replace msleep() by thread signalling in comms.c

[proxmark3-svn] / armsrc / hitag2.c

//-----------------------------------------------------------------------------
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// Hitag2 emulation (preliminary test version)
//
// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
//-----------------------------------------------------------------------------
// Hitag2 complete rewrite of the code
// - Fixed modulation/encoding issues
// - Rewrote code for transponder emulation
// - Added snooping of transponder communication
// - Added reader functionality
//
// (c) 2012 Roel Verdult
//-----------------------------------------------------------------------------

#include "hitag2.h"

#include "proxmark3.h"
#include "usb_cdc.h"
#include "apps.h"
#include "util.h"
#include "hitag.h"
#include "string.h"
#include "BigBuf.h"
#include "fpgaloader.h"
#include "protocols.h"

static bool bQuiet;

static bool bCrypto;
static bool bAuthenticating;
static bool bPwd;
static bool bSuccessful;



struct hitag2_tag {
	uint32_t uid;
	enum {
		TAG_STATE_RESET      = 0x01,       // Just powered up, awaiting GetSnr
		TAG_STATE_ACTIVATING = 0x02 ,      // In activation phase (password mode), sent UID, awaiting reader password
		TAG_STATE_ACTIVATED  = 0x03,       // Activation complete, awaiting read/write commands
		TAG_STATE_WRITING    = 0x04,       // In write command, awaiting sector contents to be written
	} state;
	unsigned int active_sector;
	uint8_t crypto_active;
	uint64_t cs;
	uint8_t sectors[12][4];
};

static struct hitag2_tag tag = {
	.state = TAG_STATE_RESET,
	.sectors = {                         // Password mode:               | Crypto mode:
		[0]  = { 0x02, 0x4e, 0x02, 0x20}, // UID                          | UID
		[1]  = { 0x4d, 0x49, 0x4b, 0x52}, // Password RWD                 | 32 bit LSB key
		[2]  = { 0x20, 0xf0, 0x4f, 0x4e}, // Reserved                     | 16 bit MSB key, 16 bit reserved
		[3]  = { 0x0e, 0xaa, 0x48, 0x54}, // Configuration, password TAG  | Configuration, password TAG
		[4]  = { 0x46, 0x5f, 0x4f, 0x4b}, // Data: F_OK
		[5]  = { 0x55, 0x55, 0x55, 0x55}, // Data: UUUU
		[6]  = { 0xaa, 0xaa, 0xaa, 0xaa}, // Data: ....
		[7]  = { 0x55, 0x55, 0x55, 0x55}, // Data: UUUU
		[8]  = { 0x00, 0x00, 0x00, 0x00}, // RSK Low
		[9]  = { 0x00, 0x00, 0x00, 0x00}, // RSK High
		[10] = { 0x00, 0x00, 0x00, 0x00}, // RCF
		[11] = { 0x00, 0x00, 0x00, 0x00}, // SYNC
	},
};

static enum {
	WRITE_STATE_START = 0x0,
	WRITE_STATE_PAGENUM_WRITTEN,
	WRITE_STATE_PROG
} writestate;


// ToDo: define a meaningful maximum size for auth_table. The bigger this is, the lower will be the available memory for traces.
// Historically it used to be FREE_BUFFER_SIZE, which was 2744.
#define AUTH_TABLE_LENGTH 2744
static uint8_t *auth_table;
static size_t auth_table_pos = 0;
static size_t auth_table_len = AUTH_TABLE_LENGTH;

static uint8_t password[4];
static uint8_t NrAr[8];
static uint8_t key[8];
static uint8_t writedata[4];
static uint64_t cipher_state;

/* Following is a modified version of cryptolib.com/ciphers/hitag2/ */
// Software optimized 48-bit Philips/NXP Mifare Hitag2 PCF7936/46/47/52 stream cipher algorithm by I.C. Wiener 2006-2007.
// For educational purposes only.
// No warranties or guarantees of any kind.
// This code is released into the public domain by its author.

// Single bit Hitag2 functions:

#define i4(x,a,b,c,d)    ((uint32_t)((((x)>>(a))&1)+(((x)>>(b))&1)*2+(((x)>>(c))&1)*4+(((x)>>(d))&1)*8))

static const uint32_t ht2_f4a = 0x2C79;      // 0010 1100 0111 1001
static const uint32_t ht2_f4b = 0x6671;      // 0110 0110 0111 0001
static const uint32_t ht2_f5c = 0x7907287B;  // 0111 1001 0000 0111 0010 1000 0111 1011

static uint32_t _f20(const uint64_t x) {
	uint32_t i5;

	i5 = ((ht2_f4a >> i4(x, 1, 2, 4, 5)) & 1) * 1
		+ ((ht2_f4b >> i4(x, 7,11,13,14)) & 1) * 2
		+ ((ht2_f4b >> i4(x,16,20,22,25)) & 1) * 4
		+ ((ht2_f4b >> i4(x,27,28,30,32)) & 1) * 8
		+ ((ht2_f4a >> i4(x,33,42,43,45)) & 1) * 16;

	return (ht2_f5c >> i5) & 1;
}

static uint64_t _hitag2_init(const uint64_t key, const uint32_t serial, const uint32_t IV) {
	uint32_t i;
	uint64_t x = ((key & 0xFFFF) << 32) + serial;

	for (i = 0; i < 32; i++) {
		x >>= 1;
		x += (uint64_t)(_f20(x) ^ (((IV >> i) ^ (key >> (i+16))) & 1)) << 47;
	}
	return x;
}

static uint64_t _hitag2_round(uint64_t *state) {
	uint64_t x = *state;

	x = (x >>  1) +
		((((x >>  0) ^ (x >>  2) ^ (x >>  3) ^ (x >>  6)
		   ^ (x >>  7) ^ (x >>  8) ^ (x >> 16) ^ (x >> 22)
		   ^ (x >> 23) ^ (x >> 26) ^ (x >> 30) ^ (x >> 41)
		   ^ (x >> 42) ^ (x >> 43) ^ (x >> 46) ^ (x >> 47)) & 1) << 47);

	*state = x;
	return _f20(x);
}

static uint32_t _hitag2_byte(uint64_t *x) {
	uint32_t i, c;
	for (i = 0, c = 0; i < 8; i++) {
		c += (uint32_t) _hitag2_round(x) << (i^7);
	}
	return c;
}

static int hitag2_reset(void) {
	tag.state = TAG_STATE_RESET;
	tag.crypto_active = 0;
	return 0;
}

static int hitag2_init(void) {
	hitag2_reset();
	return 0;
}

static void hitag2_cipher_reset(struct hitag2_tag *tag, const uint8_t *iv) {
	uint64_t key = ((uint64_t)tag->sectors[2][2]) |
		((uint64_t)tag->sectors[2][3] << 8) |
		((uint64_t)tag->sectors[1][0] << 16) |
		((uint64_t)tag->sectors[1][1] << 24) |
		((uint64_t)tag->sectors[1][2] << 32) |
		((uint64_t)tag->sectors[1][3] << 40);
	uint32_t uid = ((uint32_t)tag->sectors[0][0]) |
		((uint32_t)tag->sectors[0][1] << 8) |
		((uint32_t)tag->sectors[0][2] << 16) |
		((uint32_t)tag->sectors[0][3] << 24);
	uint32_t iv_ = (((uint32_t)(iv[0]))) |
		(((uint32_t)(iv[1])) << 8) |
		(((uint32_t)(iv[2])) << 16) |
		(((uint32_t)(iv[3])) << 24);
	tag->cs = _hitag2_init(REV64(key), REV32(uid), REV32(iv_));
}

static int hitag2_cipher_authenticate(uint64_t *cs, const uint8_t *authenticator_is) {
	uint8_t authenticator_should[4];
	authenticator_should[0] = ~_hitag2_byte(cs);
	authenticator_should[1] = ~_hitag2_byte(cs);
	authenticator_should[2] = ~_hitag2_byte(cs);
	authenticator_should[3] = ~_hitag2_byte(cs);
	return (memcmp(authenticator_should, authenticator_is, 4) == 0);
}

static int hitag2_cipher_transcrypt(uint64_t *cs, uint8_t *data, unsigned int bytes, unsigned int bits) {
	int i;
	for (i = 0; i < bytes; i++) data[i] ^= _hitag2_byte(cs);
	for (i = 0; i < bits; i++) data[bytes] ^= _hitag2_round(cs) << (7-i);
	return 0;
}

