how to encrypt and integrity-check with only one key

Zooko Wilcox-O'Hearn zooko at
Mon Sep 14 21:18:25 EDT 2009

following-up to my own post:

On Monday,2009-09-14, at 10:22 , Zooko Wilcox-O'Hearn wrote:

> David-Sarah Hopwood suggested the improvement that the integrity- 
> check value "V" could be computed as an integrity check (i.e. a  
> secure hash) on the K1_enc in addition to the file contents.

Oops, that's impossible.  What David-Sarah Hopwood actually said was  
that this would be nice if it were possible, but since it isn't then  
people should pass around the tuple of (v, K1_enc) whenever they want  
to verify the integrity of the ciphertext.



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