> Josh Berezin wrote:
>
> It's like this: I'm trying to figure out exactly what we're using here, so we can
>report it to Marketing-folk. I didn't write any of the SSL code, I'm just asking it a
>few questions.
>
> SSL_CIPHER_description reports we're using 3DES(168). Makes sense.
> SSL_CIPHER_get_bits() reports we're using 192 bits. (both in bits_used and
>bits_possible)
>
> So, which is right? 168 seems to make more sense, since DES is usually 56 bits, and
>168 is 56 * 3. But I guess it could be 192 == 64 * 3. What is the explanation for the
>discrepancy?
Parity, young man, parity. Each byte of the key has its own parity bit, which
makes DES's 64-bit key actually 56 bits, and 3DES's key 168 bits. The *effective*
key length of 3-DES-EDE-3K is actually about 112 bits, or what you might naively
assume to be the strength of 2DES.
The size of data block worked on depends on the mode, but DES is usually 64 bits...
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