[Cryptography] cryptography Digest, Vol 16, Issue 11

[Jerry Leichter]

On Aug 14, 2014, at 6:56 PM, Benjamin Kreuter <brk7bx at virginia.edu> wrote:
>> (There are vaguer hints that they have some similar design
>> secrets for stream ciphers:  No public stream cipher has survived
>> public attack, but while we don't know how they work internally, NSA
>> has continue to field stream ciphers for its own   use, so it
>> apparently thinks it can produce secure ones.)
> 
> Are you not counting OFB, CTR, or GCM mode as "stream ciphers?"  I do
> not see any meaningful distinction there.
Yes, you can turn any block cipher into a stream cipher.  But ciphers built as stream ciphers tend to have a simpler structure and give you much faster operation with less hardware.  The NSA seems to believe there's a meaningful distinction as they continue to produce both block and stream ciphers intended for different application domains.
                                                        -- Jerry