func cache(z *big.Int, filename string) (err error) {
var b []byte
if b, err = z.GobEncode(); err == nil {
err = ioutil.WriteFile(filename, b, 0644)
}
return
}
// Just like Split, but return an error when receiving a kill signal from t.
func splitOrQuit(z *big.Int, quit <-chan time.Time) (p, q *big.Int, err error) {
q, r := big.NewInt(0), big.NewInt(0)
if z.Sign() == 0 {
return
}
max := roughSqrt(z)
primes := sieve.BigSieve()
for {
select {
case <-quit:
err = ErrTimeout
return
case p = <-primes:
if q.DivMod(z, p, r); r.Sign() == 0 {
return
}
if max.Cmp(p) == -1 {
q.SetInt64(1)
p.Set(z)
return
}
}
}
return
}
// For each input modulus 'x' and remainderTree parent 'y', compute z = (y%(x*x))/x; gcd(z, x)
func lowmemRemainderTreeFinal(input, moduli chan *gmp.Int, output chan<- Collision) {
defer close(output)
tmp := new(gmp.Int)
for y := range input {
for i := 0; i < 2; i++ {
modulus, ok := <-moduli
if !ok {
log.Print("Odd number of moduli? (should only see this once)")
continue
}
tmp.Mul(modulus, modulus)
tmp.Rem(y, tmp)
tmp.Quo(tmp, modulus)
if tmp.GCD(nil, nil, tmp, modulus).BitLen() != 1 {
q := new(gmp.Int).Quo(modulus, tmp)
output <- Collision{
Modulus: modulus,
P: tmp,
Q: q,
}
tmp = new(gmp.Int)
}
}
y.Clear()
}
}
// For each productTree node 'x', and remainderTree parent 'y', compute y%(x*x)
func remainderTreeLevel(tree [][]*gmp.Int, level int, wg *sync.WaitGroup, start, step int) {
prevLevel := tree[level+1]
thisLevel := tree[level]
tmp := new(gmp.Int)
for i := start; i < len(thisLevel); i += step {
x := thisLevel[i]
y := prevLevel[i/2]
tmp.Mul(x, x)
x.Rem(y, tmp)
}
wg.Done()
}
func tmpfileReadWriter(ch fileChannels) {
tmpFile, err := ioutil.TempFile(".", "product")
if err != nil {
log.Panic(err)
}
length := make([]byte, 8)
var writeCount uint64
for inData := range ch.writeChan {
buf := inData.Bytes()
encodeLength(length, len(buf))
if _, err := tmpFile.Write(length); err != nil {
log.Panic(err)
}
if _, err := tmpFile.Write(buf); err != nil {
log.Panic(err)
}
inData.Clear()
writeCount += 1
}
if newOffset, e := tmpFile.Seek(0, 0); e != nil || newOffset != 0 {
log.Panic(e)
}
var readCount uint64
m := new(gmp.Int)
for {
if _, e := io.ReadFull(tmpFile, length); e != nil {
if e == io.EOF {
break
}
log.Panic(e)
}
buf := make([]byte, decodeLength(length))
if _, e := io.ReadFull(tmpFile, buf); e != nil {
log.Panic(e)
}
readCount += 1
ch.readChan <- m.SetBytes(buf)
m = new(gmp.Int)
}
if writeCount != readCount {
log.Panicf("Didn't write as many as we read: write=%v read=%v", writeCount, readCount)
}
close(ch.readChan)
syscall.Unlink(tmpFile.Name())
// tmpFile.Truncate(0);
}
// For each productTree node 'x', and remainderTree parent 'y', compute y%(x*x)
func lowmemRemainderTreeLevel(input chan *gmp.Int, productTree []fileChannels, finalOutput chan<- Collision) {
tmp := new(gmp.Int)
ch := productTree[len(productTree)-1]
productTree = productTree[:len(productTree)-1]
// We close the fileWriteChannel here so it kicks off reading now, instead of starting too early
products := ch.readChan
output := make(chan *gmp.Int, 2)
defer close(output)
if len(productTree) == 0 {
ch.StartProducing()
lowmemRemainderTreeFinal(input, products, finalOutput)
return
} else {
go lowmemRemainderTreeLevel(output, productTree, finalOutput)
}
for y := range input {
ch.StartProducing()
x, ok := <-products
if !ok {
log.Panicf("Expecting more products")
}
tmp.Mul(x, x)
x.Rem(y, tmp)
output <- x
x, ok = <-products
if ok {
tmp.Mul(x, x)
x.Rem(y, tmp)
output <- x
}
y.Clear()
}
}
// For each input modulus 'x' and remainderTree parent 'y', compute z = (y%(x*x))/x; gcd(z, x)
func remainderTreeFinal(lastLevel, moduli []*gmp.Int, output chan<- Collision, wg *sync.WaitGroup, start, step int) {
tmp := new(gmp.Int)
for i := start; i < len(moduli); i += step {
modulus := moduli[i]
y := lastLevel[i/2]
tmp.Mul(modulus, modulus)
tmp.Rem(y, tmp)
tmp.Quo(tmp, modulus)
if tmp.GCD(nil, nil, tmp, modulus).BitLen() != 1 {
q := new(gmp.Int).Quo(modulus, tmp)
output <- Collision{
Modulus: modulus,
P: tmp,
Q: q,
}
tmp = new(gmp.Int)
}
}
wg.Done()
}
// This performs the GCD of the product of all previous moduli with the current one.
// This uses around double the memory (minus quite a lot of overhead), and identifies
// problematic input in O(n) time, but has to do another O(n) scan for each collision
// to figure get the private key back.
// If there are no collisions, this algorithm isn't parallel at all.
// If we get a GCD that is the same as the modulus, we do a manual scan for either colliding Q or identical moduli
// If we get a GCD lower than the modulus, we have one private key, then do a manual scan for others.
func MulAccumGCD(moduli []*gmp.Int, collisions chan<- Collision) {
accum := gmp.NewInt(1)
gcd := new(gmp.Int)
var wg sync.WaitGroup
for i, modulus := range moduli {
gcd.GCD(nil, nil, accum, modulus)
if gcd.BitLen() != 1 {
wg.Add(1)
if gcd.Cmp(modulus) == 0 {
go findGCD(&wg, moduli, i, collisions)
continue
} else {
go findDivisors(&wg, moduli, i, gcd, collisions)
gcd = new(gmp.Int)
}
}
accum.Mul(accum, modulus)
}
wg.Wait()
close(collisions)
}
func ExampleInt_SetString() {
i := new(big.Int)
i.SetString("644", 8) // octal
fmt.Println(i)
// Output: 420
}
// Rought square root of z.
func roughSqrt(z *big.Int) *big.Int {
return big.NewInt(0).Exp(big.NewInt(2), big.NewInt(int64((z.BitLen()+1)/2)), nil)
}
