From 2672a46218139fc5cbb4844096da451f7e243849 Mon Sep 17 00:00:00 2001
From: Benedict <benedict@0xb8000.de>
Date: Tue, 1 Mar 2016 21:56:15 +0100
Subject: set 1, challenge 3 completed

---
 task1_hex_to_base64.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 5 deletions(-)

(limited to 'task1_hex_to_base64.c')

diff --git a/task1_hex_to_base64.c b/task1_hex_to_base64.c
index 9871055..40c0a94 100644
--- a/task1_hex_to_base64.c
+++ b/task1_hex_to_base64.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <ctype.h>
 
 static const unsigned char base64_encode[] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
@@ -135,7 +136,7 @@ void two_char_hex(char *start, char *result)
 	*result = *result | second;
 }
 
-int convert_hex_string_to_binary(char *encode, char* result)
+int convert_hex_string_to_character_string(char *encode, char* result)
 {
 	int i;
 	int length = strlen(encode);
@@ -177,6 +178,19 @@ void xor_string(char *str1, char* str2, char *result, int length) {
 	return;
 		
 }
+
+
+void xor_string_single_byte(char byte, char* string, char *result, int length) {
+	int i;
+
+	for(i=0;i<length;i++)
+		result[i] = string[i] ^ byte;
+
+	result[i] = '\0';
+
+	return;
+}
+
 /**
  * results must be to times bigger than str1
  */
@@ -196,6 +210,25 @@ void hex_binary_to_string(char *str1, char *result, int length)
 	result[i*2] = '\0';
 }
 
+
+
+int score_based_on_frequent_characters(char *string)
+{
+	int number = 0;
+	int i;
+	int length = strlen(string);
+	char tmp;
+
+	for(i=0;i<strlen(string);i++) {
+		tmp = tolower(string[i]);	
+		if( tmp == 'e' || tmp == 'a' || tmp == 'i' || tmp == 'o'
+			|| tmp == 'u' )
+			number++;
+	}
+
+	return (number*100/length);
+}
+
 int main(int argc, char **argv)
 {
 	if (argc == 3 ) {
@@ -205,25 +238,39 @@ int main(int argc, char **argv)
 		char *base64= malloc(length);
 		char *__xor_string = malloc(length);
 		char *back_hex = malloc(length);
-		int i = convert_hex_string_to_binary(argv[1], tmp);
-		int j = convert_hex_string_to_binary(argv[2], tmp2);
+		int i = convert_hex_string_to_character_string(argv[1], tmp);
+		int j = convert_hex_string_to_character_string(argv[2], tmp2);
 		xor_string(tmp, tmp2, __xor_string, strlen(argv[2]));
 		// convert the __xor_string to printable charaters
 		hex_binary_to_string(tmp2, back_hex, strlen(argv[2]));
+		printf("***************************\n");
+		printf("set 1, challelnge 1:\n");
 		printf("input string 1:\n");
 		printf("%s\n", argv[1]);
 		printf("input string 2:\n");
 		printf("%s\n", argv[2]);
-		/*
+
 		printf("char string of arg 1:\n");
 		printf("%s\n", tmp);
 		printf("char string of arg 2:\n");
 		printf("%s\n", tmp2);
-		*/
+
 		printf("string 2 from hex back to printable charaters:\n");	
 		printf("%s\n", back_hex);
+		printf("***************************\n");
+		printf("set 1, challenge 2\n");
 		printf("xor string:\n");
 		hex_binary_to_string(__xor_string, back_hex, strlen(argv[2]));
 		printf("%s\n", back_hex);
+
+		printf("***************************\n");
+		printf("set 1, challenge 3\n");
+		for(i= 'A'; i< 'Z'; i++) {
+			xor_string_single_byte((char) i, tmp2, __xor_string, j);
+			int score = score_based_on_frequent_characters(__xor_string);
+			if(score > 30)
+				printf("char: %c, score: %i, string: %s\n", (char) i, score, __xor_string);
+		}
+
 	}
 }
-- 
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