errors.New("pbkdf2: keyLength too long") } var buf [4]byte dk := make([]byte, 0, numBlocks*hashLen) U := make([]byte, hashLen) for block := 1; block <= numBlocks; block++ { // N.B.: || means concatenation, ^ means XOR // for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter // U_1 = PRF(password, salt || uint(i)) prf.Reset() prf.Write(salt) buf[0] = byte(block >> 24) buf[1] = byte(block >> 16) buf[2] = byte(block >> 8) buf[3] = byte(block) prf.Write(buf[:4]) dk = prf.Sum(dk) T := dk[len(dk)-hashLen:] copy(U, T) // U_n...