set2, completed 12 and 14

1 files changed, 45 insertions, 0 deletions

diff --git a/set2/task14.c b/set2/task14.c
new file mode 100644
index 0000000..586d174
--- /dev/null
+++ b/set2/task14.c
@@ -0,0 +1,45 @@
+#include "../lib/lib.h"
+#include "../lib/lib2.h"
+#include <time.h>
+
+/**
+ * This time there is a random amount of random data before our
+ * data. This is that annoys us. If we would one where our data
+ * would begin all would be fine, we would do the same as in task12
+ * But since we are using ECB blocks din't change with the random data.
+ * So we make a first request with our data empty and than make a second
+ * request with one byte. Than we compere the results. The blocks which 
+ * contain the random data keep the same, exceot the last, because we
+ * probably append our byte into that block instead of the first byte of
+ * our target string. Now we now how many blocks of random data are before 
+ * our data.
+ * To get the excat number of bytes, we add two blocksof A's. So one block is
+ * for sure filled just with A's. Than we remove A's until the block of A's
+ * change because our traget data get into it. Then blocksize-Removed A's
+ * is the offset block where our data start.
+ *	16*unchanged_blocks + BLOKCSIZE-RemovedA's
+ *
+ *
+**/
+#define BLOCKSIZE 16
+int main(int argc, char **argv)
+{
+	srand(time(NULL));
+	generate_random_bytes(key, 16);
+	// cleartext + maybe an additional block
+	
+	int prepended_data_len = aes_ecb_detect_prepended_data();
+
+	printf("prepended data len: %i\n", prepended_data_len);
+
+	// so now we now the offset where our data get inserted
+	// ignoring everything befor offset we now have to do the same 
+	// as in task12
+	// well in task13 we make the assumtion that we start at a fresh block
+	// so maybe at some garbage to fill the rest block
+	
+	char *plaintext;
+	crack_aes_ecb(&plaintext, 16, prepended_data_len);
+
+	printf("recovered data:\n%s\n", plaintext);
+}