// Sam7s has several timers, we will use the source TIMER_CLOCK1 (aka AT91C_TC_CLKS_TIMER_DIV1_CLOCK)
// TIMER_CLOCK1 = MCK/2, MCK is running at 48 MHz, Timer is running at 48/2 = 24 MHz
// Hitag units (T0) have duration of 8 microseconds (us), which is 1/125000 per second (carrier)
// T0 = TIMER_CLOCK1 / 125000 = 192
#define T0 192

#define HITAG_FRAME_LEN   20
#define HITAG_T_STOP      36 /* T_EOF should be > 36 */
#define HITAG_T_LOW        8 /* T_LOW should be 4..10 */
#define HITAG_T_0_MIN     15 /* T[0] should be 18..22 */
#define HITAG_T_1_MIN     25 /* T[1] should be 26..30 */
//#define HITAG_T_EOF     40 /* T_EOF should be > 36 */
#define HITAG_T_EOF       80 /* T_EOF should be > 36 */
#define HITAG_T_WAIT_1   200 /* T_wresp should be 199..206 */
#define HITAG_T_WAIT_2    90 /* T_wresp should be 199..206 */
#define HITAG_T_WAIT_MAX 300 /* bit more than HITAG_T_WAIT_1 + HITAG_T_WAIT_2 */
#define HITAG_T_PROG     614

#define HITAG_T_TAG_ONE_HALF_PERIOD     10
#define HITAG_T_TAG_TWO_HALF_PERIOD     25
#define HITAG_T_TAG_THREE_HALF_PERIOD   41
#define HITAG_T_TAG_FOUR_HALF_PERIOD    57

#define HITAG_T_TAG_HALF_PERIOD         16
#define HITAG_T_TAG_FULL_PERIOD         32

#define HITAG_T_TAG_CAPTURE_ONE_HALF    13
#define HITAG_T_TAG_CAPTURE_TWO_HALF    25
#define HITAG_T_TAG_CAPTURE_THREE_HALF  41
#define HITAG_T_TAG_CAPTURE_FOUR_HALF   57

static void hitag_send_bit(int bit) {
	LED_A_ON();
	// Reset clock for the next bit
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;

	// Fixed modulation, earlier proxmark version used inverted signal
	if (bit == 0) {
		// Manchester: Unloaded, then loaded |__--|
		LOW(GPIO_SSC_DOUT);
		while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_HALF_PERIOD);
		HIGH(GPIO_SSC_DOUT);
		while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_FULL_PERIOD);
	} else {
		// Manchester: Loaded, then unloaded |--__|
		HIGH(GPIO_SSC_DOUT);
		while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_HALF_PERIOD);
		LOW(GPIO_SSC_DOUT);
		while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_FULL_PERIOD);
	}
	LED_A_OFF();
}

static void hitag_send_frame(const uint8_t *frame, size_t frame_len)
{
	// Send start of frame
	for(size_t i = 0; i < 5; i++) {
		hitag_send_bit(1);
	}

	// Send the content of the frame
	for (size_t i = 0; i < frame_len; i++) {
		hitag_send_bit((frame[i/8] >> (7-(i%8))) & 0x01);
	}

	// Drop the modulation
	LOW(GPIO_SSC_DOUT);
}

static void hitag2_handle_reader_command(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
	uint8_t rx_air[HITAG_FRAME_LEN];

	// Copy the (original) received frame how it is send over the air
	memcpy(rx_air, rx, nbytes(rxlen));

	if (tag.crypto_active) {
		hitag2_cipher_transcrypt(&(tag.cs), rx, rxlen/8, rxlen%8);
	}

	// Reset the transmission frame length
	*txlen = 0;

	// Try to find out which command was send by selecting on length (in bits)
	switch (rxlen) {
		// Received 11000 from the reader, request for UID, send UID
		case 05: {
			// Always send over the air in the clear plaintext mode
			if (rx_air[0] != HITAG2_START_AUTH) {
				// Unknown frame ?
				return;
			}
			*txlen = 32;
			memcpy(tx, tag.sectors[0], 4);
			tag.crypto_active = 0;
		}
		break;

		// Read/Write command: ..xx x..y  yy with yyy == ~xxx, xxx is sector number
		case 10: {
			unsigned int sector = (~( ((rx[0]<<2) & 0x04) | ((rx[1]>>6) & 0x03) ) & 0x07);
			// Verify complement of sector index
			if (sector != ((rx[0]>>3) & 0x07)) {
				//DbpString("Transmission error (read/write)");
				return;
			}

			switch (rx[0] & 0xC6) {
				// Read command: 11xx x00y
				case HITAG2_READ_PAGE:
					memcpy(tx, tag.sectors[sector], 4);
					*txlen = 32;
					break;

				// Inverted Read command: 01xx x10y
				case HITAG2_READ_PAGE_INVERTED:
					for (size_t i = 0; i < 4; i++) {
						tx[i] = tag.sectors[sector][i] ^ 0xff;
					}
					*txlen = 32;
					break;

				// Write command: 10xx x01y
				case HITAG2_WRITE_PAGE:
					// Prepare write, acknowledge by repeating command
					memcpy(tx, rx, nbytes(rxlen));
					*txlen = rxlen;
					tag.active_sector = sector;
					tag.state = TAG_STATE_WRITING;
					break;

				// Unknown command
				default:
					Dbprintf("Unknown command: %02x %02x", rx[0], rx[1]);
					return;
					break;
			}
		}
		break;

		// Writing data or Reader password
		case 32: {
			if (tag.state == TAG_STATE_WRITING) {
				// These are the sector contents to be written. We don't have to do anything else.
				memcpy(tag.sectors[tag.active_sector], rx, nbytes(rxlen));
				tag.state = TAG_STATE_RESET;
				return;
			} else {
				// Received RWD password, respond with configuration and our password
				if (memcmp(rx, tag.sectors[1], 4) != 0) {
					DbpString("Reader password is wrong");
					return;
				}
				*txlen = 32;
				memcpy(tx, tag.sectors[3], 4);
			}
		}
		break;

		// Received RWD authentication challenge and respnse
		case 64: {
			// Store the authentication attempt
			if (auth_table_len < (AUTH_TABLE_LENGTH-8)) {
				memcpy(auth_table+auth_table_len, rx, 8);
				auth_table_len += 8;
			}

			// Reset the cipher state
			hitag2_cipher_reset(&tag, rx);
			// Check if the authentication was correct
			if (!hitag2_cipher_authenticate(&(tag.cs), rx+4)) {
				// The reader failed to authenticate, do nothing
				Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x Failed!", rx[0], rx[1], rx[2], rx[3], rx[4], rx[5], rx[6], rx[7]);
				return;
			}
			// Succesful, but commented out reporting back to the Host, this may delay to much.
			// Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x OK!",rx[0],rx[1],rx[2],rx[3],rx[4],rx[5],rx[6],rx[7]);

