IDF实验室:百密一疏--凯撒加密

 地址:

ctf.idf.cn/index.php?g=game&m=list&a=index&id=19

题目:

凯撒加密的

大概就是这样吧,不能告诉你再多了。。

U8Y]:8KdJHTXRI>XU#?!K_ecJH]kJG*bRH7YJH7YSH]*=93dVZ3^S8*$:8"&:9U]RH;g=8Y!U92'=j*$KH]ZSj&[S#!gU#*dK9\.



Writeup:

得知是凯撒加密之后,尝试进行127次轮转爆破:


lstr="""U8Y]:8KdJHTXRI>XU#?!K_ecJH]kJG*bRH7YJH7YSH]*=93dVZ3^S8*$:8"&:9U]RH;g=8Y!U92'=j*$KH]ZSj&[S#!gU#*dK9\."""

for p in range(127):
	str1 = ''
	for i in lstr:
		temp = chr((ord(i)+p)%127)
		if 32

得出的有用部分如下:

U8Y]:8KdJHTXRI>XU#?!K_ecJH]kJG*bRH7YJH7YSH]*=93dVZ3^S8*$:8"&:9U]RH;g=8Y!U92'=j*$KH]ZSj&[S#!gU#*dK9\.
V9Z^;9LeKIUYSJ?YV$@"L`fdKI^lKH+cSI8ZKI8ZTI^+>:4eW[4_T9+%;9#';:V^SI9Z"V:3(>k+%LI^[Tk'\T$"hV$+eL:]/
W:[_<:MfLJVZTK@ZW%A#MageLJ_mLI,dTJ9[LJ9[UJ_,?;5fX\5`U:,&<:$(<;W_TJ=i?:[#W;4)?l,&MJ_\Ul(]U%#iW%,fM;^0
X;\`=;NgMKW[ULA[X&B$NbhfMK`nMJ-eUK:\MK:\VK`-@<6gY]6aV;-'=;%)=j@;\$X<5*@m-'NK`]Vm)^V&$jX&-gN<_1
Y<]a><&*>=YaVL?kA<]%Y=6+An.(OLa^Wn*_W'%kY'.hO=`2
Z=^b?=PiOMY]WNC]Z(D&PdjhOMbpOL/gWM<^OM<^XMb/B>8i[_8cX=/)?='+?>ZbWM@lB=^&Z>7,Bo/)PMb_Xo+`X(&lZ(/iP>a3
[>_c@>QjPNZ^XOD^[)E'QekiPNcqPM0hXN=_PN=_YNc0C?9j\`9dY>0*@>(,@?[cXNAmC>_'[?8-Cp0*QNc`Yp,aY)'m[)0jQ?b4
\?`dA?RkQO[_YPE_\*F(RfljQOdrQN1iYO>`QO>`ZOd1D@:k]a:eZ?1+A?)-A@\dYOBnD?`(\@9.Dq1+ROdaZq-bZ*(n\*1kR@c5
]@aeB@SlRP\`ZQF`]+G)SgmkRPesRO2jZP?aRP?a[Pe2EA;l^b;f[@2,B@*.BA]eZPCoE@a)]A:/Er2,SPeb[r.c[+)o]+2lSAd6
^AbfCATmSQ]a[RGa^,H*ThnlSQftSP3k[Q@bSQ@b\Qf3FBoae>i^C5/EC-1ED`h]SFrHCd,`D=2Hu5/VShe^u1f^.,r`.5oVDg9
aDeiFDWpVT`d^UJda/K-WkqoVTiwVS6n^TCeVTCe_Ti6IE?pbf?j_D60FD.2FEai^TGsIDe-aE>3Iv60WTif_v2g_/-sa/6pWEh:
bEfjGEXqWUae_VKeb0L.XlrpWUjxWT7o_UDfWUDf`Uj7JF@qcg@k`E71GE/3GFbj_UHtJEf.bF?4Jw71XUjg`w3h`0.tb07qXFi;
cFgkHFYrXVbf`WLfc1M/YmsqXVkyXU8p`VEgXVEgaVk8KGArdhAlaF82HF04HGck`VIuKFg/cG@5Kx82YVkhax4ia1/uc18rYGj<

eHimJH[tZXdhbYNhe3O1[ousZXm{ZW:rbXGiZXGicXm:MICtfjCncH:4JH26JIembXKwMHi1eIB7Mz:4[Xmjcz6kc31we3:t[Il>
fIjnKI\u[YeicZOif4P2\pvt[Yn|[X;scYHj[YHjdYn;NJDugkDodI;5KI37KJfncYLxNIj2fJC8N{;5\Ynkd{7ld42xf4;u\Jm?
gJkoLJ]v\Zfjd[Pjg5Q3]qwu\Zo}\Y

仔细观察,发现倒数第5行是一串Base64加密,解密得

'the flag is wctf{kaisa_jiaaaaami},plz flow my weibo,http://weibo.com/woldy'

flag = wctf{kaisa_jiaaaaami}

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