.Net 3.5，在进程之间传递字符串的最安全方式

I'd like to be able to pass a SecureString (a cached passphrase) to a child process in C# (.Net 3.5), but I don't know what the most secure way is to do it. If I were to convert the SecureString back to a regular string and pass it as a command-line argument, for example, then I I'd like to be able to pass a SecureString (a c