			// Activate encryption algorithm for all further communication
			tag.crypto_active = 1;

			// Use the tag password as response
			memcpy(tx, tag.sectors[3], 4);
			*txlen = 32;
		}
		break;
	}

	//  LogTraceHitag(rx, rxlen, 0, 0, false);
	//  LogTraceHitag(tx, *txlen, 0, 0, true);

	if (tag.crypto_active) {
		hitag2_cipher_transcrypt(&(tag.cs), tx, *txlen/8, *txlen%8);
	}
}

static void hitag_reader_send_bit(int bit) {
	LED_A_ON();
	// Reset clock for the next bit
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;

	// Binary puls length modulation (BPLM) is used to encode the data stream
	// This means that a transmission of a one takes longer than that of a zero

	// Enable modulation, which means, drop the field
	HIGH(GPIO_SSC_DOUT);

	// t_low = 4...10 carrier periods
	while (AT91C_BASE_TC0->TC_CV < T0*6);

	// Disable modulation, just activates the field again
	LOW(GPIO_SSC_DOUT);

	if (bit == 0) {
		// Zero bit: |_-|, T[0] = 18...22 carrier periods
		while (AT91C_BASE_TC0->TC_CV < T0*22);
	} else {
		// One bit: |_--|, T[1] = 26...32 carrier periods
		while (AT91C_BASE_TC0->TC_CV < T0*28);
	}
	LED_A_OFF();
}


static void hitag_reader_send_frame(const uint8_t *frame, size_t frame_len)
{
	// Send the content of the frame
	for(size_t i = 0; i < frame_len; i++) {
		hitag_reader_send_bit((frame[i/8] >> (7-(i%8))) & 0x01);
	}
	// Send EOF
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
	// Enable modulation, which means, drop the field
	HIGH(GPIO_SSC_DOUT);
	// t_low = 4...10 carrier periods
	while (AT91C_BASE_TC0->TC_CV < T0*6);
	// Disable modulation, just activates the field again
	LOW(GPIO_SSC_DOUT);
	// t_stop > 36 carrier periods
	while (AT91C_BASE_TC0->TC_CV < T0*36);
}

size_t blocknr;

//-----------------------------------------------------------------------------
// Hitag2 operations
//-----------------------------------------------------------------------------

static bool hitag2_write_page(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
	switch (writestate) {
		case WRITE_STATE_START:
			tx[0] = HITAG2_WRITE_PAGE | (blocknr << 3) | ((blocknr^7) >> 2);
			tx[1] = ((blocknr^7) << 6);
			*txlen = 10;
			writestate = WRITE_STATE_PAGENUM_WRITTEN;
			break;
		case WRITE_STATE_PAGENUM_WRITTEN:
			// Check if page number was received correctly
			if ((rxlen == 10)
					&& (rx[0] == (HITAG2_WRITE_PAGE | (blocknr << 3) | ((blocknr^7) >> 2)))
					&& (rx[1] == (((blocknr & 0x3) ^ 0x3) << 6))) {
				*txlen = 32;
				memset(tx, 0, HITAG_FRAME_LEN);
				memcpy(tx, writedata, 4);
				writestate = WRITE_STATE_PROG;
			} else {
				Dbprintf("hitag2_write_page: Page number was not received correctly: rxlen=%d rx=%02x%02x%02x%02x",
						rxlen, rx[0], rx[1], rx[2], rx[3]);
				bSuccessful = false;
				return false;
			}
			break;
		case WRITE_STATE_PROG:
			if (rxlen == 0) {
				bSuccessful = true;
			} else {
				bSuccessful = false;
				Dbprintf("hitag2_write_page: unexpected rx data (%d) after page write", rxlen);
			}
			return false;
		default:
			DbpString("hitag2_write_page: Unknown state %d");
			bSuccessful = false;
			return false;
	}

	return true;
}

static bool hitag2_password(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen, bool write) {
	// Reset the transmission frame length
	*txlen = 0;

	if (bPwd && !bAuthenticating && write) {
		if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
			return false;
		}
	} else {
		// Try to find out which command was send by selecting on length (in bits)
		switch (rxlen) {
			// No answer, try to resurrect
			case 0: {
				// Stop if there is no answer (after sending password)
				if (bPwd) {
					DbpString("Password failed!");
					return false;
				}
				tx[0] = HITAG2_START_AUTH;
				*txlen = 5;
			}
			break;

			// Received UID, tag password
			case 32: {
				if (!bPwd) {
					bPwd = true;
					bAuthenticating = true;
					memcpy(tx, password, 4);
					*txlen = 32;
				} else {
					if (bAuthenticating) {
						bAuthenticating = false;
						if (write) {
							if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
								return false;
							}
							break;
						}
					} else {
						memcpy(tag.sectors[blocknr], rx, 4);
						blocknr++;
					}

					if (blocknr > 7) {
						DbpString("Read successful!");
						bSuccessful = true;
						return false;
					}
					tx[0] = HITAG2_READ_PAGE | (blocknr << 3) | ((blocknr^7) >> 2);
					tx[1] = ((blocknr^7) << 6);
					*txlen = 10;
				}
			}
			break;

			// Unexpected response
			default: {
				Dbprintf("Unknown frame length: %d", rxlen);
				return false;
			}
			break;
		}
	}

	return true;
}

static bool hitag2_crypto(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen, bool write) {
	// Reset the transmission frame length
	*txlen = 0;

	if (bCrypto) {
		hitag2_cipher_transcrypt(&cipher_state, rx, rxlen/8, rxlen%8);
	}

	if (bCrypto && !bAuthenticating && write) {
		if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
			return false;
		}
	} else {

		// Try to find out which command was send by selecting on length (in bits)
		switch (rxlen) {
			// No answer, try to resurrect
			case 0: {
				// Stop if there is no answer while we are in crypto mode (after sending NrAr)
				if (bCrypto) {
					// Failed during authentication
					if (bAuthenticating) {
						DbpString("Authentication failed!");
						return false;
					} else {
						// Failed reading a block, could be (read/write) locked, skip block and re-authenticate
						if (blocknr == 1) {
							// Write the low part of the key in memory
							memcpy(tag.sectors[1], key+2, 4);
						} else if (blocknr == 2) {
							// Write the high part of the key in memory
							tag.sectors[2][0] = 0x00;
							tag.sectors[2][1] = 0x00;
							tag.sectors[2][2] = key[0];
							tag.sectors[2][3] = key[1];
						} else {
							// Just put zero's in the memory (of the unreadable block)
							memset(tag.sectors[blocknr], 0x00, 4);
						}
						blocknr++;
						bCrypto = false;
					}
				} else {
					tx[0] = HITAG2_START_AUTH;
					*txlen = 5;
				}
				break;
			}
			// Received UID, crypto tag answer
			case 32: {
				if (!bCrypto) {
					uint64_t ui64key = key[0] | ((uint64_t)key[1]) << 8 | ((uint64_t)key[2]) << 16 | ((uint64_t)key[3]) << 24 | ((uint64_t)key[4]) << 32 | ((uint64_t)key[5]) << 40;
					uint32_t ui32uid = rx[0] | ((uint32_t)rx[1]) << 8 | ((uint32_t)rx[2]) << 16 | ((uint32_t)rx[3]) << 24;
					Dbprintf("hitag2_crypto: key=0x%x%x uid=0x%x", (uint32_t) ((REV64(ui64key)) >> 32), (uint32_t) ((REV64(ui64key)) & 0xffffffff), REV32(ui32uid));
					cipher_state = _hitag2_init(REV64(ui64key), REV32(ui32uid), 0);
					memset(tx, 0x00, 4);
					memset(tx+4, 0xff, 4);
					hitag2_cipher_transcrypt(&cipher_state, tx+4, 4, 0);
					*txlen = 64;
					bCrypto = true;
					bAuthenticating = true;
				} else {
					// Check if we received answer tag (at)
					if (bAuthenticating) {
						bAuthenticating = false;
						if (write) {
							if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
								return false;
							}
							break;
						}
					}
					// stage 2+, got data block
					else {
						// Store the received block
						memcpy(tag.sectors[blocknr], rx, 4);
						blocknr++;
					}
					if (blocknr > 7) {
						DbpString("Read successful!");
						bSuccessful = true;
						return false;
					} else {
						tx[0] = HITAG2_READ_PAGE | (blocknr << 3) | ((blocknr ^ 7) >> 2);
						tx[1] = ((blocknr ^ 7) << 6);
						*txlen = 10;
					}
				}
			}
			break;

