Here is a basic untested code that might do what you're wanting. I combined a my sensors button sketch with the following.
http://www.instructables.com/id/Arduino-door-lock-with-password/
I might build one up at some point, but currently I haven't tested it.

#include <MySensor.h>
#include <SPI.h>
#include <Password.h> //http://playground.arduino.cc/uploads/Code/Password.zip //tells to use password library
#include <Keypad.h> //http://www.arduino.cc/playground/uploads/Code/Keypad.zip  //tells to use keypad library


#define CHILD_ID 3


Password password = Password( "0000" ); //password to unlock, can be changed

const byte ROWS = 4; // Four rows
const byte COLS = 4; // columns
// Define the Keymap
char keys[ROWS][COLS] = {
{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'*','0','#'}
};
// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.
byte rowPins[ROWS] = { 9, 8, 7, 6 };// Connect keypad COL0, COL1 and COL2 to these Arduino pins.
byte colPins[COLS] = { 5, 4, 3 };

MySensor gw;
 
int oldValue=-1;

// Change to V_LIGHT if you use S_LIGHT in presentation below
MyMessage msg(CHILD_ID,V_TRIPPED);
// Create the Keypad
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
void setup()  
{  
  gw.begin();
  delay(200); 
  pinMode(11, OUTPUT);  //green light
  pinMode(12, OUTPUT);  //red light
 
  keypad.addEventListener(keypadEvent); //add an event listener for this keypad

  
  
  // Register binary input sensor to gw (they will be created as child devices)
  // You can use S_DOOR, S_MOTION or S_LIGHT here depending on your usage. 
  // If S_LIGHT is used, remember to update variable type you send in. See "msg" above.
  gw.present(CHILD_ID, S_DOOR);  
}


void loop(){
  keypad.getKey();
  }
  //take care of some special events
  void keypadEvent(KeypadEvent eKey){
  switch (keypad.getState()){
  case PRESSED:
  
  Serial.print("Enter:");
  Serial.println(eKey);
  delay(10);
  
  Serial.write(254);
  
  switch (eKey){
    case '*': checkPassword(); delay(1); break;
    
    case '#': password.reset(); delay(1); break;
    
     default: password.append(eKey); delay(1);
}
}
}
void checkPassword(){
  
if (password.evaluate()){  //if password is right open
    
    Serial.println("Accepted");
    Serial.write(254);delay(10);
    //Add code to run if it works
    gw.send(msg.set(1));
        digitalWrite(11, HIGH);//turn on
    delay(5000); //wait 5 seconds
    digitalWrite(11, LOW);// turn off
    delay(5000);
    gw.send(msg.set(0));
    
}else{
    Serial.println("Denied"); //if passwords wrong keep locked
    Serial.write(254);delay(10);
    //add code to run if it did not work
    gw.send(msg.set(0));
    digitalWrite(12, HIGH); //turn on
    delay(5000); //wait 5 seconds
    digitalWrite(12, LOW);//turn off
    
}
}```

@Anticimex. Software signing is working fine.

Thanks for the information though. I didn't realize the soic 8 couldn't do one wire. It's a ATSHA204-SH-DA-B according to the listing.

EDIT:
Looking at the datasheet, it says that the SCL pin can be ignored for single wire interface. perhaps I'll wire another one up and give it a go.

Just connect, SDA to A3, correct?

I put together a garage door opening using code from korttoma. I used soft signing, and it works great. I was wanting to use a real atsha though.

I bought some atsha204a chips from amazon, and the chips are marked with only "3eas", and a "Y" in one corners. They are soic-8. Is that how this should be marked? I wired one up according to the data sheet. Gnd to Gnd, VCC to 5V, and SDA to A3. I ran the personalizer to generate a key and it said "Failed to wake device." in the serial console. Am I doing something wrong? or did I just get the wrong chip from the seller?

I built this controller using the above code (plus atshasoft signing), and it works great when connected to computer's usb port, but doesn't work when connected to either a USB power adapter, a 12v input on the VIN pin, or 5V on the 5V pin. I'm not sure what could be the issue here. I'm using an arduino nano.

EDIT:
Ignore my stupidity. When you hook up the radio to the 5V instead of the 3.3v output only a PC has a low enough voltage for the (somehow not fried) radio to work. Connecting to the 3v3 works...

Here is a basic untested code that might do what you're wanting. I combined a my sensors button sketch with the following.
http://www.instructables.com/id/Arduino-door-lock-with-password/
I might build one up at some point, but currently I haven't tested it.

#include <MySensor.h>
#include <SPI.h>
#include <Password.h> //http://playground.arduino.cc/uploads/Code/Password.zip //tells to use password library
#include <Keypad.h> //http://www.arduino.cc/playground/uploads/Code/Keypad.zip  //tells to use keypad library


#define CHILD_ID 3


Password password = Password( "0000" ); //password to unlock, can be changed

const byte ROWS = 4; // Four rows
const byte COLS = 4; // columns
// Define the Keymap
char keys[ROWS][COLS] = {
{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'*','0','#'}
};
// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.
byte rowPins[ROWS] = { 9, 8, 7, 6 };// Connect keypad COL0, COL1 and COL2 to these Arduino pins.
byte colPins[COLS] = { 5, 4, 3 };

MySensor gw;
 
int oldValue=-1;

// Change to V_LIGHT if you use S_LIGHT in presentation below
MyMessage msg(CHILD_ID,V_TRIPPED);
// Create the Keypad
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
void setup()  
{  
  gw.begin();
  delay(200); 
  pinMode(11, OUTPUT);  //green light
  pinMode(12, OUTPUT);  //red light
 
  keypad.addEventListener(keypadEvent); //add an event listener for this keypad

  
  
  // Register binary input sensor to gw (they will be created as child devices)
  // You can use S_DOOR, S_MOTION or S_LIGHT here depending on your usage. 
  // If S_LIGHT is used, remember to update variable type you send in. See "msg" above.
  gw.present(CHILD_ID, S_DOOR);  
}


void loop(){
  keypad.getKey();
  }
  //take care of some special events
  void keypadEvent(KeypadEvent eKey){
  switch (keypad.getState()){
  case PRESSED:
  
  Serial.print("Enter:");
  Serial.println(eKey);
  delay(10);
  
  Serial.write(254);
  
  switch (eKey){
    case '*': checkPassword(); delay(1); break;
    
    case '#': password.reset(); delay(1); break;
    
     default: password.append(eKey); delay(1);
}
}
}
void checkPassword(){
  
if (password.evaluate()){  //if password is right open
    
    Serial.println("Accepted");
    Serial.write(254);delay(10);
    //Add code to run if it works
    gw.send(msg.set(1));
        digitalWrite(11, HIGH);//turn on
    delay(5000); //wait 5 seconds
    digitalWrite(11, LOW);// turn off
    delay(5000);
    gw.send(msg.set(0));
    
}else{
    Serial.println("Denied"); //if passwords wrong keep locked
    Serial.write(254);delay(10);
    //add code to run if it did not work
    gw.send(msg.set(0));
    digitalWrite(12, HIGH); //turn on
    delay(5000); //wait 5 seconds
    digitalWrite(12, LOW);//turn off
    
}
}```