Re: [ANN] Lua 5.2.0 (work5) now available

[Alistair Lynn <arplynn@...>]

Hi-

Emulating 64-bit bitwise operations with pairs of 32-bit values is fairly trivial.

Alistair

On 6 Nov 2010, at 03:29, pj@pjb.com.au wrote:

> Joseph Stewart wrote:
>> but what can't you do with 32-bit values that you need to do?
> 
> I wrote:
>> Strong encryption ?
>> In block cyphers, you need lots of XOR ops, and block sizes of
>> 32 bits are inherently vulnerable but 64 bits are very tough...
> 
> Rob Kendrick wrote:
>> It's difficult to see how simply doubling the number of bits
>> you process at once removes an inherent vulnerability.
> 
> See:   http://en.citizendium.org/wiki/Code_book_attack
> 
>  DES and the generation of ciphers that followed it all used a 64-bit
>  block size. To completely break a single key, an attacker would need
>  a code book with 2^64 entries. Even to weaken it significantly takes
>  a code book with 2^32 entries with the same key, 32 gigabytes of data.
>  With any sensible re-keying policy, a code book attack is not a threat.
>  More recent ciphers such as AES use a 128-bit block size,
>  which makes code book attacks utterly impractical.
> 
> The algorithms we use down here at the consumer-level are still
> 64-bit-block-size, see e.g.:
>  http://www.kremlinencrypt.com/algorithms.htm
> 
> Michal Kottman wrote:
>> encryption in pure Lua - of course you CAN do it, but IMHO it is better
>> to "leave it to the experts" and use existing cryptography libraries,
>> like OpenSSL (which even come with cryptography hardware support).
>> ... luacrypto (http://github.com/mkottman/luacrypto - my fork ...)
> 
> Cryptography is fun...
> 
> Regards,  Peter Billam
> 
> http://www.pjb.com.au       pj@pjb.com.au      (03) 6278 9410
> "Was der Meister nicht kann,   vermöcht es der Knabe, hätt er
> ihm immer gehorcht?"   Siegfried to Mime, from Act 1 Scene 2
> 
>