function Channel(address to, uint timeout) payable {
  	channelRecipient = to;
  	channelSender = msg.sender; // set channelSender as sender of the message
  	startDate = now; // set startDate as current timestamp
  	channelTimeout = timeout;
  }

  function CloseChannel(bytes32 h, uint8 v, bytes32 r, bytes32 s, uint value){

  	address signer;
  	bytes32 proof;

  	// get signer from signature
  	// ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address): recover address associated with the public key from elliptic curve signature, return zero on error
  	signer = ecrecover(h, v, r, s);

  	// signature is invalid, throw
  	if (signer != channelSender && signer != channelRecipient) throw;

  // keccak256(...) returns (bytes32): compute the Ethereum-SHA-3 (Keccak-256) hash of the (tightly packed) arguments
  // sha3(...) returns (bytes32): an alias to keccak256()
  	proof = sha3(this, value);

  	// signature is valid but doesn't match the data provided
  	if (proof != h) throw;

  	if (signatures[proof] == 0)
  		signatures[proof] = signer;
  	else if (signatures[proof] != signer){
  		// channel completed, both signatures provided
  		if (!channelRecipient.send(value)) throw;
  		selfdestruct(channelSender);
  	}

  }

  function ChannelTimeout(){
  	if (startDate + channelTimeout > now) // check timeout
  		throw;

  	selfdestruct(channelSender);
  }