Sorry, my age may be lower than five. I don&#x27;t understand. You explain that a hash is computed over a string that is the concatenation of a server key, a random number and a client adjusted nonce. you then lost me with the four bytes. I thought that we were talking about a string of chars, not an array of bytes. The nonce is an integer value ? The client then increases the nonce value I guess. But how does the client know it has finished the work ? In the article it is said that the hash value should start with a number of 0 bits. But this occurence is random by definition of the hash. It could never occur with the nonce tested. So sorry, I still don&#x27;t understand it.