###### The challenge text is as follows (line-separated for readability):
```Ypw'zj zwufpp hwu txadjkcq dtbtyu kqkwxrbvu! Mbz cjzg kv IAJBO{ndldie_al_aqk_jjrnsxee}. Xzi utj gnn olkd qgq ftk ykaqe uei mbz ocrt qi ynlu, etrm mff'n wij bf wlny mjcj :).```
###### We ran this text through a few ROT decoders, but weren’t able to get anything sensible out of it. However, looking again at the structure of the sentences, we knew that the flag would have to be in the format of `DUCTF{...}`. There was only one place in the text that had this pattern:
`IAJBO{ndldie_al_aqk_jjrnsxee}`
###### It seemed impossible for all the letters to be shifted the same way, but I pointed out that there could possibly multiple ciphers, i.e. each letter was shifted a different amount. Ruju wrote out the messages and noticed the same thing - in fact, we noticed that the ciphers increased by 1 each time (i.e., had a shifting i).
> D to I = 5
> A to U = 6
> J to C = 7
> B to T = 8
> O to F = 9.
###### With this in mind, we set to counting out some letters to form the flag. It took us a couple tries, but we ended up with:
`DUCTF{crypto_is_fun_kjqlptzy}`###### Which looked like it had to be a mistake. (What the hell is kjqlptzy?)
###### But it wasn’t.
**Flag**: `DUCTF{crypto_is_fun_kjqlptzy}`