Randomize stepping.

frontend/src/main.c

@@ -60,7 +60,7 @@ static int weak_passphrase(const CHR *str)
 
 static int encrypt(const char* const passphrase, const CHR* const input, const CHR* const output)
 {
-	mcrypt_t ctx = NULL;
+	mcrypt_t ctx = MCRYPT_NULL;
 	FILE *fin = NULL, *fout = NULL;
 	int result = 1;
 
@@ -181,7 +181,7 @@ clean_up:
 
 static int decrypt(const char* const passphrase, const CHR* const input, const CHR* const output)
 {
-	mcrypt_t ctx = NULL;
+	mcrypt_t ctx = MCRYPT_NULL;
 	FILE *fin = NULL, *fout = NULL;
 	int result = 1;
 
@@ -312,7 +312,7 @@ static int self_test(void)
 	
 	const size_t length = strlen(text_plain) + 1U;
 	int result = 1;
-	mcrypt_t ctx_enc = NULL, ctx_dec = NULL;
+	mcrypt_t ctx_enc = MCRYPT_NULL, ctx_dec = MCRYPT_NULL;
 
 	FPUTS(T("Self-test is running, please be patient... "), stderr);
 

libMCrypt/include/mcrypt.h

@@ -15,7 +15,8 @@ extern const char* const LIBMCRYPT_BUILDNO;
 /*
  * Opaque handle to internal state
  */
-typedef void* mcrypt_t;
+typedef uintptr_t mcrypt_t;
+#define MCRYPT_NULL ((mcrypt_t)NULL)
 
 /*
  * Seed generator
@@ -23,9 +24,10 @@ typedef void* mcrypt_t;
 int mcrypt_generate_seed(uint64_t* const seed);
 
 /*
- * Allocate or free state
+ * Allocate, reset or free state
  */
 mcrypt_t mcrypt_alloc(const uint64_t salt, const char* const passphrase);
+int mcrypt_reset(const mcrypt_t context, const uint64_t salt, const char* const passphrase);
 void mcrypt_free(const mcrypt_t context);
 
 /*

libMCrypt/src/mcrypt.c

@@ -15,10 +15,11 @@ const char* const LIBMCRYPT_BUILDNO = __DATE__", "__TIME__;
 
 typedef struct
 {
-	uint8_t box[256U][256U];
+	uint8_t wheel_fwd[256U][256U];
-	uint8_t inv[256U][256U];
+	uint8_t wheel_bwd[256U][256U];
-	uint8_t off[256U];
+	uint8_t rot[256U];
-	uint8_t pos;
+	uint8_t step[256U];
+	uint8_t counter;
 }
 crypt_state_t;
 
@@ -95,28 +96,37 @@ static void random_seed(rand_state_t* const state, const uint64_t salt, const ui
 
 static void initialize_state(crypt_state_t* const crypt_state, const uint64_t salt, const uint8_t* const key, const size_t key_len)
 {
+	crypt_state->counter = 0U;
 	rand_state_t rand_state;
 	for (size_t r = 0U; r < 256U; ++r)
 	{
 		random_seed(&rand_state, salt, (uint16_t)r, key, key_len);
-		crypt_state->off[r] = (uint8_t)random_next(&rand_state);
+		crypt_state->rot[r] = (uint8_t)random_next(&rand_state);
 		for (size_t i = 0U; i < 256U; ++i)
 		{
 			const size_t j = random_next(&rand_state) % (i + 1U);
 			if (j != i)
 			{
-				crypt_state->box[r][i] = crypt_state->box[r][j];
+				crypt_state->wheel_fwd[r][i] = crypt_state->wheel_fwd[r][j];
 			}
-			crypt_state->box[r][j] = (uint8_t)i;
+			crypt_state->wheel_fwd[r][j] = (uint8_t)i;
 		}
 		for (size_t i = 0U; i < 256U; ++i)
 		{
-			const size_t j = crypt_state->box[r][i];
+			const size_t j = crypt_state->wheel_fwd[r][i];
-			crypt_state->inv[r][j] = (uint8_t)i;
+			crypt_state->wheel_bwd[r][j] = (uint8_t)i;
 		}
 	}
 	random_seed(&rand_state, salt, 0x0100, key, key_len);
-	crypt_state->pos = (uint8_t)random_next(&rand_state);
+	for (size_t i = 0U; i < 256U; ++i)
+	{
+		const size_t j = random_next(&rand_state) % (i + 1U);
+		if (j != i)
+		{
+			crypt_state->step[i] = crypt_state->step[j];
+		}
+		crypt_state->step[j] = (uint8_t)i;
+	}
 	mcrypt_bzero(&rand_state, sizeof(rand_state_t));
 }
 