			// Unexpected response
			default: {
				Dbprintf("Unknown frame length: %d",rxlen);
				return false;
			}
			break;
		}
	}

	if (bCrypto) {
		// We have to return now to avoid double encryption
		if (!bAuthenticating) {
			hitag2_cipher_transcrypt(&cipher_state, tx, *txlen/8, *txlen%8);
		}
	}

	return true;
}

static bool hitag2_authenticate(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
	// Reset the transmission frame length
	*txlen = 0;

	// Try to find out which command was send by selecting on length (in bits)
	switch (rxlen) {
		// No answer, try to resurrect
		case 0: {
			// Stop if there is no answer while we are in crypto mode (after sending NrAr)
			if (bCrypto) {
				DbpString("Authentication failed!");
				return false;
			}
			tx[0] = HITAG2_START_AUTH;
			*txlen = 5;
		}
		break;

		// Received UID, crypto tag answer
		case 32: {
			if (!bCrypto) {
				memcpy(tx, NrAr, 8);
				*txlen = 64;
				bCrypto = true;
			} else {
				DbpString("Authentication successful!");
				// We are done... for now
				return false;
			}
		}
		break;

		// Unexpected response
		default: {
			Dbprintf("Unknown frame length: %d",rxlen);
			return false;
		}
		break;
	}

	return true;
}

static bool hitag2_test_auth_attempts(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {

	// Reset the transmission frame length
	*txlen = 0;

	// Try to find out which command was send by selecting on length (in bits)
	switch (rxlen) {
		// No answer, try to resurrect
		case 0: {
			// Stop if there is no answer while we are in crypto mode (after sending NrAr)
			if (bCrypto) {
				Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x Failed, removed entry!", NrAr[0], NrAr[1], NrAr[2], NrAr[3], NrAr[4], NrAr[5], NrAr[6], NrAr[7]);

				// Removing failed entry from authentiations table
				memcpy(auth_table+auth_table_pos, auth_table+auth_table_pos+8, 8);
				auth_table_len -= 8;

				// Return if we reached the end of the authentications table
				bCrypto = false;
				if (auth_table_pos == auth_table_len) {
					return false;
				}

				// Copy the next authentication attempt in row (at the same position, b/c we removed last failed entry)
				memcpy(NrAr, auth_table+auth_table_pos, 8);
			}
			tx[0] = HITAG2_START_AUTH;
			*txlen = 5;
		}
		break;

		// Received UID, crypto tag answer, or read block response
		case 32: {
			if (!bCrypto) {
				*txlen = 64;
				memcpy(tx, NrAr, 8);
				bCrypto = true;
			} else {
				Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x OK", NrAr[0], NrAr[1], NrAr[2], NrAr[3], NrAr[4], NrAr[5], NrAr[6], NrAr[7]);
				bCrypto = false;
				if ((auth_table_pos+8) == auth_table_len) {
					return false;
				}
				auth_table_pos += 8;
				memcpy(NrAr, auth_table+auth_table_pos, 8);
			}
		}
		break;

		default: {
			Dbprintf("Unknown frame length: %d",rxlen);
			return false;
		}
		break;
	}

	return true;
}

static bool hitag2_read_uid(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
	// Reset the transmission frame length
	*txlen = 0;

	// Try to find out which command was send by selecting on length (in bits)
	switch (rxlen) {
		// No answer, try to resurrect
		case 0: {
			// Just starting or if there is no answer
			tx[0] = HITAG2_START_AUTH;
			*txlen = 5;
		}
		break;
		// Received UID
		case 32: {
			// Check if we received answer tag (at)
			if (bAuthenticating) {
				bAuthenticating = false;
			} else {
				// Store the received block
				memcpy(tag.sectors[blocknr], rx, 4);
				blocknr++;
			}
			if (blocknr > 0) {
				//DbpString("Read successful!");
				bSuccessful = true;
				return false;
			}
		}
		break;
		// Unexpected response
		default: {
			Dbprintf("Unknown frame length: %d",rxlen);
			return false;
		}
		break;
	}
	return true;
}

void SnoopHitag(uint32_t type) {
	// int frame_count;
	int response;
	int overflow;
	bool rising_edge;
	bool reader_frame;
	int lastbit;
	bool bSkip;
	int tag_sof;
	uint8_t rx[HITAG_FRAME_LEN] = {0};
	size_t rxlen = 0;

	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);

	// Clean up trace and prepare it for storing frames
	set_tracing(true);
	clear_trace();

	auth_table_len = 0;
	auth_table_pos = 0;

	BigBuf_free();
	auth_table = (uint8_t *)BigBuf_malloc(AUTH_TABLE_LENGTH);
	memset(auth_table, 0x00, AUTH_TABLE_LENGTH);

	DbpString("Starting Hitag2 snoop");
	LED_D_ON();

	// Set up eavesdropping mode, frequency divisor which will drive the FPGA
	// and analog mux selection.
	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT  | FPGA_LF_EDGE_DETECT_TOGGLE_MODE);
	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);

	// Configure output pin that is connected to the FPGA (for modulating)
	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;

	// Disable modulation, we are going to eavesdrop, not modulate ;)
	LOW(GPIO_SSC_DOUT);

	// Enable Peripheral Clock for TIMER_CLOCK1, used to capture edges of the reader frames
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
	AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;

	// Disable timer during configuration
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

	// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
	// external trigger rising edge, load RA on rising edge of TIOA.
	AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK | AT91C_TC_ETRGEDG_BOTH | AT91C_TC_ABETRG | AT91C_TC_LDRA_BOTH;

	// Enable and reset counter
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

	// Reset the received frame, frame count and timing info
	// frame_count = 0;
	response = 0;
	overflow = 0;
	reader_frame = false;
	lastbit = 1;
	bSkip = true;
	tag_sof = 4;

	while (!BUTTON_PRESS()) {
		// Watchdog hit
		WDT_HIT();

		// Receive frame, watch for at most T0*EOF periods
		while (AT91C_BASE_TC1->TC_CV < T0*HITAG_T_EOF) {
			// Check if rising edge in modulation is detected
			if (AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
				// Retrieve the new timing values
				int ra = (AT91C_BASE_TC1->TC_RA/T0);

				// Find out if we are dealing with a rising or falling edge
				rising_edge = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_FRAME) > 0;

