// Tests if the encoding process correctly decodes the id back to the original.
func TestEncoding(t *testing.T) {
for i := 0; i < 15; i++ { //How many times we want to run GenerateSeed()
o, _, _ := GenerateSeed(nil)
c := 10
h := 100 //How many random numbers to select in between 0-c and (MAX_INT-c) - MAX-INT
var y []uint64 //Stores all the values we want to run encoding tests on
for t := 0; t < c; t++ {
y = append(y, uint64(t))
}
//Generate Random numbers
for t := 0; t < h; t++ {
upper := *big.NewInt(int64(MAX_INT - 2*c))
rand, _ := rand.Int(rand.Reader, &upper)
randomNumber := rand.Uint64() + uint64(c)
y = append(y, randomNumber)
}
for t := MAX_INT; t >= MAX_INT-c; t-- {
y = append(y, uint64(t))
}
t.Logf("Prime: %d ModInverse: %d Random: %d", o.Prime(), o.ModInverse(), o.Random())
for _, value := range y {
orig := value
hashed := o.Encode(value)
unhashed := o.Decode(hashed)
if orig != unhashed {
t.Errorf("%d: %d -> %d - FAILED", orig, hashed, unhashed)
} else {
t.Logf("%d: %d -> %d - PASSED", orig, hashed, unhashed)
// log.Printf("%d: %d -> %d - PASSED", orig, hashed, unhashed)
}
}
}
}
// Generates a valid Optimus struct using a randomly selected prime
// number from this site: http://primes.utm.edu/lists/small/millions/
// The first 50 million prime numbers are distributed evenly in 50 files.
// Parameter req should be nil if not using Google App Engine.
// This Function is Time, Memory and CPU intensive. Run it once to generate the
// required seeds.
// WARNING: Potentially Insecure. Double check that the prime number returned
// is actually prime number using an independent source.
// The largest Prime has 9 digits. The smallest has 1 digit.
// The final return value is the website zip file identifier that was used to obtain the prime number
func GenerateSeed(req *http.Request) (*Optimus, error, uint8) {
log.Printf("\x1b[31mWARNING: Optimus generates a random number via this site: http://primes.utm.edu/lists/small/millions/. This is potentially insecure!\x1b[39;49m")
baseURL := "http://primes.utm.edu/lists/small/millions/primes%d.zip"
//Generate Random number between 1-50
b_49 := *big.NewInt(49)
n, _ := rand.Int(rand.Reader, &b_49)
i_n := n.Uint64() + 1
//Download zip file
finalUrl := fmt.Sprintf(baseURL, i_n)
log.Printf("Using file: %s", finalUrl)
resp, err := client(req).Get(finalUrl)
if err != nil {
return nil, jsonerror.New(1, "Could not generate seed", err.Error()), uint8(i_n)
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, jsonerror.New(1, "Could not generate seed", err.Error()), uint8(i_n)
}
r, err := zip.NewReader(bytes.NewReader(body), resp.ContentLength)
if err != nil {
return nil, jsonerror.New(1, "Could not generate seed", err.Error()), uint8(i_n)
}
zippedFile := r.File[0]
src, err := zippedFile.Open() //src contains ReaderCloser
if err != nil {
return nil, jsonerror.New(1, "Could not generate seed", err.Error()), uint8(i_n)
}
defer src.Close()
//Create a Byte Slice
buf := new(bytes.Buffer)
noOfBytes, _ := buf.ReadFrom(src)
b := buf.Bytes() //Byte Slice
//Randomly pick a character position
start := 67 // Each zip file has an introductory header which is not relevant until the 67th character
end := noOfBytes
b_end := *big.NewInt(int64(end) - int64(start))
n, _ = rand.Int(rand.Reader, &b_end)
randomPosition := n.Uint64() + uint64(start)
min := randomPosition - 9
max := randomPosition + 9
if min < uint64(start) {
min = uint64(start)
}
if max > uint64(end) {
max = uint64(end)
}
scanner := bufio.NewScanner(strings.NewReader(string(b[min:max]))) //Input
scanner.Split(bufio.ScanWords)
var selectedNumbers []uint64
for scanner.Scan() {
p, _ := strconv.ParseUint(scanner.Text(), 10, 64)
selectedNumbers = append(selectedNumbers, p)
}
//Not perfect but good enough
var selectedPrime uint64
length := len(selectedNumbers)
if length > 2 {
//Pick middle number
//Check if length is even number
//Check if round is odd or even
var odd bool
if length&1 != 0 {
odd = true //odd
} else {
odd = false //even
}
if odd {
selectedPrime = selectedNumbers[length/2]
} else {
r := *big.NewInt(1)
rn, _ := rand.Int(rand.Reader, &r)
if rn.Uint64() == 0 {
selectedPrime = selectedNumbers[length/2]
} else {
selectedPrime = selectedNumbers[length/2-1]
}
}
} else {
//Pick largest number
largest := selectedNumbers[0]
for _, value := range selectedNumbers {
if value > largest {
largest = value
}
}
selectedPrime = largest
}
//Calculate Mod Inverse for selectedPrime
modInverse := ModInverse(selectedPrime)
//Generate Random Integer less than MAX_INT
upper := *big.NewInt(MAX_INT - 2)
rand, _ := rand.Int(rand.Reader, &upper)
randomNumber := rand.Uint64() + 1
return &Optimus{selectedPrime, modInverse, randomNumber}, nil, uint8(i_n)
}
