[Cryptography] Which big-name ciphers have been broken in living memory?

[Marc W. Abel]

On 08/16/2014 09:42 PM, Jerry Leichter wrote:
> Sending side:
> (We have cleartext block C1 ... Cn to send)
> 1.  Negotiate initial key K0.
> 2.  For i = 1 to n do
>        Ki = OneWayHash(K{i-1})
>        Destroy K{i-1}
>        send Enc(Ki, Ci)
>
> The receiving side is obvious.

Jerry, thank you!  I like it, although I see a notable distinction 
between this and the more traditional mechanisms for forward secrecy. 
This one doesn't appear to permit offline backups of master keys.

It might be that the only workaround is brute force; e.g., instead of 
having backups of a key, have backup /keys/.  And this could be doable. 
  But I'd love to hear any other approaches.

Marc