From ec17df90f18c0e98c46986b8b0dfb6854cfc8a42 Mon Sep 17 00:00:00 2001
From: n0p <0x90@n0p.cc>
Date: Tue, 17 Oct 2017 20:31:59 +0200
Subject: Init.

---
 encrypt_decoy.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 encrypt_decoy.c

(limited to 'encrypt_decoy.c')

diff --git a/encrypt_decoy.c b/encrypt_decoy.c
new file mode 100644
index 0000000..3cde750
--- /dev/null
+++ b/encrypt_decoy.c
@@ -0,0 +1,80 @@
+/*
+ * gcc encrypt_decoy.c -lcrypto
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "openssl/aes.h"
+
+int main() {
+  AES_KEY enc_key;
+
+  unsigned char plain[80] =
+      "Oh my, there's nothing here... Move along, but don't fall off the "
+      "edge!\0",
+                keys[4][16], cipher[4][80];
+
+  // Getting 4 random 128 bit keys.
+  int fd = open("/dev/urandom", O_RDONLY);
+  if (fd == -1) {
+    exit(-1);
+  }
+
+  for (int i = 0; i < 4; i++) {
+    if (read(fd, keys[i], 16) != 16) {
+      exit(-1);
+    }
+  }
+
+  close(fd);
+
+  // Encrypting the plain text with the 4 keys to 4 cipher texts.
+  for (int i = 0; i < 4; i++) {
+    AES_set_encrypt_key(keys[i], 128, &enc_key);
+
+    for (int j = 0; j < 5; j++) {
+      AES_encrypt(plain + 16 * j, cipher[i] + 16 * j, &enc_key);
+    }
+  }
+
+  // PP the key for copy & paste to the challenge source.
+  for (int i = 0; i < 4; i++) {
+    if (i == 0) {
+      printf("static unsigned char decoy_keys[4][16] = {{");
+    } else {
+      printf("                                          {");
+    }
+
+    for (int j = 0; j < 16; j++) {
+      if (j == 15) {
+        printf("'\\x%02X'", keys[i][j]);
+      } else {
+        printf("'\\x%02X', ", keys[i][j]);
+      }
+    }
+
+    if (i == 3) {
+      printf("}};\n");
+    } else {
+      printf("},\n");
+    }
+  }
+
+  // PP the cipher texts.
+  for (int i = 0; i < 4; i++) {
+    printf("static const unsigned char cipher[80] = {");
+
+    for (int j = 0; j < 80; j++) {
+      if (j == 79) {
+        printf("'\\x%02X'};\n", cipher[i][j]);
+      } else {
+        printf("'\\x%02X', ", cipher[i][j]);
+      }
+    }
+  }
+
+  return 0;
+}
\ No newline at end of file
-- 
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