题目链接：攻防世界 (xctf.org.cn)

下载得到ogg文件。Olympic CTF 2014原题有提示120 LPM，对应Radiofax。需要将ogg格式文件转换成wav格式音频后，用OS X下的软件Multimode转换成单色传真图像：

文字部分为：

section 1 of 1 of file rfax_man

begin 644 rfax_man

h5sg60BSxwp62+57aMLVTPK3i9b-t+5pGLKyPA-FxxuysvFs+BT8+o0dVsM24

hcZHRaWYEHRBGFGtqk-cMV7oqqQRzbobGRB9Kwc-pTHzCDSSMJorR8d-pxdqd

hLWpvQWRv-N33mFwEicqz+UFkDYsbDvrfOC7tko5g1JrrSX0swhn64neLsohr

h26K1mSxnS+TF1Cta8GHHQ-t1Cfp7nh-oZeFuVi5MEynqyzX8kMtXcAynSLQx

hg4o56Pu4YUZHMqDGtczKeCwXU8PZEc4lY0FbDfFfgZpJFC-a-sHGLtGJgCMZ

hksr6XNTedEUdVJqxOO5VaReoH68eEPJ2m6d9mKhlhVE7zw4Yru4DUWRCJH28

hyeth+l2I0gPnEfrTLwAc+-TPS0YKYY3K0np58gVPgdAN8RY7+rQfRDin9JSa

hPG32WG7-rTl3uthvrnDO-wD09GDIRCniuoefs8UsfiWZOLq+0awOrQxAPM+C

hxLwOJ9VUKwdn7dJduLn1KhBucvL1pr5lGiBFfUbL79cFFex+G27kT+fsQ7X5

h87mgPivWhDSQHKPXqpKGniDkYsIYpg66ZWbHp4PfcgtPukElDWENlQPSuNAQ

hnboE4Bd8kyyokt67GgfGvBVS45sMFPtlgKRlG-QPFSgbMHujA3qYemxnuqGx

hp97aXpdKpvAE8zx-oUzazoVFz32X3OxAuiWJhKEjaYKpM7f95yv1S62v+k++

+

end

sum —r/size 7468/769 section (from "begin" to "end")

sum —r/size 36513/540 entire input file

这种每行均以小写h开头的密文很类似xxencode，解码后结果中有rfax_man.py字符串。用在线工具将解密结果保存为文件。根据其文件头1F 8B 08判定为gzip压缩包，解压得到rfax_man.py文件，内容为：

import socket,os,sys,hashlib

KEY  = "CTF{4BDF4498E4922B88642D4915C528DA8F}" # DO NOT SHARE THIS!
HOST = '109.233.61.11'
PORT = 8001
（后略）

KEY变量即为flag。

flag：CTF{4BDF4498E4922B88642D4915C528DA8F}