[russellsprouts]

But, if you use one-time pad correctly, then your string "HEADS TAILS HEADS HEADS" will be just as likely as any other string of the same length. "TAILS HEADS TAILS TAILS" would be just as likely, as would "MEETING AT MIDNIGHT. -E". This is because a one-time pad key has just as much entropy as the plaintext.

[codeflo]

Yes, there were some unstated assumptions in my argument, like the key being smaller than the plaintext. (For example, a typical symmetric key is 32 bytes long, and a typical plaintext at least several kilobytes.)