/* -I include -O2 -o lsd
-
 for ((i = 0; i < $1; i++)); do
   head -c 267K </dev/urandom >rdata
   original_hash=$(sha1sum rdata | cut -d " " -f 1)
-  ./lsd -h giedre.png rdata hdata.png
-  ./lsd -e hdata.png odata
+  ./dip -h giedre.png rdata hdata.png
+  ./dip -e hdata.png odata
   extracted_hash=$(sha1sum odata | cut -d " " -f 1)
   if [[ "$original_hash" == "$extracted_hash" ]]; then
     echo hash ok

readme.md

@@ -0,0 +1,93 @@
+# DIP - Data In Picture
+
+## A tool to hide binary stuff into PNG pictures using LSB
+
+### Presentation
+
+This tool allow to hide any type of file in a PNG pictures, provided that the following conditions are respected :
+
+- the picture is a 8-bits depth RGB PNG
+- the data is small enough to fit in the picture (maximum ~21 bits/pixel)
+
+The data will be hidden in the bits having the least importance in the picture in order to make the modification as
+imperceptible as possible.
+
+#### Details
+
+##### Header
+
+A header is embedded in the picture alongside the data. He is split in two main parts :
+
+- **LSB header *(3 bits)* :** hidden in the 3 last bits of the R component of the first pixel, it contains the number of
+  bits from the right reserved for the data in all the following components/pixels *(**L**east **S**ignificant **B**its)*. Its value is greater than 0 and lower than 8.
+
+- **Main header *(40 bits)* :**
+    - **Size header *(32 bits)* :** stored like regular data accordingly to the lsb value found in the first header.
+      Contains the size of the hidden data in bytes.
+    - **Reserved space *(8 bits)* :** useless for now. Maybe forever. Consider it a wasted byte.
+
+Reading this header needs to be done in two steps, as the first part is needed to retrieve the second one.
+
+#### Storage capacity
+
+For a picture of width `x` and height `y`, the maximum payload which can be hidden is given (in bits) by the formula
+
+```python
+21 * x * y - 47
+```
+
+This capacity is only reachable by pretty much destroying the original picture, only leaving it one out of 8 bits in
+each channel (the LSB value as described in the header section will be 7). If you're not into deepfry aesthetics, you
+will want to keep this value below 5. For a target maximum LSB of 4, the formula is
+
+```python
+12 * x * y - 44
+```
+
+Or, for a maximum LSB of v :
+
+```python
+(x * y * 3 - 1) * v - 40
+```
+
+Please note that theses formulas describes the way the program is supposed to act, but my incompetence and a certain lack of tests may lead its real behavior to slightly differ from this values.
+
+### Usage
+
+#### hiding
+
+```
+./dip -h <picture.png> <data> <output.png>
+```
+
+Hides `data` in `picture.png` and saves the resulting picture in `output.png`.
+
+#### extracting
+
+```
+./dip -e <picture.png> <output.data>
+```
+
+Extracts data hidden in `picture.png` and saves it in `output.data`. Using it on a picture which wasn't generated by DIP
+or has been altered is undefined behavior.
+
+#### cleaning
+
+```
+./dip -c <picture.png> <output.png>
+```
+
+Strips hidden data from `picture.png` and saves the resulting picture in `output.png`. Using it on a picture which
+wasn't generated by DIP or has been altered is undefined behavior.
+
+### Return Codes
+
+- **0 :** everything's fine
+- **1 :** small issue, like incorrect input
+- **2 :** the data doesn't fit in the picture
+- **3 :** a system call failed
+- **4 :** PNG loading/saving-related error
+
+### External libs
+
+PNG manipulation : [LodePNG by Lode Vandevenne](https://github.com/lvandeve/lodepng) ([zlib licensed](https://raw.githubusercontent.com/lvandeve/lodepng/master/LICENSE)).

src/extract.c

@@ -95,7 +95,7 @@ void get_info(byte *lsb, u32 *length, string picture_path) {
                 if (read_bytes < LEN_HEADER_SIZE) { // si on est en train de lire le header
                     real_length = (real_length << 8) | data;
                     if (read_bytes == 3) {
-                        *length = real_length + EMBEDDED_HEADER_SIZE;
+                        *length = real_length;
                         free(image);
                         return;
                     }

src/hide.c

@@ -1,4 +1,3 @@
-#include <time.h>
 #include "hide.h"
 
 void hide(string picture_path, string file_path, string output_path) {

src/main.c

@@ -53,7 +53,7 @@ int main(int argc, char *argv[]) {
         }
     }
 
-    printf("lsd - a tool to hide things in PNG pictures\nwritten by astequ\n\nUsage :\n\t- hiding     :"
+    printf("DIP - a tool to hide things in PNG pictures\nwritten by astequ\n\nUsage :\n\t- hiding     :"
            " %s -h <picture.png> <data> <output.png>\n\t- extracting : %s -e <picture.png> <output.data>\n\t- cleaning"
            "   : %s -c <picture.png> <output.png>\n", argv[0], argv[0], argv[0]);