hmac-otp/main.c

#include "main.h"

#define DEBUG

#ifdef DEBUG

#define MYUBRR 8 /*BAUD=115200*/

void initUSART(){
	UBRR0 = (unsigned char) MYUBRR;
	
	/*enable USART write and read*/
	UCSR0B |= /*(1<<RXCIE)|*/(1<<RXEN0)|(1<<TXEN0);
	/*odd parity, 1 stop bit, 8bit words*/
	UCSR0C |= (1<<UPM01)|(1<<UPM00)|(1<<UCSZ01)|(1<<UCSZ00);
}

void tx( char data ){
  while ( !( UCSR0A & (1<<UDRE0)) );
  UDR0 = data;
}

void sendstr( char* str){
	while(str[0]!=0){
		tx(str[0]);
		str++;
	}
}

void sendunum(uint32_t num){
	char text[11] = {0,0,0,0,0,0,0,0,0,0,0};
	uint32_t tmp=1;
	char leadingzero=0;
	char digit=0;
	char i;
	if(num==0){
		tx('0');
		return;
	}
	for(i=1;i<=10;i++){
		digit = '0'+((num/tmp)%10);
		tmp*=10;
		if(digit=='0'){
			leadingzero++;	
		}else{
			leadingzero=0;
		}
		text[10-i]=digit;
	}
	sendstr( text+leadingzero );
}

void tx_hex(uint8_t c){
    if( ((c&0xF0)>>4) <0x0A ){
        tx('0'+((c&0xF0)>>4) );
    }else{
        tx('A'-0x0A+((c&0xF0)>>4));
    }

    if( (c&0x0F)<0x0A ){
        tx('0'+(c&0x0F));
    }else{
        tx('A'-0x0A+(c&0x0F));
    }
}

char rx( void ){
  while ( !(UCSR0A & (1<<RXC0)) );
  return UDR0;
}
#endif //DEBUG

#define SECRET  {'J', 'e', 'f', 'e'};
#define SECLEN  4

#define MSG "what do ya want for nothing?"


int main(void) __attribute__((noreturn));
int __attribute__((OS_main)) main(void) {
    int8_t i;
    uint8_t sec[SECLEN]=SECRET;

	initUSART();
    //sendstr("Hello\n");

    tx('+');

    hmac(MSG,28,sec,4);
    //get_otp_from_cnt(777, 6, sec, SECLEN); //get a 6 digit one-time-password with counter 777
    for(i=0; i<20; i++){                                       
        tx_hex( ((uint8_t*)sha1_digest)[i] );                   
    }
    
    tx('+');
    tx('\n');

    for(;;){

	}
}