> For the complete documentation index, see [llms.txt](https://rayyanwong.gitbook.io/rayyan/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rayyanwong.gitbook.io/rayyan/ctfs/lag-n-crash-2022-march/lnc2022-writeups/inverse-null-crypto.md).

# Inverse null ( Crypto )

![](https://lh6.googleusercontent.com/4l0YLX7XF4gT6uBciGXXyVot9DSYdDZqEtBTY-aHNmmjghEzdsMj6-Asrcn81QqFnmLPrscbTWFO3oND4J4TkS-LjBV1mufobyxwdIKJi-VaZaBZNLotcstx1JjtgaHHl_xoGD7-)

Given a string of what looks like a base64 ciphertext 

![](https://lh5.googleusercontent.com/VVNEOucxNM2m54yBo3pADRsvbdAn4-mDh7v2JvUPc66mRes-QU4Vj2ZXp19BlzecaBKXPomSNiGXib44UCOUhEQz3_ip-s2XhMYMQNRB_0UDlJWbHZCCGzXSzbqKhHy2_Pjx4u1b)

Since the challenge title already gave away the cipher, in this case null cipher. 

The null cipher is usually hiding the plain text with the first letter of each word in the paragraph. 

Since it is ‘inverse’, we take the last letter of each word to obtain the flag.

<mark style="color:blue;background-color:green;">**`LNC2022{SGSYLF}`**</mark>