/***************加密***************/
public void
Encryption()
{
FileStream fs1 = new FileStream(加密源文件的存放路径,
FileMode.Open, FileAccess.Read);
FileStream fs2 = new
FileStream(加密后文件的存放路径, FileMode.Create);
BinaryReader br1 = new
BinaryReader(fs1);
BinaryWriter br2 = new
BinaryWriter(fs2);
byte[] bys1 =
br1.ReadBytes((int)fs1.Length);
byte[] bys2 = new byte[(int)(bys1.Length)
* 2];
//加法加密
if ()
{
for (int i = 0, k = 0, j = 1; i < bys1.Length; i++, k = k + 2, j =
j + 2)
{
bys2[k] = (byte)((Convert.ToInt16(bys1[i]) +
Convert.ToInt16(参数（密钥）)) % 128 + 128);
bys2[j] =
(byte)((Convert.ToInt16(bys1[i]) + Convert.ToInt16(参数（密钥）)) /
128);
}
br2.Write(bys2);
}
//乘法加密
else
{
for
(int i = 0, k = 0, j = 1; i < bys1.Length; i++, k = k + 2, j = j +
2)
{
bys2[k] = (byte)((Convert.ToInt16(bys1[i]) *
Convert.ToInt16(参数（密钥）)) % 128 + 128);
bys2[j] =
(byte)((Convert.ToInt16(bys1[i]) * Convert.ToInt16(参数（密钥）)) /
128);
}
br2.Write(bys2);
}
br2.Close();
br1.Close();
}
/***************解密***************/
public void
Decryption()
{
FileStream fs1 = new FileStream(解密源文件的存放路径,
FileMode.Open, FileAccess.Read);
FileStream fs2 = new
FileStream(解密后文件的存放路径, FileMode.Create);
BinaryReader br1 = new
BinaryReader(fs1);
BinaryWriter br2 = new
BinaryWriter(fs2);
byte[] bys1 =
br1.ReadBytes((int)fs1.Length);
byte[] bys2 = new byte[(int)(bys1.Length)
/ 2];
//加法解密
if ()
{
for (int i
= 0, j = 1, k = 0; i < bys1.Length; i = i + 2, j = j + 2,
k++)
{
bys2[k] = (byte)(((Convert.ToInt16(bys1[i]) -
128) + (Convert.ToInt16(bys1[j]) * 128)) -
Convert.ToInt16(参数（密钥）));
}
br2.Write(bys2);
}
//乘法解密
else
{
for
(int i = 0,j=1,k=0; i < bys1.Length;
i=i+2,j=j+2,k++)
{
bys2[k] =
(byte)(((Convert.ToInt16(bys1[i]) - 128) + (Convert.ToInt16(bys1[j]) * 128)) /
Convert.ToInt16(参数（密钥）));
}
br2.Write(bys2);
}
br2.Close();
br1.Close();
}
