Signer::unsign

public function unsign($signedValue, $salt = null)
{
	if (!is_string($signedValue))
		throw new ArgumentTypeException('signedValue', 'string');

	list($value, $signature) = $this->unpack($signedValue);
	if (!$this->verifySignature($value, $signature, $salt))
		throw new BadSignatureException('Signature does not match');

	return $value;
}