@@ -128,9 +138,9 @@ static uint8_t process_enc(crypt_state_t* const crypt_state, uint8_t value)
 {
 	for (size_t i = 0U; i < 256U; ++i)
 	{
-		value = crypt_state->box[i][(value + crypt_state->off[i]) & 0xFF];
+		value = crypt_state->wheel_fwd[i][(value + crypt_state->rot[i]) & 0xFF];
 	}
-	++crypt_state->off[crypt_state->pos++];
+	++crypt_state->rot[crypt_state->step[crypt_state->counter++]];
 	return value;
 }
 
@@ -139,9 +149,9 @@ static uint8_t process_dec(crypt_state_t* const crypt_state, uint8_t value)
 	size_t i = 256U;
 	while (i--)
 	{
-		value = (crypt_state->inv[i][value] - crypt_state->off[i]) & 0xFF;
+		value = (crypt_state->wheel_bwd[i][value] - crypt_state->rot[i]) & 0xFF;
 	}
-	++crypt_state->off[crypt_state->pos++];
+	++crypt_state->rot[crypt_state->step[crypt_state->counter++]];
 	return value;
 }
 
@@ -173,10 +183,21 @@ mcrypt_t mcrypt_alloc(const uint64_t salt, const char* const passphrase)
 	return ((mcrypt_t)state);
 }
 
+int mcrypt_reset(const mcrypt_t context, const uint64_t salt, const char* const passphrase)
+{
+	crypt_state_t* const state = (crypt_state_t*)context;
+	if ((!state) || (!passphrase))
+	{
+		return -1;
+	}
+	initialize_state(state, salt, (uint8_t*)passphrase, strlen(passphrase));
+	return 0;
+}
+
 int mcrypt_enc_process(const mcrypt_t context, const uint8_t* const input, uint8_t* const output, size_t length)
 {
 	crypt_state_t* const state = (crypt_state_t*)context;
-	if (!context)
+	if (!state)
 	{
 		return -1;
 	}
@@ -190,7 +211,7 @@ int mcrypt_enc_process(const mcrypt_t context, const uint8_t* const input, uint8
 int mcrypt_enc_process_inplace(const mcrypt_t context, uint8_t* const buffer, size_t length)
 {
 	crypt_state_t* const state = (crypt_state_t*)context;
-	if (!context)
+	if (!state)
 	{
 		return -1;
 	}
@@ -205,7 +226,7 @@ int mcrypt_enc_process_inplace(const mcrypt_t context, uint8_t* const buffer, si
 int mcrypt_dec_process(const mcrypt_t context, const uint8_t* const input, uint8_t* const output, size_t length)
 {
 	crypt_state_t* const state = (crypt_state_t*)context;
-	if (!context)
+	if (!state)
 	{
 		return -1;
 	}
@@ -219,7 +240,7 @@ int mcrypt_dec_process(const mcrypt_t context, const uint8_t* const input, uint8
 int mcrypt_dec_process_inplace(const mcrypt_t context, uint8_t* const buffer, size_t length)
 {
 	crypt_state_t* const state = (crypt_state_t*)context;
-	if (!context)
+	if (!state)
 	{
 		return -1;
 	}
@@ -233,9 +254,9 @@ int mcrypt_dec_process_inplace(const mcrypt_t context, uint8_t* const buffer, si
 void mcrypt_free(const mcrypt_t context)
 {
 	crypt_state_t* const state = (crypt_state_t*)context;
-	if (context)
+	if (state)
 	{
-		mcrypt_bzero((void*)context, sizeof(crypt_state_t));
+		mcrypt_bzero(state, sizeof(crypt_state_t));
-		free(context);
+		free(state);
 	}
 }