On 6/13/07, Siddhesh Poyarekar <[EMAIL PROTECTED]> wrote:
On 6/13/07, Dinesh Joshi <[EMAIL PROTECTED]> wrote:
> Get your facts straight before you reply. a message encrypted with a 128
> bit key DES is no more secure than a 64 bit key DES. Actually the length
> of the key is only 56 bit in the latter case.
Please cite a source for this. I'd like to know how DES is done with a
128 bit key.
The Data Encryption Standard (DES) implies the use of a 56 bit key.
Change the key length and you'll have to change multiple parameters of
the algorithm.
@Siddhesh: You're right. The two basic steps - substitution and
permutation - are designed carefully for 64 bit blocks. Increasing it
for higher number of bits will be non-trivial in that guaranteeing its
security is difficult.
@Dinesh: By definition, a brute-force attack is just cycling through
all the possible keys. Therefore, in general, greater the bits in the
key, the more combinations that require to be tested and hence harder
the brute-force attack. This is independent of DES or 3-DES or any
other key-based encryption algorithm.
Parijat
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