From 4ed371cc378a3b579d46ed89a2677769a6d5ea24 Mon Sep 17 00:00:00 2001
From: Benedict <benedict@0xb8000.de>
Date: Tue, 22 Mar 2016 19:11:22 +0100
Subject: completed set 2 challenge 11

---
 set2/Makefile |  2 ++
 set2/task10.c |  4 ++-
 set2/task11.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+), 1 deletion(-)
 create mode 100644 set2/task11.c

(limited to 'set2')

diff --git a/set2/Makefile b/set2/Makefile
index 1f8f890..9c5f43e 100644
--- a/set2/Makefile
+++ b/set2/Makefile
@@ -9,6 +9,8 @@ task9:
 	$(CC) $(CFLAGS) task9.c $(LIB) $(CLIBS) -o task9
 task10:
 	$(CC) $(CFLAGS) task10.c $(LIB) $(CLIBS) -o task10
+task11:
+	$(CC) $(CFLAGS) task11.c $(LIB) $(CLIBS) -o task11
 task15:
 	$(CC) $(CFLAGS) task15.c $(LIB) $(CLIBS) -o task15
 clean:
diff --git a/set2/task10.c b/set2/task10.c
index fb8d0c1..19a7235 100644
--- a/set2/task10.c
+++ b/set2/task10.c
@@ -22,8 +22,10 @@ int main(int argc, char **argv)
 	decoded_content_length = decode_base64(file_content, decoded_content);
 	cleartext = malloc(decoded_content_length+1);
 	// aes cbc
-	aes_cbc(decoded_content, decoded_content_length, cleartext, string_key, iv);
+	aes_cbc(decoded_content, decoded_content_length, cleartext, string_key, iv, 0);
 	printf("%s\n", cleartext);
+
+
 	free(decoded_content);
 	free(cleartext);
 	return 0;
diff --git a/set2/task11.c b/set2/task11.c
new file mode 100644
index 0000000..60483e0
--- /dev/null
+++ b/set2/task11.c
@@ -0,0 +1,83 @@
+#include "../lib/lib2.h"
+#include "../lib/lib.h"
+
+int random_number_between(int min, int max)
+{
+	return (rand() % (max-min) + min);
+}
+
+
+int generate_random_bytes(char *buf, int length_key_bytes)
+{
+	int random_number;
+	int i;
+	for(i=0;i<length_key_bytes;i++) {
+		buf[i] = (char) random_number_between(0,255);
+	}
+
+}
+
+char *encrypt_with_random_bytes(char *toencrypt, int length, int ecb)
+{
+	int toappend_before = random_number_between(5,10);
+	int toappend_after= random_number_between(5,10);
+
+	char random_bytes[10];
+	char key[16];
+
+	char *result = malloc(length+toappend_before+toappend_after+1);
+	char *ciphertext = malloc(length+toappend_before+toappend_after+1);
+
+	generate_random_bytes(random_bytes, toappend_before);
+	
+	memcpy(result, random_bytes, toappend_before);
+	memcpy(&result[toappend_before], toencrypt, length);
+
+	generate_random_bytes(random_bytes, toappend_after);
+
+	memcpy(&result[length+toappend_before], random_bytes, toappend_after);
+	
+	generate_random_bytes(key, 16);
+
+
+	if(ecb)
+		aes_ecb(result, (length+toappend_before+toappend_after), ciphertext, key, 128, 1);
+	else {
+		char iv[16];
+		memset(iv, 0, 16);
+		aes_cbc(result, (length+toappend_before+toappend_after), ciphertext, key, iv, 1);
+	}
+
+	return ciphertext;
+}
+
+int main(int argc, char **argv)
+{
+	// set seed
+//	srand(1);
+	int i;
+	// encrypt ecb mode
+	char *cleartext = "Ok, dann mach ich mal einen richtigen Satz. Vielleicht ist das ECB mit so vielen gleichen Bloecken total ueberfordert. Oder der Satz muss einfach laenger sein. Man brauch also wirklich wohl erstmal ein bisschen Text, bevor man ECB erkennen kann";
+	char *ciphertext;
+	char *ciphertext_cbc;
+	char iv[16];
+
+	memset(iv, 0, 16);
+
+	ciphertext = encrypt_with_random_bytes(cleartext, strlen(cleartext), 1);
+	ciphertext_cbc = encrypt_with_random_bytes(cleartext, strlen(cleartext), 0);
+	//aes_ecb(cleartext, strlen(cleartext), ciphertext, "BUMMS", 128, 1);
+	//aes_cbc(cleartext, strlen(cleartext), ciphertext_cbc, "BUMMS", iv, 1);
+
+	if(string_is_ecb_encrypted(ciphertext_cbc, strlen(cleartext), 16))
+		printf("Das ist wohl ECB (ist es aber nicht!)\n");
+
+	if(string_is_ecb_encrypted(ciphertext, strlen(cleartext), 16))
+		printf("Das ist wohl ECB (richtig)\n");
+/*
+	for(i=0;i<strlen(cleartext);i++)
+		printf("%c", ciphertext_cbc[i]);
+	
+*/
+	return 0;
+}
-- 
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