matlab中ifndq,2015广州强网杯-Crypto-小心猪圈
注：本人纯小白，此题是看了很多writeup才明白并且复现的，只是为了巩固知识。
题目内容：
R29kIGpvYjo1NzY1NkM2QzIwNjQ2RjZFNjUzQTRBMzU1ODQ3NTkzNjRBNDE0RTM1NTg0NzRCNDk0NDU0NEY1MjUzNTg0MTQ5NDQ0MjRGMzU1MTU4NTM0RjUzNTI0NzQ5MzQ1ODRCNTc1MjU0NEE0QTU1NDc0OTUzNDM1NzRGNEU0RDU2NTE1NTU0NTE0RDQ5NUE0NDRCMzY1MzUwNEU1NTM0NTc1NTU5NEM0RjQ5NDkzMzU3NEIzMzRDNTU0RjQyNTI1NzMyMzQ0MjU0NEQ0QTRDNTQ1MTM1NDQ0MzQ3NEEzNDQ4NDc1OTRDNEE0NzQ2MzI1NzQ1NTYzMzU5NDc0RTQ3NDY0RjM0NDQ1NzRENTY0NDU3NTczNTQ0NDU0OTM0NTk1ODRENTk1MzQ4NDc1NjM0NTc0NTMzNEE1QTQ3NDI1MzQ3MzI0RDRDMzI0RDVBNDk1NDMyNTA0OTNE
分析：
一看就很迷，题说小心猪圈，首先想到猪圈密码。但这还有数字，所以貌似不能用。于是想到base64解码。
importbase64
test="R29kIGpvYjo1NzY1NkM2QzIwNjQ2RjZFNjUzQTRBMzU1ODQ3NTkzNjRBNDE0RTM1NTg0NzRCNDk0NDU0NEY1MjUzNTg0MTQ5NDQ0MjRGMzU1MTU4NTM0RjUzNTI0NzQ5MzQ1ODRCNTc1MjU0NEE0QTU1NDc0OTUzNDM1NzRGNEU0RDU2NTE1NTU0NTE0RDQ5NUE0NDRCMzY1MzUwNEU1NTM0NTc1NTU5NEM0RjQ5NDkzMzU3NEIzMzRDNTU0RjQyNTI1NzMyMzQ0MjU0NEQ0QTRDNTQ1MTM1NDQ0MzQ3NEEzNDQ4NDc1OTRDNEE0NzQ2MzI1NzQ1NTYzMzU5NDc0RTQ3NDY0RjM0NDQ1NzRENTY0NDU3NTczNTQ0NDU0OTM0NTk1ODRENTk1MzQ4NDc1NjM0NTc0NTMzNEE1QTQ3NDI1MzQ3MzI0RDRDMzI0RDVBNDk1NDMyNTA0OTNE"test=base64.b64decode(test)print test
得到结果：
God job:57656C6C20646F6E653A4A35584759364A414E3558474B4944544F525358414944424F355158534F5352474934584B5752544A4A5547495343574F4E4D56515554514D495A444B3653504E55345755594C4F494933574B334C554F425257323442544D4A4C5451354443474A344847594C4A4746325745563359474E47464F3444574D56445757354445493459584D5953484756345745334A5A47425347324D4C324D5A49543250493D
发现的到一个比较靠谱的16进制数，于是转换成文本，用HxD，将16进制数保存到一个txt中，用HxD打开
得到如下结果：
Well done:J5XGY6JAN5XGKIDTORSXAIDBO5QXSOSRGI4XKWRTJJUGISCWONMVQUTQMIZDK6SPNU4WUYLOII3WK3LUOBRW24BTMJLTQ5DCGJ4HGYLJGF2WEV3YGNGFO4DWMVDWW5DEI4YXMYSHGV4WE3JZGBSG2ML2MZIT2PI=
一看还是和base有关呀。于是在上一个脚本里再base
importbase64
test="R29kIGpvYjo1NzY1NkM2QzIwNjQ2RjZFNjUzQTRBMzU1ODQ3NTkzNjRBNDE0RTM1NTg0NzRCNDk0NDU0NEY1MjUzNTg0MTQ5NDQ0MjRGMzU1MTU4NTM0RjUzNTI0NzQ5MzQ1ODRCNTc1MjU0NEE0QTU1NDc0OTUzNDM1NzRGNEU0RDU2NTE1NTU0NTE0RDQ5NUE0NDRCMzY1MzUwNEU1NTM0NTc1NTU5NEM0RjQ5NDkzMzU3NEIzMzRDNTU0RjQyNTI1NzMyMzQ0MjU0NEQ0QTRDNTQ1MTM1NDQ0MzQ3NEEzNDQ4NDc1OTRDNEE0NzQ2MzI1NzQ1NTYzMzU5NDc0RTQ3NDY0RjM0NDQ1NzRENTY0NDU3NTczNTQ0NDU0OTM0NTk1ODRENTk1MzQ4NDc1NjM0NTc0NTMzNEE1QTQ3NDI1MzQ3MzI0RDRDMzI0RDVBNDk1NDMyNTA0OTNE"test=base64.b64decode(test)
test2="J5XGY6JAN5XGKIDTORSXAIDBO5QXSOSRGI4XKWRTJJUGISCWONMVQUTQMIZDK6SPNU4WUYLOII3WK3LUOBRW24BTMJLTQ5DCGJ4HGYLJGF2WEV3YGNGFO4DWMVDWW5DEI4YXMYSHGV4WE3JZGBSG2ML2MZIT2PI="test264=base64.b64decode(test2)