				// Shorter periods will only happen with reader frames
				if (!reader_frame && rising_edge && ra < HITAG_T_TAG_CAPTURE_ONE_HALF) {
					// Switch from tag to reader capture
					LED_C_OFF();
					reader_frame = true;
					memset(rx, 0x00, sizeof(rx));
					rxlen = 0;
				}

				// Only handle if reader frame and rising edge, or tag frame and falling edge
				if (reader_frame != rising_edge) {
					overflow += ra;
					continue;
				}

				// Add the buffered timing values of earlier captured edges which were skipped
				ra += overflow;
				overflow = 0;

				if (reader_frame) {
					LED_B_ON();
					// Capture reader frame
					if (ra >= HITAG_T_STOP) {
						if (rxlen != 0) {
							//DbpString("wierd0?");
						}
						// Capture the T0 periods that have passed since last communication or field drop (reset)
						response = (ra - HITAG_T_LOW);
					} else if (ra >= HITAG_T_1_MIN) {
						// '1' bit
						rx[rxlen / 8] |= 1 << (7-(rxlen%8));
						rxlen++;
					} else if (ra >= HITAG_T_0_MIN) {
						// '0' bit
						rx[rxlen / 8] |= 0 << (7-(rxlen%8));
						rxlen++;
					} else {
						// Ignore wierd value, is to small to mean anything
					}
				} else {
					LED_C_ON();
					// Capture tag frame (manchester decoding using only falling edges)
					if (ra >= HITAG_T_EOF) {
						if (rxlen != 0) {
							//DbpString("wierd1?");
						}
						// Capture the T0 periods that have passed since last communication or field drop (reset)
						// We always recieve a 'one' first, which has the falling edge after a half period |-_|
						response = ra - HITAG_T_TAG_HALF_PERIOD;
					} else if (ra >= HITAG_T_TAG_CAPTURE_FOUR_HALF) {
						// Manchester coding example |-_|_-|-_| (101)
						rx[rxlen / 8] |= 0 << (7-(rxlen%8));
						rxlen++;
						rx[rxlen / 8] |= 1 << (7-(rxlen%8));
						rxlen++;
					} else if (ra >= HITAG_T_TAG_CAPTURE_THREE_HALF) {
						// Manchester coding example |_-|...|_-|-_| (0...01)
						rx[rxlen / 8] |= 0 << (7-(rxlen%8));
						rxlen++;
						// We have to skip this half period at start and add the 'one' the second time
						if (!bSkip) {
							rx[rxlen / 8] |= 1 << (7-(rxlen%8));
							rxlen++;
						}
						lastbit = !lastbit;
						bSkip = !bSkip;
					} else if (ra >= HITAG_T_TAG_CAPTURE_TWO_HALF) {
						// Manchester coding example |_-|_-| (00) or |-_|-_| (11)
						if (tag_sof) {
							// Ignore bits that are transmitted during SOF
							tag_sof--;
						} else {
							// bit is same as last bit
							rx[rxlen / 8] |= lastbit << (7-(rxlen%8));
							rxlen++;
						}
					} else {
						// Ignore wierd value, is to small to mean anything
					}
				}
			}
		}

		// Check if frame was captured
		if (rxlen > 0) {
			// frame_count++;
			if (!LogTraceHitag(rx, rxlen, response, 0, reader_frame)) {
				DbpString("Trace full");
				break;
			}

			// Check if we recognize a valid authentication attempt
			if (nbytes(rxlen) == 8) {
				// Store the authentication attempt
				if (auth_table_len < (AUTH_TABLE_LENGTH-8)) {
					memcpy(auth_table+auth_table_len,rx,8);
					auth_table_len += 8;
				}
			}

			// Reset the received frame and response timing info
			memset(rx, 0x00, sizeof(rx));
			response = 0;
			reader_frame = false;
			lastbit = 1;
			bSkip = true;
			tag_sof = 4;
			overflow = 0;

			LED_B_OFF();
			LED_C_OFF();
		} else {
			// Save the timer overflow, will be 0 when frame was received
			overflow += (AT91C_BASE_TC1->TC_CV/T0);
		}
		// Reset the frame length
		rxlen = 0;
		// Reset the timer to restart while-loop that receives frames
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG;
	}
	LED_A_ON();
	LED_B_OFF();
	LED_C_OFF();
	LED_D_OFF();
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	LED_A_OFF();

//  Dbprintf("frame received: %d",frame_count);
//  Dbprintf("Authentication Attempts: %d",(auth_table_len/8));
//  DbpString("All done");
}

void SimulateHitagTag(bool tag_mem_supplied, uint8_t *data) {
	// int frame_count;
	int response;
	int overflow;
	uint8_t rx[HITAG_FRAME_LEN];
	size_t rxlen = 0;
	uint8_t tx[HITAG_FRAME_LEN];
	size_t txlen = 0;
	bool bQuitTraceFull = false;
	bQuiet = false;

	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);

	// Clean up trace and prepare it for storing frames
	set_tracing(true);
	clear_trace();

	auth_table_len = 0;
	auth_table_pos = 0;
	uint8_t *auth_table;
	BigBuf_free();
	auth_table = BigBuf_malloc(AUTH_TABLE_LENGTH);
	memset(auth_table, 0x00, AUTH_TABLE_LENGTH);

	DbpString("Starting Hitag2 simulation");
	LED_D_ON();
	hitag2_init();

	if (tag_mem_supplied) {
		DbpString("Loading hitag2 memory...");
		memcpy((uint8_t*)tag.sectors, data, 48);
	}

	uint32_t block = 0;
	for (size_t i = 0; i < 12; i++) {
		for (size_t j = 0; j < 4; j++) {
			block <<= 8;
			block |= tag.sectors[i][j];
		}
		Dbprintf("| %d | %08x |", i, block);
	}

	// Set up simulator mode, frequency divisor which will drive the FPGA
	// and analog mux selection.
	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT);
	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);

	// Configure output pin that is connected to the FPGA (for modulating)
	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;

	// Disable modulation at default, which means release resistance
	LOW(GPIO_SSC_DOUT);

	// Enable Peripheral Clock for TIMER_CLOCK0, used to measure exact timing before answering
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC0);

	// Enable Peripheral Clock for TIMER_CLOCK1, used to capture edges of the reader frames
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
	AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;

	// Disable timer during configuration
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

	// TC0: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
	AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;

	// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
	// external trigger rising edge, load RA on rising edge of TIOA.
	AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK | AT91C_TC_ETRGEDG_RISING | AT91C_TC_ABETRG | AT91C_TC_LDRA_RISING;

	// Reset the received frame, frame count and timing info
	memset(rx, 0x00, sizeof(rx));
	// frame_count = 0;
	response = 0;
	overflow = 0;

	// Enable and reset counter
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

	while (!BUTTON_PRESS()) {
		// Watchdog hit
		WDT_HIT();

		// Receive frame, watch for at most T0*EOF periods
		while (AT91C_BASE_TC1->TC_CV < T0*HITAG_T_EOF) {
			// Check if rising edge in modulation is detected
			if (AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
				// Retrieve the new timing values
				int ra = (AT91C_BASE_TC1->TC_RA/T0) + overflow;
				overflow = 0;

				// Reset timer every frame, we have to capture the last edge for timing
				AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

				LED_B_ON();

