Hi. Have you seen the conversation between Roman and Anna? Roman was very happy because Anna felt that cryptography is similar to security. Let's go to study a little bit about cryptography to understand if it's true or not. Currently, there are a lot of different products that say that cryptography is very similar to security or even is equal to security. So it's very common to have a question like this. Do you want to create your files to guarantee your privacy in the application? Of course, we have to answer yes. But the reality is that cryptography is not security. You have to be very careful with that because maybe you are thinking that you have a complete privacy in your application and really not because cryptography is not security. Let's go to see a little of details in order to understand why. We are going to define at first what is encryption. Encryption is information of a message to prevent the read by unauthorized entities. So we have a model of encryption here. We have a model of encryption and decryption. We have a message, and we transfer the message to encryption in an encrypted message. So in order to allow the encryption, we use a key. So we have the message as input. We have the transformation that this encryption using a key until you attain the encrypted message. The encrypted message is protected, so anyone can't read that message unless they can make the decryption process. In the decryption process, we use the encrypted message or a key that usually has the same key that encryption and we obtain the original message. So this is a common process of encryption and it works really well because once you have the encrypted message, it's really hard to obtain the original message without a key. So it works, and it works very well. So if it works, why are we saying that encryption is not security? Let's go to remark this word, unauthorized. I am going to make you a question, who is an authorized entity in our data? Have you thought? Let's go for the answer. We have two different answer. Who is the authorized entity in theory, and who is the authorized entity in practice? So in theory, in theory are people with whom you want to share the message. I can authorize to wherever person I want. Just say, "I want for example Anna, read my messages." But in practice is different. Because in practice, the authorized person is wherever, anyone, a person that has a key. If you have the key, you are an authorized person. That's the real problem of encryption. Because when you have an esteem like this, you have increasing process, you can't of course attack the encrypted message. You can try to attain the original message or just encryption message without the key. But it's really hard. It's possible sometimes, but it's really hard today. So hackers usually don't attack the encrypted message. Hackers usually attack the keys. We have to serve the key, we have to manage the key, we have to start the key. So at conclusions, the most important thing now in encryption, is how is made the key management. How the key is stored and how the key is served. We are going to talk a little bit more about that in next series. See you then.