"It's tough to imagine how to start such a problem when you can't even rely on the ciphertext being correct." That's a common problem in the real world. A lot

"It's tough to imagine how to start such a problem when you can't even rely on the ciphertext being correct." That's a common problem in the real world. A lot of ciphertext, at least historically, comes from radio signals and if your receiver doesn't get a good copy of the signal you've got what you've got.