				// Capture reader frame
				if (ra >= HITAG_T_STOP) {
					if (rxlen != 0) {
						//DbpString("wierd0?");
					}
					// Capture the T0 periods that have passed since last communication or field drop (reset)
					response = (ra - HITAG_T_LOW);
				} else if (ra >= HITAG_T_1_MIN) {
					// '1' bit
					rx[rxlen / 8] |= 1 << (7-(rxlen%8));
					rxlen++;
				} else if (ra >= HITAG_T_0_MIN) {
					// '0' bit
					rx[rxlen / 8] |= 0 << (7-(rxlen%8));
					rxlen++;
				} else {
					// Ignore wierd value, is to small to mean anything
				}
			}
		}

		// Check if frame was captured
		if (rxlen > 4) {
			// frame_count++;
			if (!bQuiet) {
				if (!LogTraceHitag(rx, rxlen, response, 0, true)) {
					DbpString("Trace full");
					if (bQuitTraceFull) {
						break;
					} else {
						bQuiet = true;
					}
				}
			}

			// Disable timer 1 with external trigger to avoid triggers during our own modulation
			AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

			// Process the incoming frame (rx) and prepare the outgoing frame (tx)
			hitag2_handle_reader_command(rx, rxlen, tx, &txlen);

			// Wait for HITAG_T_WAIT_1 carrier periods after the last reader bit,
			// not that since the clock counts since the rising edge, but T_Wait1 is
			// with respect to the falling edge, we need to wait actually (T_Wait1 - T_Low)
			// periods. The gap time T_Low varies (4..10). All timer values are in
			// terms of T0 units
			while (AT91C_BASE_TC0->TC_CV < T0*(HITAG_T_WAIT_1-HITAG_T_LOW));

			// Send and store the tag answer (if there is any)
			if (txlen) {
				// Transmit the tag frame
				hitag_send_frame(tx, txlen);
				// Store the frame in the trace
				if (!bQuiet) {
					if (!LogTraceHitag(tx, txlen, 0, 0, false)) {
						DbpString("Trace full");
						if (bQuitTraceFull) {
							break;
						} else {
							bQuiet = true;
						}
					}
				}
			}

			// Reset the received frame and response timing info
			memset(rx, 0x00, sizeof(rx));
			response = 0;

			// Enable and reset external trigger in timer for capturing future frames
			AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
			LED_B_OFF();
		}
		// Reset the frame length
		rxlen = 0;
		// Save the timer overflow, will be 0 when frame was received
		overflow += (AT91C_BASE_TC1->TC_CV/T0);
		// Reset the timer to restart while-loop that receives frames
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG;
	}
	LED_B_OFF();
	LED_D_OFF();
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);

	DbpString("Sim Stopped");

}

void ReaderHitag(hitag_function htf, hitag_data *htd) {
	// int frame_count;
	int response;
	uint8_t rx[HITAG_FRAME_LEN];
	size_t rxlen = 0;
	uint8_t txbuf[HITAG_FRAME_LEN];
	uint8_t *tx = txbuf;
	size_t txlen = 0;
	int lastbit;
	bool bSkip;
	int reset_sof;
	int tag_sof;
	int t_wait = HITAG_T_WAIT_MAX;
	bool bStop = false;
	bool bQuitTraceFull = false;

	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	// Reset the return status
	bSuccessful = false;

	// Clean up trace and prepare it for storing frames
	set_tracing(true);
	clear_trace();

	//DbpString("Starting Hitag reader family");

	// Check configuration
	switch (htf) {
		case RHT2F_PASSWORD: {
			Dbprintf("List identifier in password mode");
			memcpy(password, htd->pwd.password, 4);
			blocknr = 0;
			bQuitTraceFull = false;
			bQuiet = false;
			bPwd = false;
			bAuthenticating = false;
		}
		break;
		case RHT2F_AUTHENTICATE: {
			DbpString("Authenticating using nr,ar pair:");
			memcpy(NrAr, htd->auth.NrAr, 8);
			Dbhexdump(8, NrAr, false);
			bQuiet = false;
			bCrypto = false;
			bAuthenticating = false;
			bQuitTraceFull = true;
		}
		break;
		case RHT2F_CRYPTO:
		{
			DbpString("Authenticating using key:");
			memcpy(key, htd->crypto.key, 6);    //HACK; 4 or 6??  I read both in the code.
			Dbhexdump(6, key, false);
			blocknr = 0;
			bQuiet = false;
			bCrypto = false;
			bAuthenticating = false;
			bQuitTraceFull = true;
		}
		break;
		case RHT2F_TEST_AUTH_ATTEMPTS: {
			Dbprintf("Testing %d authentication attempts", (auth_table_len/8));
			auth_table_pos = 0;
			memcpy(NrAr, auth_table, 8);
			bQuitTraceFull = false;
			bQuiet = false;
			bCrypto = false;
		}
		break;
		case RHT2F_UID_ONLY: {
			blocknr = 0;
			bQuiet = false;
			bCrypto = false;
			bAuthenticating = false;
			bQuitTraceFull = true;
		}
		break;
		default: {
			Dbprintf("Error, unknown function: %d", htf);
			return;
		}
		break;
	}

	LED_D_ON();
	hitag2_init();

	// Configure output and enable pin that is connected to the FPGA (for modulating)
	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;

	// Set fpga in edge detect with reader field, we can modulate as reader now
	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT | FPGA_LF_EDGE_DETECT_READER_FIELD);

	// Set Frequency divisor which will drive the FPGA and analog mux selection
	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);

	// Disable modulation at default, which means enable the field
	LOW(GPIO_SSC_DOUT);

	// Enable Peripheral Clock for TIMER_CLOCK0, used to measure exact timing before answering
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC0);

	// Enable Peripheral Clock for TIMER_CLOCK1, used to capture edges of the tag frames
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
	AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;

	// Disable timer during configuration
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

	// TC0: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
	AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;

	// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
	// external trigger rising edge, load RA on falling edge of TIOA.
	AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK | AT91C_TC_ETRGEDG_FALLING | AT91C_TC_ABETRG | AT91C_TC_LDRA_FALLING;

	// Enable and reset counters
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

	// Reset the received frame, frame count and timing info
	// frame_count = 0;
	response = 0;
	lastbit = 1;

	// Tag specific configuration settings (sof, timings, etc.)
	if (htf < 10) {
		// hitagS settings
		reset_sof = 1;
		t_wait = 200;
		//DbpString("Configured for hitagS reader");
	} else if (htf < 20) {
		// hitag1 settings
		reset_sof = 1;
		t_wait = 200;
		//DbpString("Configured for hitag1 reader");
	} else if (htf < 30) {
		// hitag2 settings
		reset_sof = 4;
		t_wait = HITAG_T_WAIT_2;
		//DbpString("Configured for hitag2 reader");
	} else {
		Dbprintf("Error, unknown hitag reader type: %d", htf);
		goto out;
	}

	// wait for tag to power up
	// t_PowerUp = 312,5 carrier periods
	while (AT91C_BASE_TC0->TC_CV < T0*(312-t_wait));

	uint8_t attempt_count = 0;
	while (!bStop && !BUTTON_PRESS()) {
		WDT_HIT();

		// Check if frame was captured and store it
		if (rxlen > 0) {
			// frame_count++;
			if (!bQuiet) {
				if (!LogTraceHitag(rx, rxlen, response, 0, false)) {
					DbpString("Trace full");
					if (bQuitTraceFull) {
						break;
					} else {
						bQuiet = true;
					}
				}
			}
		}

