<p>My crude understanding is:</p>
<p>What is a VFR?</p>
<blockquote>
<p>&quot;A Verifiable Random Function (VRF) [MRV99] is the public-key version
of a keyed cryptographic hash.  Only the holder of the private VRF<br />
key can compute the hash, but anyone with corresponding public key<br />
can verify the correctness of the hash.&quot; <a href="https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-vrf-03" rel="nofollow noreferrer">Ref 1</a></p>
</blockquote>
<ol>
<li>What are Block and Leader VRF values?</li>
</ol>
<blockquote>
<p>In the Leader Log, assigned blocks are chosen by their VRF values or score. The
pools with the lowest VFR wins (Andrew Westberg described it as, who
can do the lowest Limbo).</p>
</blockquote>
<ol start="2">
<li>How do they relate to the winners/losers of slot battles and/or height battles?</li>
</ol>
<blockquote>
<p>In the case of slot or height battles, the pool with the lowest VRF
wins. It use to be the case that small pools had a slight advantage
for slot/height battles. In the Vasil upgrade (Praos), that is no
longer the case <a href="https://github.com/input-output-hk/ouroboros-network/issues/4051" rel="nofollow noreferrer">Ref 2</a></p>
</blockquote>
<p>The source of truth is the <a href="https://hydra.iohk.io/build/20980576/download/1/ledger-spec.pdf" rel="nofollow noreferrer">Shelley Ledger Spec</a>.</p>

CC BY-SA 4.0
2022-11-05T02:08:46.560Z
2022-11-05T02:08:46.560Z
TheStophe
<p>During slot battles or height battles between stake pools, the <a href="https://pooltool.io/realtime" rel="nofollow noreferrer">realtime chain tip</a> on Pooltool displays (B) and (L) for the pool that has a lower &quot;Block&quot; and &quot;Leader&quot; VRF value, respectively. <a href="https://pooltool.io/realtime/7960162" rel="nofollow noreferrer">Here</a> is an example of one such instance (height battle).</p>
<p>My question is twofold:</p>
<ol>
<li>What are Block and Leader VRF values?</li>
<li>How do they relate to the winners/losers of slot battles and/or height battles?</li>
</ol>

<stake-pool><ouroboros>
What are Leader VRF and Block VRF values on Pooltool?
# What are Leader VRF and Block VRF values on Pooltool?

(Asked by: username_0 on 2022-11-02)

During slot battles or height battles between stake pools, the [realtime chain tip](https://pooltool.io/realtime) on Pooltool displays (B) and (L) for the pool that has a lower "Block" and "Leader" VRF value, respectively. [Here](https://pooltool.io/realtime/7960162) is an example of one such instance (height battle).

My question is twofold:

1. What are Block and Leader VRF values?
2. How do they relate to the winners/losers of slot battles and/or height battles?

**Tags:** stake-pool, ouroboros

---

## 1 answers

### Answer by username_1 on 2022-11-05. Score: 1

My crude understanding is:

What is a VFR?

> "A Verifiable Random Function (VRF) [MRV99] is the public-key version
> of a keyed cryptographic hash. Only the holder of the private VRF  
> key can compute the hash, but anyone with corresponding public key  
> can verify the correctness of the hash." [Ref 1](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-vrf-03)

1. What are Block and Leader VRF values?

> In the Leader Log, assigned blocks are chosen by their VRF values or score. The
> pools with the lowest VFR wins (Andrew Westberg described it as, who
> can do the lowest Limbo).

2. How do they relate to the winners/losers of slot battles and/or height battles?

> In the case of slot or height battles, the pool with the lowest VRF
> wins. It use to be the case that small pools had a slight advantage
> for slot/height battles. In the Vasil upgrade (Praos), that is no
> longer the case [Ref 2](https://github.com/input-output-hk/ouroboros-network/issues/4051)

The source of truth is the [Shelley Ledger Spec](https://hydra.iohk.io/build/20980576/download/1/ledger-spec.pdf).


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