On 10/27/2012 06:30 PM, Michael Zintakis wrote:
Maybe a bit daft of me to ask this, but is it possible to calculate a
hash on a stream of bytes where the resulting hash is considered to be
part of that stream?
In other words, lets assume that I have a stream which is, say, 64
bytes long in total, consisting of 48 bytes of "payload", plus 16-byte
for the hash and that hash has been calculated based on the *entire*
stream (payload+hash) of 64 bytes. Would that be possible to produce
with openssl or is this a bit of a chicken-and-egg scenario? Thanks!
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By its nature, a hash completely changes if just a bit of the original
content is modified, that also includes appending anything to it.
Any change will make the difference unpredictable.
My guess is that if you could write a hash working the way you say, it
would be vulnerable to all sorts of cryptographic attacks: give up!
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