SHA (Secure Hash Algorithm) is a family of cryptographic functions from hashage designed by the NSA, allowing the integrity of data to be determined without the need to consult documents. To do so, the SHA function is able to transform a string of characters of random length (a novel, a photo, a music,…) into a string of characters of fixed length (in this case 256 bits for SHA-256, which represents 64 characters). The slightest change, even minor, to the initial character string has an extremely visible effect on the result of the algorithm: the hash of the modified document is totally different from the hash of the original document.