Rating: 5.0
# InCTF 2020 : DLPoly
**category** : crypto
**points** : 676
## write-up
```python
P.<x> = PolynomialRing(Zmod(p))
Q.<x> = QuotientRing(P, P.ideal(n))
g = x
print(bsgs(g, gX, (0, 2 ^ 56), operation='*'))
```
Use sagemath `bsgs` ( baby step giant step ) to brute force discrete logarithm.
But may run out of memory. I split it into 1024 sections and run each section paralleling using 8 core.
See `a.sh` and `b.sh` and `solve.sage` for details.
And then found that the length of flag is only 13 !??
The description also say something about RSA?
And I found that `n` has many small factor. But I got the flag before I reimplementing pohlig hellman algorithm.
## flag
`inctf{bingo!}`
# other write-ups and resources
