一. Base64加密原理：(摘自小聰大牛的博客)
把每三個字符，共24位2進制的ASCII碼，折分成連續4個6位的ASCII碼，再在每個ASCII碼前面補00變成8位， 最後對應一個碼錶來變成編碼字符：
碼錶爲（從0～63分別依次對應）：
0對應A………………………………………………………………………………63對應/
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
如果最後不夠3位數，則補0，這時後面對應的編碼是“=”
例：原文： a b c
ASCII碼： 01100001 | 01100010 | 01100011
分成4個： 011000 | 010110 | 001001 | 100011
補足位數： 00011000 | 00010110 | 00001001 | 00100011
數值大小： 24 22 9 35
對應編碼： Y W J j
編碼結果： YWJj
如果只有ab兩個字符，則第三個字符用全0來代替，這時結果爲YWI=
其實按照算法，=對應的編碼其實也可以認爲是爲0，所以QQ==和QQAA用來解密的話，都是A，但是後面補0時用“=”是加密算法自己的設置，所以加密結果只能是QQ==而不會是QQAA
知道了加密原理，解密原理就反其道而行之就行了，呵呵……
二. 加密特徵：
大小寫字母及數字混排，末尾可能包含等號
三. Base64解密方法：
我們還是以一個實例來簡單講解base64解密方法，在實際的網馬解密中，這種加密方式很少見。今天我們提供一種解密的方法，
在這裏用到的解密工具爲：notepad++ 這個軟件(附件爲notepad++)。後續我們還會講解使用一些其他的解密工具來解密base64。
npp_5.4.5.0.rar (2.83 MB, 下載次數: 83)
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
將上述代碼複製粘貼到notepad++，詳細步驟參看下例截圖：
接下來ctrl+a選中代碼，
點擊TextFX菜單下TextFXTools下的Base64 Decode後，
點擊file下的save as(另存爲)，將代碼保存爲擴展名爲txt(文件名任意)的文件。
直接打開保存好的文檔即可看到解密後的內容。
最終的解密結果相見下圖，紅色框中內容均爲病毒的下載地址(可能已失效)：
