[Cryptography] Severe flaw in all generality : key or nonce reuse

[John Denker]

On 10/17/2017 10:39 PM, Peter Gutmann wrote:
>   RC4 is a stream cipher for which key/nonce reuse results in a catastrophic
>   failure of the cryptosystem.
> 
>   GCM is a stream cipher for which key/nonce reuse results in a catastrophic
>   failure of the cryptosystem.

I hate to ask silly questions, but is there any cryptosystem or any
mode whatsoever where key/nonce reuse is acceptable?

It seems to me that chaining modes depend on the randomness of the
plaintext.  Unless you can reliably establish a hefty lower bound
the amount of such randomness --  which seems hard to do since the
plaintext is not known in advance -- using it as a substitute for
a random key/nonce seems exceedingly unsafe.