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Before tackling the security of systems, it is good to know a little about the different
techniques available to ensure the security of communications. The science studying
secret codes is called cryptography, and the science studying the weaknesses of these
codes is cryptanalysis. They are both intimately linked, of course, and expertise in one
implies a good knowledge of the other. This principle remains general to all security
problems that you may encounter, computer or not; you cannot be a good security
expert without potentially being a good thief. I emphasize the potentially, the goal is
not to be a literal thief, but rather to master the techniques and the way of thinking in
a legal framework.
Cryptography therefore relates, in a broad sense, to information masking techniques.
It is a very old discipline, which has been historically linked to the diplomatic and
military fields for which the secrecy of correspondence is crucial. Today, everyone
uses some form of cryptography, usually without knowing it,your bank card, email
account, Amazon order page and even your login password are based on so-called
cryptographic primitives, i.e. mathematical functions optimized for masking some