How do You Encrypt the Data on the Internet?

Cryptography is the oldest form of encryption. There are traces of its use until 2000 BC This technique still used today, especially on the Web, reveals its mysteries in video thanks to the Kézako program of Unisciel and Lille 1 University.

More and more confidential data is exchanged over the Internet. To give an idea, in France, a commercial transaction takes place every seven seconds on the Web, which is 220 million a year. In order to protect this information, the best solution is to encrypt it.

To do this, you must replace each digit or letter of the message according to a complex mathematical formula. This formula depends on a number named encryption key (or public key). The message is then decoded using a unique decryption key (called private key).

The key to encryption: the mystery of prime numbers
When sending sensitive information, the sender encrypts his message thanks to the encryption key which is public but which does not make it possible to decrypt the message. The decryption key, on the other hand, remains secret. This consists of two prime numbers. The corresponding public key is none other than the multiplication of these two prime numbers.

Only problem, with a technique called “Brute Force”, which consists of testing one by one all combinations, it is possible to find the key. This is why we must choose relatively large numbers so that the calculation is as long as possible, which does not give time to pirates to decode the message …

Kezako is the series that answers the questions of science that everyone asks. In a short, relaxed, minute-long format, the series addresses questions in mathematics, physics, chemistry, computer science, life sciences, and earth sciences. Produced by Unisciel and Lille 1 University, directed by Maxime Beaugeois and Daniel Hennequin, it addresses the principles and applications of science. You can find all the episodes on