Two linear codes are permutation-equivalent if they are equal up to a fixed permutation of the codewords coordinates. We present here an algorithm able to compute this permutation. We introduce the concept of signature: a property of a position of a code such that the set of all signatures of a given code is globally invariant by permutation. To compute the permutati- on between two equivalent codes, one needs a signature which is both discrimin- ant and easy to compute. The weight enumerator of the hull of a code provides a signature which has such properties in most cases.