求字符串加密方法

我有一个程序对字符串加密了，我有对应表，想求加密方法。
加密文                         原文
707EThwK7OQ=              2720.92500
BYYtZ/WjTvU=              2751.15800
IA==                         8.00000
ICna                         8.70000
ICnaww==                     8.79000
ICnay6I=                     8.71200
ICnay6Q=                     8.71400
ICnayA==                     8.72000
ICnayw==                     8.71000
ICnazA==                     8.76000
ICnazac=                     8.77700
ICnazg==                     8.74000
ICnazKg=                     8.76800
ICnazw==                     8.75000
ICnb                         8.60000
ICnbwg==                     8.68000
ICnbyag=                     8.63800
ICnbyaY=                     8.63600
ICnbyQ==                     8.63000
ICnbyw==                     8.61000
ICnbzA==                     8.66000
ICnbzQ==                     8.67000
ICnbzw==                     8.65000
ICnc                         8.10000
ICncyA==                     8.12000
ICncyaY=                     8.13600
ICncyKg=                     8.12800
ICncyQ==                     8.13000
ICncyw==                     8.11000
ICncz6E=                     8.15100
ICnczA==                     8.16000
ICnczag=                     8.17800
ICnczKQ=                     8.16400
ICnczw==                     8.15000
ICndwg==                     8.08000
ICndww==                     8.09000
ICndyKI=                     8.02200
ICndyQ==                     8.03000
ICndyqg=                     8.00800
ICndzA==                     8.06000
ICndzaM=                     8.07300
ICndzaQ=                     8.07400
ICndzaU=                     8.07500
ICndzg==                     8.04000
ICndzw==                     8.05000
ICne                         8.30000
ICneww==                     8.39000
ICney6c=                     8.31700
ICneyaE=                     8.33100
ICneyQ==                     8.33000
ICneyqQ=                     8.30400
ICneyw==                     8.31000
ICnez6k=                     8.35900
ICnezak=                     8.37900
ICnezg==                     8.34000
ICnezQ==                     8.37000
ICnezqQ=                     8.34400
ICnf                         8.20000
ICnfw6U=                     8.29500
ICnfwg==                     8.28000
ICnfww==                     8.29000
ICnfyA==                     8.22000
ICnfyKI=                     8.22200
ICnfyKM=                     8.22300
ICnfyKU=                     8.22500
ICnfyQ==                     8.23000
ICnfyw==                     8.21000
ICnfzaY=                     8.27600
ICnfzg==                     8.24000
ICnfzQ==                     8.27000
ICnfzw==                     8.25000
ICnU                         8.90000
ICnUwg==                     8.98000
ICnUwqg=                     8.98800
ICnUyA==                     8.92000