		// By default reset the transmission buffer
		tx = txbuf;
		switch (htf) {
			case RHT2F_PASSWORD: {
				bStop = !hitag2_password(rx, rxlen, tx, &txlen, false);
			}
			break;
			case RHT2F_AUTHENTICATE: {
				bStop = !hitag2_authenticate(rx, rxlen, tx, &txlen);
			}
			break;
			case RHT2F_CRYPTO: {
				bStop = !hitag2_crypto(rx, rxlen, tx, &txlen, false);
			}
			break;
			case RHT2F_TEST_AUTH_ATTEMPTS: {
				bStop = !hitag2_test_auth_attempts(rx, rxlen, tx, &txlen);
			}
			break;
			case RHT2F_UID_ONLY: {
				bStop = !hitag2_read_uid(rx, rxlen, tx, &txlen);
				attempt_count++; //attempt 3 times to get uid then quit
				if (!bStop && attempt_count == 3)
					bStop = true;
			}
			break;
			default: {
				Dbprintf("Error, unknown function: %d", htf);
				goto out;
			}
		}

		// Send and store the reader command
		// Disable timer 1 with external trigger to avoid triggers during our own modulation
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

		// Wait for HITAG_T_WAIT_2 carrier periods after the last tag bit before transmitting,
		// Since the clock counts since the last falling edge, a 'one' means that the
		// falling edge occured halfway the period. with respect to this falling edge,
		// we need to wait (T_Wait2 + half_tag_period) when the last was a 'one'.
		// All timer values are in terms of T0 units
		while (AT91C_BASE_TC0->TC_CV < T0*(t_wait+(HITAG_T_TAG_HALF_PERIOD*lastbit)));

		//Dbprintf("DEBUG: Sending reader frame");

		// Transmit the reader frame
		hitag_reader_send_frame(tx, txlen);

		// Enable and reset external trigger in timer for capturing future frames
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

		// Add transmitted frame to total count
		if (txlen > 0) {
			// frame_count++;
			if (!bQuiet) {
				// Store the frame in the trace
				if (!LogTraceHitag(tx, txlen, HITAG_T_WAIT_2, 0, true)) {
					if (bQuitTraceFull) {
						break;
					} else {
						bQuiet = true;
					}
				}
			}
		}

		// Reset values for receiving frames
		memset(rx, 0x00, sizeof(rx));
		rxlen = 0;
		lastbit = 1;
		bSkip = true;
		tag_sof = reset_sof;
		response = 0;
		//Dbprintf("DEBUG: Waiting to receive frame");
		uint32_t errorCount = 0;

		// Receive frame, watch for at most T0*EOF periods
		while (AT91C_BASE_TC1->TC_CV < T0*HITAG_T_WAIT_MAX) {
			// Check if falling edge in tag modulation is detected
			if (AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
				// Retrieve the new timing values
				int ra = (AT91C_BASE_TC1->TC_RA/T0);

				// Reset timer every frame, we have to capture the last edge for timing
				AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;

				LED_B_ON();

				// Capture tag frame (manchester decoding using only falling edges)
				if (ra >= HITAG_T_EOF) {
					if (rxlen != 0) {
						//Dbprintf("DEBUG: Wierd1");
					}
					// Capture the T0 periods that have passed since last communication or field drop (reset)
					// We always recieve a 'one' first, which has the falling edge after a half period |-_|
					response = ra - HITAG_T_TAG_HALF_PERIOD;
				} else if (ra >= HITAG_T_TAG_CAPTURE_FOUR_HALF) {
					// Manchester coding example |-_|_-|-_| (101)

					//need to test to verify we don't exceed memory...
					//if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//  break;
					//}
					rx[rxlen / 8] |= 0 << (7-(rxlen%8));
					rxlen++;
					rx[rxlen / 8] |= 1 << (7-(rxlen%8));
					rxlen++;
				} else if (ra >= HITAG_T_TAG_CAPTURE_THREE_HALF) {
					// Manchester coding example |_-|...|_-|-_| (0...01)

					//need to test to verify we don't exceed memory...
					//if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//  break;
					//}
					rx[rxlen / 8] |= 0 << (7-(rxlen%8));
					rxlen++;
					// We have to skip this half period at start and add the 'one' the second time
					if (!bSkip) {
						rx[rxlen / 8] |= 1 << (7-(rxlen%8));
						rxlen++;
					}
					lastbit = !lastbit;
					bSkip = !bSkip;
				} else if (ra >= HITAG_T_TAG_CAPTURE_TWO_HALF) {
					// Manchester coding example |_-|_-| (00) or |-_|-_| (11)

					//need to test to verify we don't exceed memory...
					//if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//  break;
					//}
					if (tag_sof) {
						// Ignore bits that are transmitted during SOF
						tag_sof--;
					} else {
						// bit is same as last bit
						rx[rxlen / 8] |= lastbit << (7-(rxlen%8));
						rxlen++;
					}
				} else {
					//Dbprintf("DEBUG: Wierd2");
					errorCount++;
					// Ignore wierd value, is to small to mean anything
				}
			}
			//if we saw over 100 wierd values break it probably isn't hitag...
			if (errorCount > 100) break;
			// We can break this loop if we received the last bit from a frame
			if (AT91C_BASE_TC1->TC_CV > T0*HITAG_T_EOF) {
				if (rxlen > 0) break;
			}
		}
	}

out:
	//Dbprintf("DEBUG: Done waiting for frame");

	LED_B_OFF();
	LED_D_OFF();
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	//Dbprintf("frame received: %d",frame_count);
	//DbpString("All done");
	if (bSuccessful)
		cmd_send(CMD_ACK, bSuccessful, 0, 0, (uint8_t*)tag.sectors, 48);
	else
		cmd_send(CMD_ACK, bSuccessful, 0, 0, 0, 0);
}

void WriterHitag(hitag_function htf, hitag_data *htd, int page) {
	// int frame_count;
	int response;
	uint8_t rx[HITAG_FRAME_LEN];
	size_t rxlen = 0;
	uint8_t txbuf[HITAG_FRAME_LEN];
	uint8_t *tx = txbuf;
	size_t txlen = 0;
	int lastbit;
	bool bSkip;
	int reset_sof;
	int tag_sof;
	int t_wait = HITAG_T_WAIT_MAX;
	bool bStop;
	bool bQuitTraceFull = false;

	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	// Reset the return status
	bSuccessful = false;

	// Clean up trace and prepare it for storing frames
	set_tracing(true);
	clear_trace();

	//DbpString("Starting Hitag reader family");

	// Check configuration
	switch (htf) {
		case WHT2F_CRYPTO: {
			DbpString("Authenticating using key:");
			memcpy(key, htd->crypto.key, 6);    //HACK; 4 or 6??  I read both in the code.
			memcpy(writedata, htd->crypto.data, 4);
			Dbhexdump(6, key, false);
			blocknr = page;
			bQuiet = false;
			bCrypto = false;
			bAuthenticating = false;
			bQuitTraceFull = true;
			writestate = WRITE_STATE_START;
		}
		break;
		case WHT2F_PASSWORD: {
			DbpString("Authenticating using password:");
			memcpy(password, htd->pwd.password, 4);
			memcpy(writedata, htd->crypto.data, 4);
			Dbhexdump(4, password, false);
			blocknr = page;
			bPwd = false;
			bAuthenticating = false;
			writestate = WRITE_STATE_START;
		}
		break;
		default: {
			Dbprintf("Error, unknown function: %d", htf);
			return;
		}
		break;
	}

	LED_D_ON();
	hitag2_init();

	// Configure output and enable pin that is connected to the FPGA (for modulating)
	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;

