user38324: Given a 12 or 24 word seed with one one or more missing words what would be the difficulty of brute-forcing the missing words? E.g. for: 

one missing word
two missing words
three missing words

By difficulty I mean the number of permutations against a dictionary wordlist. 
And the related question: how many words would have to be missing in order to make the attack reliably unfeasible?

user65907: Missing 3 words in known positions and there will be 8.577.355.766 permutations.
Based on the speed of an average PC, approximately 10 permutations/second. This would take close to 9927 years(if unlucky and have to try every permutations) Sorry, I forgot we are not dealing with wallet password encryption here.
Anyway, a computer will have to get the private key, calculate a public key and then check it for balance, this process will take time.
Missing 4 words(17.540.692.561.920 permutations) or more, and I don't think anyone will want to try their luck. So maybe 5 words or more and even the government will let it slide.

user113896: A wallet was brute forced with 8/12 words and their order known in 2020
https://medium.com/@johncantrell97/how-i-checked-over-1-trillion-mnemonics-in-30-hours-to-win-a-bitcoin-635fe051a752

38324: <p>Given a 12 or 24 word seed with one one or more missing words what would be the difficulty of brute-forcing the missing words? E.g. for: </p>

<ul>
<li>one missing word</li>
<li>two missing words</li>
<li>three missing words</li>
</ul>

<p>By difficulty I mean the number of permutations against a dictionary wordlist. </p>

<p>And the related question: how many words would have to be missing in order to make the attack reliably unfeasible?</p>
 65907: <p>Missing 3 words in known positions and there will be <a href="https://www.calculatorsoup.com/calculators/discretemathematics/permutations.php" rel="nofollow noreferrer">8.577.355.766 permutations</a>.<br>
<s>Based on the speed of an average PC, approximately 10 permutations/second. This would take close to 9927 years(if unlucky and have to try every permutations)</s> Sorry, I forgot we are not dealing with wallet password encryption here.</p>

<p>Anyway, a computer will have to get the private key, calculate a public key and then check it for balance, this process will take time.<br>
Missing 4 words(17.540.692.561.920 permutations) or more, and I don't think anyone will want to try their luck. So maybe 5 words or more and even the government will let it slide.</p>
 113896: <p>A wallet was brute forced with 8/12 words and their order known in 2020</p>
<p><a href="https://medium.com/@johncantrell97/how-i-checked-over-1-trillion-mnemonics-in-30-hours-to-win-a-bitcoin-635fe051a752" rel="nofollow noreferrer">https://medium.com/@johncantrell97/how-i-checked-over-1-trillion-mnemonics-in-30-hours-to-win-a-bitcoin-635fe051a752</a></p>
