|Cache timing attacks have been proposed in 2005 as a new type of side-channel attack. As it turns out, the Advanced Encryption Standard (AES) is particularly vulnerable to this type of attack. In scenarios where the attack is applicable, countermeasures are very difficult to apply. In this lecture, we will first review what cache timing attacks are and how they can affect the security of the AES. We then proceed to consider cache timing attacks against stream ciphers. The resistance of a number of stream cipher proposals in the eStream project is discussed. Finally, we propose some techniques that can be used by cipher designers to make cache timing attacks more difficult.