	// Set fpga in edge detect with reader field, we can modulate as reader now
	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT | FPGA_LF_EDGE_DETECT_READER_FIELD);

	// Set Frequency divisor which will drive the FPGA and analog mux selection
	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);

	// Disable modulation at default, which means enable the field
	LOW(GPIO_SSC_DOUT);

	// Give it a bit of time for the resonant antenna to settle.
	SpinDelay(30);

	// Enable Peripheral Clock for TIMER_CLOCK0, used to measure exact timing before answering
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC0);

	// Enable Peripheral Clock for TIMER_CLOCK1, used to capture edges of the tag frames
	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
	AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;

	// Disable timer during configuration
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

	// TC0: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
	AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;

	// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
	// external trigger rising edge, load RA on falling edge of TIOA.
	AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK | AT91C_TC_ETRGEDG_FALLING | AT91C_TC_ABETRG | AT91C_TC_LDRA_FALLING;

	// Enable and reset counters
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

	// Reset the received frame, frame count and timing info
	// frame_count = 0;
	response = 0;
	lastbit = 1;
	bStop = false;

	// Tag specific configuration settings (sof, timings, etc.)
	if (htf < 10) {
		// hitagS settings
		reset_sof = 1;
		t_wait = 200;
		//DbpString("Configured for hitagS reader");
	} else if (htf < 20) {
		// hitag1 settings
		reset_sof = 1;
		t_wait = 200;
		//DbpString("Configured for hitag1 reader");
	} else if (htf < 30) {
		// hitag2 settings
		reset_sof = 4;
		t_wait = HITAG_T_WAIT_2;
		//DbpString("Configured for hitag2 reader");
	} else {
		Dbprintf("Error, unknown hitag reader type: %d", htf);
		return;
	}
	while (!bStop && !BUTTON_PRESS()) {

		WDT_HIT();

		// Check if frame was captured and store it
		if (rxlen > 0) {
			// frame_count++;
			if (!bQuiet) {
				if (!LogTraceHitag(rx, rxlen, response, 0, false)) {
					DbpString("Trace full");
					if (bQuitTraceFull) {
						break;
					} else {
						bQuiet = true;
					}
				}
			}
		}

		// By default reset the transmission buffer
		tx = txbuf;
		switch (htf) {
			case WHT2F_CRYPTO: {
				bStop = !hitag2_crypto(rx, rxlen, tx, &txlen, true);
			}
			break;
			case WHT2F_PASSWORD: {
				bStop = !hitag2_password(rx, rxlen, tx, &txlen, true);
			}
			break;
			default: {
				Dbprintf("Error, unknown function: %d", htf);
				return;
			}
			break;
		}

		// Send and store the reader command
		// Disable timer 1 with external trigger to avoid triggers during our own modulation
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;

		// Wait for HITAG_T_WAIT_2 carrier periods after the last tag bit before transmitting,
		// Since the clock counts since the last falling edge, a 'one' means that the
		// falling edge occured halfway the period. with respect to this falling edge,
		// we need to wait (T_Wait2 + half_tag_period) when the last was a 'one'.
		// All timer values are in terms of T0 units
		while (AT91C_BASE_TC0->TC_CV < T0*(t_wait+(HITAG_T_TAG_HALF_PERIOD*lastbit)));

		//Dbprintf("DEBUG: Sending reader frame");

		// Transmit the reader frame
		hitag_reader_send_frame(tx, txlen);

		// Enable and reset external trigger in timer for capturing future frames
		AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

		// Add transmitted frame to total count
		if (txlen > 0) {
			// frame_count++;
			if (!bQuiet) {
				// Store the frame in the trace
				if (!LogTraceHitag(tx, txlen, HITAG_T_WAIT_2, 0, true)) {
					if (bQuitTraceFull) {
						break;
					} else {
						bQuiet = true;
					}
				}
			}
		}

		// Reset values for receiving frames
		memset(rx, 0x00, sizeof(rx));
		rxlen = 0;
		lastbit = 1;
		bSkip = true;
		tag_sof = reset_sof;
		response = 0;
		//Dbprintf("DEBUG: Waiting to receive frame");
		uint32_t errorCount = 0;

		// Receive frame, watch for at most T0*EOF periods
		while (AT91C_BASE_TC1->TC_CV < T0*HITAG_T_WAIT_MAX) {
			// Check if falling edge in tag modulation is detected
			if (AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
				// Retrieve the new timing values
				int ra = (AT91C_BASE_TC1->TC_RA/T0);

				// Reset timer every frame, we have to capture the last edge for timing
				AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;

				LED_B_ON();

				// Capture tag frame (manchester decoding using only falling edges)
				if (ra >= HITAG_T_EOF) {
					if (rxlen != 0) {
						//Dbprintf("DEBUG: Wierd1");
					}
					// Capture the T0 periods that have passed since last communication or field drop (reset)
					// We always recieve a 'one' first, which has the falling edge after a half period |-_|
					response = ra - HITAG_T_TAG_HALF_PERIOD;
				} else if (ra >= HITAG_T_TAG_CAPTURE_FOUR_HALF) {
					// Manchester coding example |-_|_-|-_| (101)

					// need to test to verify we don't exceed memory...
					// if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//     break;
					// }
					rx[rxlen / 8] |= 0 << (7-(rxlen%8));
					rxlen++;
					rx[rxlen / 8] |= 1 << (7-(rxlen%8));
					rxlen++;
				} else if (ra >= HITAG_T_TAG_CAPTURE_THREE_HALF) {
					// Manchester coding example |_-|...|_-|-_| (0...01)

					// need to test to verify we don't exceed memory...
					// if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//     break;
					// }
					rx[rxlen / 8] |= 0 << (7-(rxlen%8));
					rxlen++;
					// We have to skip this half period at start and add the 'one' the second time
					if (!bSkip) {
						rx[rxlen / 8] |= 1 << (7-(rxlen%8));
						rxlen++;
					}
					lastbit = !lastbit;
					bSkip = !bSkip;
				} else if (ra >= HITAG_T_TAG_CAPTURE_TWO_HALF) {
					// Manchester coding example |_-|_-| (00) or |-_|-_| (11)

					// need to test to verify we don't exceed memory...
					// if ( ((rxlen+2) / 8) > HITAG_FRAME_LEN) {
					//     break;
					// }
					if (tag_sof) {
						// Ignore bits that are transmitted during SOF
						tag_sof--;
					} else {
						// bit is same as last bit
						rx[rxlen / 8] |= lastbit << (7-(rxlen%8));
						rxlen++;
					}
				} else {
					// Dbprintf("DEBUG: Wierd2");
					errorCount++;
					// Ignore wierd value, it is too small to mean anything
				}
			}
			// if we saw over 100 wierd values break it probably isn't hitag...
			if (errorCount > 100) break;
			// We can break this loop if we received the last bit from a frame
			if (AT91C_BASE_TC1->TC_CV > T0*HITAG_T_EOF) {
				if (rxlen > 0) break;
			}
		}

		// Wait some extra time for flash to be programmed
		if ((rxlen == 0) && (writestate == WRITE_STATE_PROG)) {
			AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
			while (AT91C_BASE_TC0->TC_CV < T0*(HITAG_T_PROG - HITAG_T_WAIT_MAX));
		}
	}
	//Dbprintf("DEBUG: Done waiting for frame");

	LED_B_OFF();
	LED_D_OFF();
	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	//Dbprintf("frame received: %d",frame_count);
	//DbpString("All done");
	cmd_send(CMD_ACK, bSuccessful, 0, 0, (uint8_t*)tag.sectors, 48);
}