From 95b1e82c4fca864600108d4e36ceadbb290a76f3 Mon Sep 17 00:00:00 2001
From: Benedict <benedict@0xb8000.de>
Date: Sat, 19 Mar 2016 22:44:50 +0100
Subject: set1, challenge 8 completed

---
 set1/Makefile |  6 ++++--
 set1/task8.c  | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 set1/task8.c

(limited to 'set1')

diff --git a/set1/Makefile b/set1/Makefile
index 6c0f149..0d08451 100644
--- a/set1/Makefile
+++ b/set1/Makefile
@@ -2,7 +2,7 @@ LIB=../lib/lib.c
 CC=gcc
 CFLAGS := -g -Wall $(CFLAGS) 
 
-all: task1 task2 task4 task5 task6 task7
+all: task1 task2 task4 task5 task6 task7 task8
 
 task1:
 	$(CC) $(CFLAGS) task1.c $(LIB) -o task1
@@ -21,5 +21,7 @@ task6:
 
 task7:
 	$(CC) $(CFLAGS) task7.c `pkg-config --cflags --libs libcrypto` -o task7
+task8:
+	$(CC) $(CFLAGS) task8.c $(LIB) -o task8
 clean:
-	rm task1 task2 task4 task5 task6 task7
+	rm task1 task2 task4 task5 task6 task7 task8
diff --git a/set1/task8.c b/set1/task8.c
new file mode 100644
index 0000000..98b3380
--- /dev/null
+++ b/set1/task8.c
@@ -0,0 +1,55 @@
+#include "../lib/lib.h"
+
+
+int main(int arc, char **argv)
+{
+	// detect AEC in ECB mode, do NOT break it
+	int number_blocks, i, j, k, read = 0;
+	size_t len = 0;
+	int max_hits = 0, hits = 0, line_number= 0, aes_ecb_line = 0;
+	char *line_hex = NULL;
+	// read file
+	FILE *f = fopen("8.txt", "r");
+
+	if (f == NULL) {
+		perror("failed to open 8.txt");
+		exit(1);
+	}
+
+	while( (read = getline(&line_hex, &len, f)) != -1) {
+		// line is hex encoded 
+		char *line = malloc(read/2+1);
+
+		decode_hex_string(line_hex, line);
+
+		number_blocks = read / 2 / 16;
+		// count 16 byte blocks which are equal
+		for(i=0;i<number_blocks;i++) {
+			for(j=1;j<number_blocks;j++) {
+				for(k=0;k<16;k++) {
+					if(line[i*16+k] != line[j*16+k])
+						break;
+
+					if ( k == 15)
+						hits++;
+				}
+			}
+		}
+		printf("line: %i, hits: %i\n", line_number, hits);
+		if (hits > max_hits) {
+			max_hits = hits;
+			aes_ecb_line = line_number;
+		}
+		line_number++;
+		hits = 0;
+		free(line_hex);
+		free(line);
+		// set line and len to null
+		line = NULL;
+		len = 0;
+	}
+
+	printf("found AES-128-ECB at line: %i\n with %i hits", aes_ecb_line, max_hits);
+
+	return 0;
+}
-- 
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