題目連結
https://learn.cylabacademy.org/library/371
題目解法
下載後得到以下字串
VmpGU1EyRXlUWGxTYmxKVVYwZFNWbGxyV21GV1JteDBUbFpPYWxKdFVsaFpWVlUxWVZaS1ZWWnVh
RmRXZWtab1dWWmtSMk5yTlZWWApiVVpUVm10d1VWZFdVa2RpYlZaWFZtNVdVZ3BpU0VKeldWUkNk
MlZXVlhoWGJYQk9VbFJXU0ZkcVRuTldaM0JZVWpGS2VWWkdaSGRXCk1sWnpWV3hhVm1KRk5XOVVW
VkpEVGxaYVdFMVhSbFZrTTBKVVZXcE9VazFXV2toT1dHUllDbUY2UWpSWk1GWlhWa2RHZEdWRlZs
aGkKYlRrelZERldUMkpzUWxWTlJYTkxDZz09Cg==
看到用兩個等於結尾且內容皆為字母及數字，推測使用 base64 編碼，解碼後得到以下字串
VjFSQ2EyTXlSblJUV0dSVllrWmFWRmx0TlZOalJtUlhZVVU1YVZKVVZuaFdWekZoWVZkR2NrNVVX
bUZTVmtwUVdWUkdibVZXVm5WUgpiSEJzWVRCd2VWVXhXbXBOUlRWSFdqTnNWZ3BYUjFKeVZGZHdW
MlZzVWxaVmJFNW9UVVJDTlZaWE1XRlVkM0JUVWpOUk1WWkhOWGRYCmF6QjRZMFZXVkdGdGVFVlhi
bTkzVDFWT2JsQlVNRXNLCg==
在解碼一次得到
V1RCa2MyRnRTWGRVYkZaVFltNVNjRmRXYUU5aVJUVnhWVzFhYVdGck5UWmFSVkpQWVRGbmVWVnVR
bHBsYTBweVUxWmpNRTVHWjNsVgpXR1JyVFdwV2VsUlZVbE5oTURCNVZXMWFUd3BTUjNRMVZHNXdX
azB4Y0VWVGFteEVXbm93T1VOblBUMEsK
在解碼一次得到
WTBkc2FtSXdUbFZTYm5ScFdWaE9iRTVxVW1aaWFrNTZaRVJPYTFneVVuQlpla0pyU1ZjME5GZ3lV
WGRrTWpWelRVUlNhMDB5VW1aTwpSR3Q1VG5wWk0xcEVTamxEWnowOUNnPT0K
在解碼一次得到
Y0dsamIwTlVSbnRpWVhObE5qUmZiak56ZEROa1gyUnBZekJrSVc0NFgyUXdkMjVzTURSa00yUmZO
RGt5TnpZM1pESjlDZz09Cg==
在解碼一次得到
cGljb0NURntiYXNlNjRfbjNzdDNkX2RpYzBkIW44X2Qwd25sMDRkM2RfNDkyNzY3ZDJ9Cg==
在解碼一次得到 flag
picoCTF{bas------------------------------------7d2}