C#

<br />
--------<br />
PC1|AP1|<br />
--------<br />
AP2|AP1|<br />
--------<br />
RP1|PC4|<br />
--------<br />
AP2|PC4|<br />
--------

PC1-->AP1-->AP2-->PC4

public static bool EncryptFile(string inputFile, string outputFile)
		{
			PasswordDeriveBytes pdb = new PasswordDeriveBytes(fileEncryptionPassword, new System.Security.Cryptography.SHA384Managed().ComputeHash(new System.Text.UnicodeEncoding().GetBytes(fileEncryptionPassword)));
			byte[] key = pdb.GetBytes(32);
			byte[] IV = pdb.GetBytes(16);
			
			RijndaelManaged rm = new RijndaelManaged();
			rm.Key = key;
			rm.IV = IV;
			rm.BlockSize = 128;
			rm.Padding = PaddingMode.PKCS7;
			
			FileStream fsIn = new FileStream(inputFile, FileMode.Open, FileAccess.Read);
			FileStream fsOut = new FileStream(outputFile, FileMode.Create, FileAccess.Write);
			
			bool success = true;
			
			try{
				CryptoStream cs = new CryptoStream(fsOut, rm.CreateEncryptor(), CryptoStreamMode.Write);
				
				int bytesToWrite = 0;
				byte[] buffer = new byte[4096];
				
				while(true)
				{
					bytesToWrite = fsIn.Read(buffer, 0, buffer.Length);
					if(bytesToWrite == 0)
						break;
					cs.Write(buffer, 0, bytesToWrite);
				}
				
				cs.Close();
			}
			catch
			{
				success = false;
			}
			fsIn.Close();
			fsOut.Close();
			
			if(!success)
				File.Delete(outputFile);
			
			return success;
		}

public static bool DecryptFile(string inputFile, string outputFile)
		{
			PasswordDeriveBytes pdb = new PasswordDeriveBytes(fileEncryptionPassword, new System.Security.Cryptography.SHA384Managed().ComputeHash(new System.Text.UnicodeEncoding().GetBytes(fileEncryptionPassword)));
			byte[] key = pdb.GetBytes(32);
			byte[] IV = pdb.GetBytes(16);
			
			RijndaelManaged rm = new RijndaelManaged();
			
			rm.Key = key;
			rm.IV = IV;
			rm.BlockSize = 128;
			rm.Padding = PaddingMode.PKCS7;
			
			FileStream fsIn = new FileStream(inputFile, FileMode.Open, FileAccess.Read);
			FileStream fsOut = new FileStream(outputFile, FileMode.Create, FileAccess.Write);
			
			bool success = true;
			
			CryptoStream cs = new CryptoStream(fsIn, rm.CreateDecryptor(), CryptoStreamMode.Read);
			
			try{
				int bytesToWrite = 0;
				byte[] buffer = new byte[4096];
				
				while(true)
				{
					bytesToWrite = cs.Read(buffer, 0, buffer.Length);
					if(bytesToWrite == 0)
						break;
					fsOut.Write(buffer, 0, bytesToWrite);
				}
			}
			catch(Exception ex)
			{
				Debug.Show(ex.Message + "\n\n" + ex.StackTrace + "\n\n" + ex.InnerException.Message);
				success = false;
			}
			finally{
				cs.Close();
			}
			
			fsIn.Close();
			fsOut.Close();
			
			if(!success)
				File.Delete(outputFile);
			
			return success;
		}