diff --git a/sha1.c b/sha1.c
index 29ee2ad..a6aacf7 100644
--- a/sha1.c
+++ b/sha1.c
@@ -1,3 +1,10 @@
+/**
+  * SHA1 - Secure Hash Algorithm 
+  * This code is a direct implementation of the algorithm presented in rfc3174.
+  * No optimizations has been used, although I tried to keep it small in order
+  * to fit on an ATTiny45 (together with VUSB).
+  * It is written in assumption that the target architecture is little endian.
+  */
 #include "sha1.h"
 
 #define H1 0x67452301
@@ -22,6 +29,7 @@ void sha1_addbyte(uint8_t c){
 	uint8_t* p=(uint8_t*)chunk;
 	uint8_t i=(chunk_cnt & 0x03);
 
+    /* chunk_cnt-i)+3-i deals with the endianess */
 	p[(chunk_cnt-i)+3-i]=c;
 	chunk_cnt++;
 	if(chunk_cnt==64){
@@ -76,9 +84,9 @@ void sha1_fill(int32_t len){
 	/*"append 0-bits to the message to obtain a length of len%512=448"*/
 	/*"append length of message in bits as 64-bit integer"*/
     uint8_t j;
-    uint8_t end=(uint8_t)((120-(len-(len/64)*64+1))%64+1);
+    uint8_t end=(uint8_t)((120-(len-(len/64)*64+1))%64);
     sha1_addbyte(0x80);
-	for(j=1;j<end;j++){
+	for(j=0;j<end;j++){
 		sha1_addbyte(0x00);
 	}
 	{
diff --git a/test.c b/test.c
index 01166fd..9f04214 100644
--- a/test.c
+++ b/test.c
@@ -8,7 +8,7 @@
 
 char sha1sum[41];
 
-#define SHA1STR() {                                               \
+#define SHA1STR() {                                             \
     p=sha1sum;                                                  \
     for(i=19; i>=0; --i){                                       \
         sprintf(p,"%02x", ((unsigned char*)(sha1_digest))[i] ); \
@@ -20,6 +20,9 @@ char sha1sum[41];
 #define SECRET1  {0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b}
 #define MSG1 "Hi There"
 
+#define SECRET2  {'J', 'e', 'f', 'e'};
+#define MSG2 ""
+
 int main(){
     /*SHA1STR makro needs those two*/
     int i;
@@ -49,10 +52,17 @@ int main(){
     printf("SHA1: %s\n",sha1sum);
     assert(strcmp("4d71043a68fa28b9592d1aa5748e5cd4291c0512",sha1sum)==0);   
 
-    char sec[20]=SECRET1;
+    char sec1[20]=SECRET1;
     hmac(MSG1,8,sec,20);
     SHA1STR();
     printf("HMAC: %s\n",sha1sum);
     assert(strcmp("b617318655057264e28bc0b6fb378c8ef146be00",sha1sum)==0);   
+
+    char sec1[20]=SECRET2;
+    hmac(MSG2,8,sec,20);
+    SHA1STR();
+    printf("HMAC: %s\n",sha1sum);
+    //assert(strcmp("b617318655057264e28bc0b6fb378c8ef146be00",sha1sum)==0);   
+
     
 }