> For the complete documentation index, see [llms.txt](https://the-winrars.gitbook.io/writeups/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://the-winrars.gitbook.io/writeups/2020-writeups/ractf/crypto/access-0000.md).

# Access=0000

Basic CBC bit flipping - We're given ciphertext for `access=9999;`+ an expiry timestamp, and have to provide an IV and ciphertext that decrypt to `acesss=0000`.

<https://gchq.github.io/CyberChef/#recipe=From_Hex('Auto')XOR(%7B'option':'Hex','string':'0000000000003d393939390000000000'%7D,'Standard',true)XOR(%7B'option':'Hex','string':'0000000000003d303030300000000000'%7D,'Standard',true)To_Hex('None',0)&input=NjA3MDcwOTllNDlhYjdmOWU5NTY2NWRjZTg0ZDI4NmVhNTI0Yzc1N2JhYmNjN2QyMWI1YTlhYWU0OTY1NGY1ZGNjNGU0ZjZkZGY5ZTk1OTUxNThkYmQyMzYyMDhjMmU1>

## ractf{cbc\_b17\_fl1pp1n6\_F7W!}