Vidar

Inspired by encryption techniques used in the Vidar malware family, this challenge implements a cipher algorithm to protect its secrets.

You are provided with a compiled Linux binary that prompts for a decryption key. The encrypted data is stored as hex strings and split into two parts. Analyze the binary to understand the encryption mechanism and recover the flag.

Binary Information:

Filename: vidar
Size:     14,680 bytes (15 KB)
MD5:      16511258f6e4130ebfca591b6763b344
SHA1:     fd651cc39e88e9c101cc1ec0b72be3dfb628126e
SHA256:   08a14e293667f259a5a11f9f8e43e1dcee482430ad2d7ffac69ff9714fc3b7f4

Verify integrity after download:

md5sum vidar
sha1sum vidar
sha256sum vidar