VPNs haven't been useful since 2002

[FlyingClayDisk]

The type of encryption they use on numbers stations is called a "one time pad". It's impossible to break because the key is unique every time and only know by the two parties communicating and is never sent over the air, only the contents of the cipher. Even if it is broken, only that message is decryptable, although this is theoretically impossible because the key is always random and bears no statistical relationship to the message.

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That is correct; it is a 'One Time Pad'.