南京邮电大学CTF-密码学-mixed_base64

青旅半醒 2022-05-26 11:41 187阅读 0赞

题目如下：

![70][]

1.先把code.txt保存为一个文件

2.加密过程：

十次加密，每一次在base16，32，64中随机选择一种加密

3.解密过程：

用python直接尝试爆破

解密代码：

#*****题目：多重base64加密
    #*****python破解代码
    
    import base64
    
    def decode_mix_base64(b):
        a = b
       # print a
        i = 0
        while True:
            i = i+1
            print i
            #base16
            try:           
               c = base64.b16decode(a)
               a = c
               print('using base16 decode sucess.....')
               continue
            except:
                print ('using base16 decode failuer.....')
                pass      
            #base32
            try:
               c = base64.b32decode(a)
               a = c
               print('using base32 decode sucess.....')
               continue
            except:
                print ('using base32 decode failuer.....')
                pass
             #base64
            try:  
               c = base64.b64decode(a)
               a = c
               print('using base64 decode sucess.....')
               continue
            except:
                 print ('using base64 decode failuer.....')
                 pass     
            break
        print a
                
    def main():
        a = open('ctf_code_base64.txt')
        try:
            b = a.read()
        finally:
            a.close()
        #while True:
        try:
                #b = base64.b64decode(b)
            decode_mix_base64(b)
        except:
            print ('Finish!*********')
            #break
        
        
    if __name__ == '__main__':
        main()

运行程序破解flag

![70 1][]

ok，完成，拿到flag

[70]: /images/20220526/8f9a81d05c8c4bc587d3f07ea1a65341.png
[70 1]: /images/20220526/4783354729f34c4b82e3942a052afe6d.png