test232=base64.b32decode(test2)printtest264print test232
结果是：
'ﾕÆcﾢ@7ﾕÆ(ﾀÓ9 ﾗ
Only one step away:Q29uZ3JhdHVsYXRpb25zOm9janB7emtpcmp3bW8tb2xsai1ubWx3LWpveGktdG1vbG5ybm90dm1zfQ==
显然base32是可以的，但base64得不到正确结果。
看结果，果断继续。
importbase64
test="R29kIGpvYjo1NzY1NkM2QzIwNjQ2RjZFNjUzQTRBMzU1ODQ3NTkzNjRBNDE0RTM1NTg0NzRCNDk0NDU0NEY1MjUzNTg0MTQ5NDQ0MjRGMzU1MTU4NTM0RjUzNTI0NzQ5MzQ1ODRCNTc1MjU0NEE0QTU1NDc0OTUzNDM1NzRGNEU0RDU2NTE1NTU0NTE0RDQ5NUE0NDRCMzY1MzUwNEU1NTM0NTc1NTU5NEM0RjQ5NDkzMzU3NEIzMzRDNTU0RjQyNTI1NzMyMzQ0MjU0NEQ0QTRDNTQ1MTM1NDQ0MzQ3NEEzNDQ4NDc1OTRDNEE0NzQ2MzI1NzQ1NTYzMzU5NDc0RTQ3NDY0RjM0NDQ1NzRENTY0NDU3NTczNTQ0NDU0OTM0NTk1ODRENTk1MzQ4NDc1NjM0NTc0NTMzNEE1QTQ3NDI1MzQ3MzI0RDRDMzI0RDVBNDk1NDMyNTA0OTNE"test=base64.b64decode(test)
test2="J5XGY6JAN5XGKIDTORSXAIDBO5QXSOSRGI4XKWRTJJUGISCWONMVQUTQMIZDK6SPNU4WUYLOII3WK3LUOBRW24BTMJLTQ5DCGJ4HGYLJGF2WEV3YGNGFO4DWMVDWW5DEI4YXMYSHGV4WE3JZGBSG2ML2MZIT2PI="
#test264=base64.b64decode(test2)
test232=base64.b32decode(test2)
test3="Q29uZ3JhdHVsYXRpb25zOm9janB7emtpcmp3bW8tb2xsai1ubWx3LWpveGktdG1vbG5ybm90dm1zfQ=="test364=base64.b64decode(test3)print test364
得到结果：Congratulations:ocjp{zkirjwmo-ollj-nmlw-joxi-tmolnrnotvms}
ocjp{zkirjwmo-ollj-nmlw-joxi-tmolnrnotvms}和明显的flag{}格式，于是想到题目的猪圈密码。
百度一波有一个图
应用上图，左右两两相对，ocjp正好可以对应flag。
最后
importbase64
test="R29kIGpvYjo1NzY1NkM2QzIwNjQ2RjZFNjUzQTRBMzU1ODQ3NTkzNjRBNDE0RTM1NTg0NzRCNDk0NDU0NEY1MjUzNTg0MTQ5NDQ0MjRGMzU1MTU4NTM0RjUzNTI0NzQ5MzQ1ODRCNTc1MjU0NEE0QTU1NDc0OTUzNDM1NzRGNEU0RDU2NTE1NTU0NTE0RDQ5NUE0NDRCMzY1MzUwNEU1NTM0NTc1NTU5NEM0RjQ5NDkzMzU3NEIzMzRDNTU0RjQyNTI1NzMyMzQ0MjU0NEQ0QTRDNTQ1MTM1NDQ0MzQ3NEEzNDQ4NDc1OTRDNEE0NzQ2MzI1NzQ1NTYzMzU5NDc0RTQ3NDY0RjM0NDQ1NzRENTY0NDU3NTczNTQ0NDU0OTM0NTk1ODRENTk1MzQ4NDc1NjM0NTc0NTMzNEE1QTQ3NDI1MzQ3MzI0RDRDMzI0RDVBNDk1NDMyNTA0OTNE"test=base64.b64decode(test)
test2="J5XGY6JAN5XGKIDTORSXAIDBO5QXSOSRGI4XKWRTJJUGISCWONMVQUTQMIZDK6SPNU4WUYLOII3WK3LUOBRW24BTMJLTQ5DCGJ4HGYLJGF2WEV3YGNGFO4DWMVDWW5DEI4YXMYSHGV4WE3JZGBSG2ML2MZIT2PI="
#test264=base64.b64decode(test2)
test232=base64.b32decode(test2)
test3="Q29uZ3JhdHVsYXRpb25zOm9janB7emtpcmp3bW8tb2xsai1ubWx3LWpveGktdG1vbG5ybm90dm1zfQ=="test364=base64.b64decode(test3)
test4=test364[16:]
dic= {'a': 'j', 'b': 'k', 'c': 'l', 'd': 'm', 'e': 'n', 'f': 'o', 'g': 'p', 'h': 'q', 'i': 'r', 's': 'w', 'v': 'z','t': 'x', 'u': 'y', 'j': 'a', 'k': 'b', 'l': 'c', 'm': 'd', 'n': 'e', 'o': 'f', 'p': 'g', 'q': 'h', 'r': 'i','w': 's', 'z': 'v', 'x': 't', 'y': 'u'}
flag=''
for i intest4:if i indic:
flag+=dic[i]else:
flag+=iprint flag
运行得到结果。