set3, completed challenge 21

2 files changed, 69 insertions, 4 deletions

diff --git a/lib/lib3.c b/lib/lib3.c
index 87865ed..43f3ec6 100644
--- a/lib/lib3.c
+++ b/lib/lib3.c
@@ -47,10 +47,6 @@ int cbc_padding_oracle(char *encrypted, int length)
 
 }
 
-int convert_to_little_endian(char *string)
-{
-
-}
 /**
   * format is: 64 nonce concat with 64 bit counter
   * calle has to make sure that nonce is at least 8 bytes
@@ -81,3 +77,55 @@ int aes_ctr(char *in, int length_in, char *out, char *string_key, char *nonce)
 			16, length_last_block);
 
 }
+
+void mt_19937_seed(unsigned int seed)
+{
+	int i;
+
+	__global_mt_19937.index = MT_19937_N;
+	__global_mt_19937.mt[0] = seed;
+	memset(&__global_mt_19937.mt[1], 0, 623);
+	for(i=1;i<=MT_19937_N;i++) {
+		__global_mt_19937.mt[i] = (1812433253 * (__global_mt_19937.mt[i-1]
+			^ (__global_mt_19937.mt[i-1] >> 30))) + i;
+		// only the last 32 bit
+		__global_mt_19937.mt[i] &= 0xFFFFFFFF;
+	}
+}
+
+void mt_19937_generate()
+{
+	unsigned int i, x;
+
+	for(i=0;i<=MT_19937_N;i++) {
+		x = (((__global_mt_19937.mt[i] & MT_19937_UPPER_MASK) + 
+			(__global_mt_19937.mt[(i+1) % 624] & MT_19937_LOWER_MASK)
+		   	)& 0xFFFFFFFF);
+		
+		__global_mt_19937.mt[i] = __global_mt_19937.mt[(i+397) % MT_19937_N] ^ x >> 1;	
+
+		if (x % 2)
+			__global_mt_19937.mt[i] ^= 0x9908b0df;
+	}
+	__global_mt_19937.index = 0;
+}
+
+
+int mt_19937()
+{
+	unsigned int y = 0x0;
+
+	if(__global_mt_19937.index >= MT_19937_N)
+		mt_19937_generate();
+
+	y = __global_mt_19937.mt[__global_mt_19937.index];
+
+	y = y ^ (y >> 11);
+	y = y ^ ((y << 7) & 0x9D2C5680);
+	y = y ^ ((y << 15) & 0xEFC60000);
+	y = y ^ (y >> 18);
+
+	__global_mt_19937.index++;
+
+	return (y & 0xFFFFFFFF);
+}
diff --git a/lib/lib3.h b/lib/lib3.h
index 3078cfe..8adbbb9 100644
--- a/lib/lib3.h
+++ b/lib/lib3.h
@@ -8,9 +8,26 @@
 
 #define BLOCKSIZE 16
 
+#define MT_19937_N 624
+// needed for initialization
+#define MT_19937_F 0x6C078965
+// word size
+#define MT_19937_W 32
+#define MT_19937_UPPER_MASK 0x80000000
+#define MT_19937_LOWER_MASK 0x7fffffff
+
+struct mt_19937_state {
+	unsigned int mt[MT_19937_N];
+	unsigned int index;
+};
+
+struct mt_19937_state __global_mt_19937;
+
 char *challenge17_encrypt(int *length);
 int cbc_padding_oracle(char *encrypted, int length);
 int aes_ctr(char *in, int length_in, char *out, char *string_key, char *nonce);
 
+void mt_19937_seed(unsigned int seed);
+int mt_19937();
 
 #endif