Tags: crypto forensics 

Rating: 0

Simple one, solved using zbarimg and stegosolve

We are given a qrcode result.png which when passed to zbarimg produces an equation.

```
kakdroog@kali:~/Documents/liveCTF/volgactf19/crypto/joi$ zbarimg result.png
QR-Code:C_F(n1, n2) = 14 * [C(n1,n2) / 14] + 7 * FLAG(n1,n2) + (C(n1,n2) mod 7)
scanned 1 barcode symbols from 1 images in 0.06 seconds
```

Guessed this to be a rabbit hole, thank fuck ;)

Fired up stegosolve and found working qrcode in RED Plane, saved as bmp and converted to png

```
kakdroog@kali:~/Documents/liveCTF/volgactf19/crypto/joi$ zbarimg solved.png
QR-Code:VolgaCTF{5t3g0_m4tr3shk4_in_4cti0n}
scanned 1 barcode symbols from 1 images in 0.06 seconds
```

YAY Flag!

> VolgaCTF{5t3g0_m4tr3shk4_in_4cti0n}