In the recent years, several authors developed braid-based cryptographical protocols. The talk will aim at giving a general overview of the field, insisting on the various cryptographical questions one has to address, and on the theoretical and practical problems arising from using braids: choice of a difficult problem (often conjugacy, but other primitives are possible), representation of the data (normal vs. reduced forms), security proofs (lower complexity bounds, problem with the notion of a random braid), choice of the keys, possible attacks.