I have just been asked by a hotel to email them an authorisation form to secure our accommodation. They will take 1 nights accommodation from our credit card. I have done this in the past by only providing the number on the front but they have asked for the 3 digit number on the back as well. I am thinking this is unsafe and don't feel comfortable providing this. Does anyone know if they actually require this number to do the transaction? The form says they will not secure the booking without the 2 numbers being provided, along with my passport number. Thanks for any advice.