From 3ba6d6ef2f481a17f750c164ebcc740514ee04cc Mon Sep 17 00:00:00 2001
From: schneider <schneider@blinkenlichts.net>
Date: Thu, 14 Jul 2011 02:16:57 +0200
Subject: [PATCH] added byte wise xxtea encryption up to 32bytes

---
 firmware/basic/xxtea.c | 86 +++++++++++++++++++++++++++++++++++++++++-
 firmware/basic/xxtea.h | 10 ++++-
 2 files changed, 92 insertions(+), 4 deletions(-)

diff --git a/firmware/basic/xxtea.c b/firmware/basic/xxtea.c
index 2e3da17..7da7a2e 100644
--- a/firmware/basic/xxtea.c
+++ b/firmware/basic/xxtea.c
@@ -12,8 +12,90 @@
 
 #define DELTA 0x9e3779b9
 #define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (k[(p&3)^e] ^ z)))
+#include "xxtea.h"
 
-void xxtea_encode(uint32_t *v, int n, uint32_t const k[4]) {
+uint32_t charp2uint32(uint8_t *data, uint8_t bytes)
+{
+    uint32_t r = 0;
+    if( bytes ){
+        r |= *data++;
+    }
+    if( bytes > 1){
+        r<<=8;
+        r |= *data++;
+    }
+    if( bytes > 2){
+        r<<=8;
+        r |= *data++;
+    }
+    if( bytes > 3){
+        r<<=8;
+        r |= *data++;
+    }
+    return r;
+}
+
+void charp2uint32p(uint8_t* data, uint8_t  n, uint32_t *v)
+{
+    int i,j=0;
+    int fullwords = n/4;
+    for(i=0; i<fullwords*4; i+=4){
+        v[j++] = charp2uint32(data+i,4);
+    }
+    
+    uint8_t extrabytes = n - i;
+    v[j] = charp2uint32(data+i,extrabytes);
+}
+
+void uint322charp(uint32_t data, uint8_t *buf, uint8_t bytes)
+{
+    if( bytes ){
+        buf[0] = data>>24;
+    if( bytes > 1)
+        buf[1] = (data>>16)&0xFF;
+    if( bytes > 2)
+        buf[2] = (data>>8)&0xFF;
+    if( bytes > 3)
+        buf[3] = (data>>0)&0xFF;
+}
+
+void uint32p2charp(uint8_t* data, uint8_t  n, uint32_t *v)
+{
+    int i;
+    int fullwords = n/4;
+    
+    for(i=0; i<fullwords; i++){
+        uint322charp(v[i],data+i*4,4);
+    }
+    
+    uint8_t extrabytes = n - fullwords*4;
+    uint322charp(v[i],data+i*4,extrabytes);
+}
+
+void xxtea_encode(uint8_t *data, int n, uint32_t const k[4])
+{
+    uint32_t v[8];      //maximum 32 bytes
+    int words = (n+3)/4;
+    if( words > 8 )
+        return;
+    charp2uint32p(data, n, v);
+    xxtea_encode_words(v, words, k);
+    uint32p2charp(data, n, v);
+}
+
+void xxtea_decode(uint8_t *data, int n, uint32_t const k[4])
+{
+    uint32_t v[8];      //maximum 32 bytes
+    int words = (n+3)/4;
+    if( words > 8 )
+        return;
+    charp2uint32p(data, n, v);
+    xxtea_decode_words(v, words, k);
+    uint32p2charp(data, n, v);
+}
+ 
+void xxtea_encode_words(uint32_t *v, int n, uint32_t const k[4])
+{
     uint32_t y, z, sum;
     unsigned p, rounds, e;
     rounds = 6 + 52/n;
@@ -31,7 +113,7 @@ void xxtea_encode(uint32_t *v, int n, uint32_t const k[4]) {
     } while (--rounds);
 }
 
-void xxtea_decode(uint32_t *v, int n, uint32_t const k[4]) {
+void xxtea_decode_words(uint32_t *v, int n, uint32_t const k[4]) {
     uint32_t y, z, sum;
     unsigned p, rounds, e;
 
diff --git a/firmware/basic/xxtea.h b/firmware/basic/xxtea.h
index 8cc7337..1718308 100644
--- a/firmware/basic/xxtea.h
+++ b/firmware/basic/xxtea.h
@@ -1,8 +1,14 @@
 #ifndef _XXTEA_H_
 #define _XXTEA_H_
 
-void xxtea_encode(uint32_t *v, int n, uint32_t const k[4]);
-void xxtea_decode(uint32_t *v, int n, uint32_t const k[4]);
+uint32_t charp2uint32(uint8_t *data, uint8_t bytes);
+void charp2uint32p(uint8_t* data, uint8_t  n, uint32_t *v);
+void uint322charp(uint32_t data, uint8_t *buf, uint8_t bytes);
+void uint32p2charp(uint8_t* data, uint8_t  n, uint32_t *v);
+void xxtea_encode(uint8_t *data, int n, uint32_t const k[4]);
+void xxtea_decode(uint8_t *v, int n, uint32_t const k[4]);
+void xxtea_encode_words(uint32_t *v, int n, uint32_t const k[4]);
+void xxtea_decode_words(uint32_t *v, int n, uint32_t const k[4]);
 
 #endif