HASH

HASH

The hash is the product of a one-way mathematical function. It uses a set of variable-length numerical data (characters, such as a password, for example) to produce another set of fixed-length data that has nothing to do with the first, and which does not allow the operation to be repeated in the opposite direction. For example, the hash of "Les Assises de la cybersécurité" is "f0401823bc8e44fcfd99399be0c763ff6f1d195031382272b2808ce6addf56eb" (using the SHA256 algorithm).

While it is trivial to know the hash from the original sentence, the reverse is much more complicated without a pre-calculated dictionary and good computing power. This is why hashes are so widely used to store passwords (but this is not encryption, which would require a secret key), or to produce a signature capable of faithfully representing a set of data (the slightest alteration, however minor, to the source data produces a very different signature).

Bearing in mind that hash is very often used in conjunction with salt and pepper (complementary values), you can see why cybersecurity is often considered to be quite a mess!