user1652: I've generated a private key using vanitygen command by:
$ ./vanitygen 11
Difficulty: 256
Pattern: 11                                                                    
Address: 114beUkusDnzqxif5BbESZMNo6T5N27...
Privkey: 5JeApQGQCCEp1K3rjXr8vDcEWMFw2Agzj2YZnN51zZC37Sw7...

Is it possible to convert a generated Privkey to BIP39 mnemonic words or entropy (hex)?
As the app/wallet which I'm using only accept BIP39 mnemonic words to import a wallet and I would like to create a wallet using a vanitygen utility.

user13866: So far as I know this isn't possible.
The mnemonic phrase is hashed to get a seed number. Hashing algorithms are one-way algorithms.
See BIP39

To create a binary seed from the mnemonic, we use the PBKDF2 function with a mnemonic sentence (in UTF-8 NFKD) used as the password and the string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt. The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function. The length of the derived key is 512 bits (= 64 bytes).


This seed can be later used to generate deterministic wallets using BIP-0032 or similar methods.


Related:
is PBKDF2 reversible?

1652: <p>I've generated a private key using <a href="https://github.com/exploitagency/vanitygen-plus" rel="nofollow noreferrer"><code>vanitygen</code> command</a> by:</p>
<pre><code>$ ./vanitygen 11
Difficulty: 256
Pattern: 11                                                                    
Address: 114beUkusDnzqxif5BbESZMNo6T5N27...
Privkey: 5JeApQGQCCEp1K3rjXr8vDcEWMFw2Agzj2YZnN51zZC37Sw7...
</code></pre>
<p>Is it possible to convert a generated Privkey to BIP39 mnemonic words or entropy (hex)?</p>
<p>As the app/wallet which I'm using only accept BIP39 mnemonic words to import a wallet and I would like to create a wallet using a <code>vanitygen</code> utility.</p>
 13866: <p>So far as I know this isn't possible.</p>
<p>The mnemonic phrase is hashed to get a seed number. Hashing algorithms are one-way algorithms.</p>
<p>See <a href="https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki" rel="nofollow noreferrer">BIP39</a></p>
<blockquote>
<p>To create a binary seed from the mnemonic, we use the PBKDF2 function with a mnemonic sentence (in UTF-8 NFKD) used as the password and the string &quot;mnemonic&quot; + passphrase (again in UTF-8 NFKD) used as the salt. The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function. The length of the derived key is 512 bits (= 64 bytes).</p>
</blockquote>
<blockquote>
<p>This seed can be later used to generate deterministic wallets using BIP-0032 or similar methods.</p>
</blockquote>
<hr />
<p>Related:</p>
<p><a href="https://crypto.stackexchange.com/q/77513/52982">is PBKDF2 reversible?</a></p>
