<p>How is the Schnorr Signature insecure in the following 2 scenarios:</p>

<ol>
<li><p>When there is no hash function used,
s = k-x*m mod q   <strong>instead of</strong>  s = k-x*H(m||r) mod q</p></li>
<li><p>When a hash function is defined as H(m) <strong>instead of</strong> H(m||r)</p></li>
</ol>

<p>Ref: <a href="http://en.wikipedia.org/wiki/Schnorr_signature" rel="nofollow">Schnorr Signature </a></p>

CC BY-SA 2.5
2011-02-24T04:12:13.443Z
This is a [homework](http://www.ics.uci.edu/~stasio/fall04/hmw5.pdf) question. Please note that in CSTheory, we only answer research-level questions. You can find the answer of your question in [Stinson's book](http://www.amazon.com/dp/1584885084/).
Sadeq Dousti
CC BY-SA 2.5
2011-02-24T04:30:36.613Z
@bala maverick, this site is for **research-level questions** in **theoretical computer science**, that are likely to have short well-defined answers. "Research-level" means, roughly, questions that might be discussed between two professors, or between graduate students working on Ph.D.'s, but not usually between a professor and the typical undergraduate student. It does not include questions at the level of difficulty of undergraduate homework. I am closing your question as off-topic since it is not a research level question.
Kaveh
CC BY-SA 3.0
2011-05-08T13:51:41.627Z
You could submit it to the IT security site.  http://security.stackexchange.com/
nealmcb
<cr.crypto-security>
Insecurity of Schnorr's Signature Scheme
bala maverick
# Insecurity of Schnorr's Signature Scheme

(Asked by: username_0 on 2011-02-23)

How is the Schnorr Signature insecure in the following 2 scenarios:

1. When there is no hash function used,
   s = k-x\*m mod q **instead of** s = k-x\*H(m||r) mod q
2. When a hash function is defined as H(m) **instead of** H(m||r)

Ref: [Schnorr Signature](http://en.wikipedia.org/wiki/Schnorr_signature)

**Tags:** cr.crypto-security

> **Comments:**
> **username_1**: This is a [homework](http://www.ics.uci.edu/~stasio/fall04/hmw5.pdf) question. Please note that in CSTheory, we only answer research-level questions. You can find the answer of your question in [Stinson's book](http://www.amazon.com/dp/1584885084/).  
> **username_2**: @username_0, this site is for **research-level questions** in **theoretical computer science**, that are likely to have short well-defined answers. "Research-level" means, roughly, questions that might be discussed between two professors, or between graduate students working on Ph.D.'s, but not usually between a professor and the typical undergraduate student. It does not include questions at the level of difficulty of undergraduate homework. I am closing your question as off-topic since it is not a research level question.  
> **username_3**: You could submit it to the IT security site.  http://security.stackexchange.com/  

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## 0 answers

