对目标文件进行加密解密文件，按字节来加密解密。对于1G文件，可以在几秒钟内完成加密解密。-File encryption and decryption of the target file, byte by byte encryption and decryption. For 1G file, it can be completed within a few seconds of encryption and decryption.

C# code encrypt and decrypt string by some method