[Cryptography] 3DES security?

[Derek Atkins]

Henry,

On Wed, August 26, 2015 8:07 pm, Henry Baker wrote:
> What's the current best estimate for the (in)security of 3DES, in bits ?

2-key or 3-key 3DES?  Generally 3DES implies 2-key EDE, which equates to
112-bit security.  3-Key 3DES uses more key bits, but my recollection is
that it doesn't significantly increase the security..  So I would treat
3DES as 112-bit security.  To date, the best known attack against DES is
brute force.

The REAL issue with 3DES is that it's still only a 64-bit block size so
you have a 1 in 2^64 chance of randomly guessing the mapping from a
plaintext block to a cipher block, regardless of the keys.  Of course you
need to repeat this mapping on every block, so it doesn't necessarily buy
you anything.

-derek

-- 
       Derek Atkins                 617-623-3745
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       Computer and Internet Security Consultant