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Consider a variant of DSA in which the message space is $\mathbb Z_q$ and the hash function is replaced by the identity function. (So the second component of the signature is now $s := k^{−1} \cdot ( m + xr ) \mod q $). Show that this variant is not secure.

How would one go about this problem?

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  • $\begingroup$ Possible duplicate of crypto.stackexchange.com/questions/44862/… $\endgroup$ – Bissi Jan 23 '19 at 20:16
  • $\begingroup$ @badoo Feel free to remove questions once you've found a duplicate with a good answer otherwise it takes time out of everybody that's doing the review rounds. I'll vote it up before closing it so you can upvote the other question/answers. $\endgroup$ – Maarten Bodewes Jan 24 '19 at 12:12

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